Patent Publication Number: US-11396744-B2

Title: Flush toilet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/JP2018/039431 filed Oct. 24, 2018, claiming priority to Japanese Patent Application No. 2017-220384, filed Nov. 15, 2017, and Japanese Patent Application No. 2018-031358, filed Feb. 23, 2018, the contents of each application being incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention generally relates to a flush toilet, and more particularly relates to a flush toilet having a structure for checking the backflow of water through a water supply path. 
     BACKGROUND ART 
     In a known flush toilet, a vacuum breaker is provided on a water supply path that connects a water discharge port for supplying water into a bowl to a water supply source (see, for example, Patent Literature 1). The vacuum breaker of Patent Literature 1 includes a water inlet port, a water outlet port, and an air inlet port. The vacuum breaker further includes a movable valve body for selectively allowing either the water inlet port and water outlet port, or the water outlet port and the air inlet port, to communicate with each other. The movable valve body moves while being guided along a guide shaft supported by a container to close either the water inlet port or the water outlet port by making tight contact with the valve seat at the peripheral edge of the water inlet or outlet port&#39;s opening. 
     Meanwhile, the water running through the water inlet port and the water outlet port sometimes contains minute dirt, dust, and other wastes (hereinafter referred to as “dirt and other wastes”), and therefore, the valve seat may sometimes collect such dirt and other wastes. If the movable valve body moves with the dirt and other wastes collected on the valve seat, then the dirt and other wastes may be trapped in the gap between the valve seat and the movable valve body, thus making the contact between the valve seat and the movable valve body insufficiently tight and eventually causing some failure. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2004-301326 A 
     SUMMARY OF INVENTION 
     It is therefore an object of the present invention to provide a flush toilet with a backflow check structure that does not easily cause failures. 
     A flush toilet according to an aspect of the present invention includes: a bowl to receive excreta; at least one water discharge port to discharge water into the bowl; a water supply path to supply the water from a water supply source to the water discharge port therethrough; and a backflow check structure provided for the water supply path to check a backflow of the water running through the water supply path. The backflow check structure has a water inlet port and a water outlet port. The water inlet port is exposed to the air and directly communicates with the water discharge port. The water outlet port channels the water supplied from the water supply source toward the water inlet port. The water inlet port is arranged on a trajectory of the water running out through the water outlet port. The water that has passed through the water inlet port is channeled directly toward the water discharge port. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a flush toilet according to an exemplary embodiment of an aspect of the present invention; 
         FIG. 2  is a perspective view illustrating a backflow check structure and a bowl of the flush toilet; 
         FIG. 3  is a cross-sectional view of the backflow check structure and its surrounding portions taken along a vertical plane; 
         FIG. 4  is a perspective view illustrating a backflow check structure and bowl according to a first variation; 
         FIG. 5  is a cross-sectional view of the backflow check structure and its surrounding portions taken along a vertical plane; 
         FIG. 6  is a side view of the backflow check structure and its surrounding portions; 
         FIG. 7  is a perspective view of a backflow check structure and its surrounding portions according to a second variation; and 
         FIG. 8  is a cross-sectional view of the backflow check structure and its surrounding portions taken along a vertical plane. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (1) Embodiment 
     A flush toilet  1  according to an exemplary embodiment is installed in a rest room  7  (or bath room) as shown in  FIG. 1 . The rear wall  74  of the rest room  7  is provided with a water supply pipe  71  as a water supply source and a water shut-off valve  72  is provided at one end of the water supply pipe  71 . Also, the floor  75  of the rest room  7  is provided with a drainpipe  73 . In this embodiment, when the flush toilet  1  is installed in the rest room  7 , a connecting member  6  is connected to the water shut-off valve  72  via a pipe  61  and a drainpipe  232  of a bowl  23  is connected to the drainpipe  73  via a drain trap  76 . Letting the water shut-off valve  72  communicate with the connecting member  6  allows the water to be supplied from the water supply source into the water supply path  3  of the flush toilet  1 . 
     The water supply pipe  71  according to this embodiment is a pipe branched from a water distributing pipe, leading to a distributing reservoir, toward each dwelling house. Therefore, the water supplied from the water supply pipe  71  as a water supply source has a certain water pressure. Actually, however, the water pressure varies to a certain degree according to the congestion of houses in a given area or hours of the day when the flush toilet  1  is used. In this embodiment, the water supply source includes the water shut-off valve  72  provided at the downstream end of the water supply pipe  71 . 
     According to the present disclosure, the water supply source does not have to be the water supply pipe  71  but may also be a water reservoir tank, for example. In that case, a pump may be installed in the rest room  7  to pump water from the tank using the pump. Alternatively, a tank may also be installed on the roof of a building so that water is channeled from the tank using potential energy. In short, the “water supply source” according to the present disclosure may be any type of source of the water to be supplied to the flush toilet  1 , no matter whether or not the water supply source has water pressure or whether or not the water supply source has a pump. 
     The flush toilet  1  according to this embodiment includes a toilet body  2 , the water supply path  3 , a backflow check structure  4 , and the connecting member  6 . In  FIG. 1 , a direction pointing from the flush toilet  1  toward the rear wall  74  of the rest room  7  and aligned with a horizontal plane is defined herein as a “backward direction” and the opposite direction thereof is defined herein as a “forward direction.” In addition, the rightward/leftward direction is defined with respect to a user who faces the flush toilet  1  from the front of the flush toilet  1  in the backward direction (see  FIG. 1 ). 
     The toilet body  2  forms the principal body of the flush toilet  1 . The toilet body  2  includes a plurality of outer parts  21 , an inner part  22 , a base  26 , a toilet seat (not shown), and a toilet lid  27 . 
     The plurality of outer parts  21  form the outer shell of the flush toilet  1 . These outer parts  21  are mounted on a frame (not shown) to form the outer shell of the flush toilet  1 . In this embodiment, the outer parts  21  include a skirt  211  supporting the inner part  22  thereon, a rear lower part  213  provided behind the skirt  211 , and a rear upper part  212  located over the rear lower part  213 . The toilet seat and the toilet lid  27  are mounted on the rear upper part  212  so as to be rotatable around a rightward/leftward axis. As used herein, the “rightward/leftward axis” refers herein to a rotational axis extending in the rightward/leftward direction, and may or may not have a shaft member. 
     The inner part  22  is a part arranged inside a space surrounded with the outer parts  21  and the toilet lid  27 . The inner part  22  is supported by an upper end portion of the skirt  211 . The inner part  22  includes the bowl  23 , a water discharge portion  25 , and a supporting portion  24  as shown in  FIG. 2 . 
     The bowl  23  is a part to receive excreta (i.e., urine and feces) discharged by the user. The bowl  23  is formed in the shape of a cup, of which the upper end is an opening and the lower end includes the drainpipe  232 . The inner surface of the bowl  23  (hereinafter referred to as a “bowl surface  231 ”) is tilted downward toward the front end of the drainpipe  232 . The water discharged from the water discharge portion  25  swirls around the vertical axis along the bowl surface  231 . As shown in  FIG. 1 , the rear end of the drainpipe  232  is connected via the drain trap  76  to the drainpipe  73  leading to a sewer. 
     As used herein, if the water “swirls” on the bowl surface  231 , it means that the water travels around the vertical axis along the inner surface of the bowl  23 . Therefore, the “swirl” of the water may naturally refer to a situation where the water makes one or more rounds about the vertical axis but may also refer to a situation where the water makes less than one round about the vertical axis as well. 
     The drain trap  76  is provided to prevent unpleasant odor from flowing back from the drainpipe  73  toward the bowl  23  and also prevent sanitary insects, for example, from attempting to enter the bowl  23  from the drainpipe  73 . The drain trap  76  may be implemented as a so-called “S-trap” which is an S-shaped pipe, or a movable trap, for example. The movable trap has its state switched by a motor, for example, from a state where the tip of its flexible pipe connected to the drainpipe  232  of the bowl  23  faces upward to a state where the tip of the flexible pipe faces downward, and vice versa. Optionally, the drain trap  76  may be replaced with an excreta tank including a pump. The excreta tank is connected to the drainpipe  232  and configured to drain excreta into the sewer using the pump. 
     The water discharge portion  25  is a portion for discharging water onto the inner surface of the bowl  23 . The water discharge portion  25  is arranged adjacent to the opening of the bowl  23 . The water discharge portion  25  includes a water discharge nozzle  251 , a pair of standup walls  252 , and a water discharge port  253 . 
     The water discharge nozzle  251  is a nozzle for discharging the water supplied through the water supply path  3 . The water discharge nozzle  251  is arranged between the pair of standup walls  252 . The pair of standup walls  252  guides the water discharged from the water discharge nozzle  251  so that the water swirls along the bowl surface  231 . The water discharge port  253  is a port through which the water is discharged onto the bowl  23 . In this embodiment, the water discharge port  253  is an opening facing toward the bowl  23  and configured to supply, onto the bowl  23 , the water that has been discharged from the water discharge nozzle  251  and guided by the pair of standup walls  252 . In this embodiment, the water discharge port  253  is implemented as an opening formed by the end of the standup wall  252  located inside of the bowl  23  and a part of the opposing standup wall  252  located outside of the bowl  23 , out of the pair of standup walls  252 . 
     In this embodiment, the water discharge port  253  is formed by the end of the standup wall  252  and a part of the opposing standup wall  252 . However, this is only an example and should not be construed as limiting. Alternatively, if the water discharge nozzle  251  faces the bowl surface  231 , then the opening at the tip of the water discharge nozzle  251  may be the water discharge port  253 . Also, the number of the water discharge port  253  provided does not have to be one. Alternatively, the single water discharge nozzle  251  may be configured to have a plurality of openings. Still alternatively, the water supply path  3  may be branched halfway and the water discharge nozzle  251  may be provided for each of the downstream end of the water supply path  3  and the downstream end of the branch path. Optionally, the opening may be configured as a hole. That is to say, as used herein, the “water discharge port  253 ” refers to a type of opening for discharging the water directly onto the bowl surface  231 . The flush toilet  1  according to the present disclosure may include at least one water discharge port  253 . 
     The supporting portion  24  is a portion extended outward from the outer edge of the surface surrounding the opening of the bowl  23  and supported by the upper end portion of the skirt  211 . The bowl  23  and the water discharge portion  25  are fixed via the supporting portion  24  onto the outer parts  21 . As used herein, the “upper end portion of the skirt  211 ” refers to a portion, covering a certain range from the top through a point lower than the top by a certain dimension, of the skirt  211 . 
     The base  26  is a part for mounting the backflow check structure  4  (to be described in detail later) onto an inner space of the rear upper part  212 . The base  26  is arranged inside the rear upper part  212 . 
     The water supply path  3  is a passage through which the water supplied from the water supply source is channeled toward the water discharge portion  25 . The upstream end of the water supply path  3  is connected to the connecting member  6 , while the downstream end of the water supply path  3  is connected to the water discharge nozzle  251 . The water supply path  3  is provided with a water supply valve (not shown). When the water supply valve opens, the water in the water supply path  3  starts running. When the water supply valve is closed, the water in the water supply path  3  stops running. In addition, in this embodiment, the water supply path  3  is provided with a constant flow valve (not shown) so that water flows at a constant flow rate. Thus, even if the water pressure of the water supplied from the water supply source varies to a certain degree, the water is discharged at a constant flow rate through the water discharge port  253  into the bowl  23 . 
     The water supply path  3  is provided with the backflow check structure  4 . The backflow check structure  4  checks the backflow of the water running through the water supply path  3 . This reduces, even if damage is done to the water supply path  3  when the level of the water run up in the bowl  23  rises so much as to immerse the water discharge portion  25  in the water that has run up, the chances of the water run up in the bowl  23  flowing back through the water supply path  3 . 
       FIG. 3  illustrates a cross section of the backflow check structure  4  and its surrounding portions taken along a vertical plane. As shown in  FIG. 3 , the backflow check structure  4  includes a water reservoir  41 , a water outlet pipe  46 , a splash reducing jacket  48 , a receiving vessel  49 , and a holder  51 . 
     The water reservoir  41  is a funnel with an opening exposed to the air (such an opening will be hereinafter referred to as an “air opening  43 ”), which is able to receive and run up a certain amount of water. At least part (e.g., all in this embodiment) of the water reservoir  41  is located above the upper end of the bowl  23 . The water reservoir  41  includes a cylindrical peripheral wall  44 , a bottom wall  45  formed at the lower end of the peripheral wall  44 , a water inlet pipe  42  provided for the bottom wall  45 , and a connecting pipe  47  connected to the lower end of the water inlet pipe  42 . 
     The peripheral wall  44  defines the outer wall of the water reservoir  41 . The peripheral wall  44  is formed in a cylindrical shape. The center axis  441  of the peripheral wall  44  is tilted with respect to a horizontal plane. As used herein, the “horizontal plane” refers to a plane that is parallel to the upper surface of the floor  75  (i.e., the floor surface) of the rest room  7 . In other words, the “horizontal plane” refers herein to a plane that is parallel to the plane including the lower end surface of the skirt  211  of the flush toilet  1 . 
     The bottom wall  45  defines the lower wall of the water reservoir  41  and is connected to the lower end of the peripheral wall  44 . The bottom wall  45  is formed in the shape of a truncated cone cylinder (i.e., a tapered shape). The center axis  452  of the bottom wall  45  is located on the extension of the center axis  441  of the peripheral wall  44 . That is to say, the center axis  452  of the bottom wall  45  is tilted with respect to the horizontal plane. The water inlet pipe  42  is connected to the bottom wall  45 . The center axis  422  of the water inlet pipe  42  is also located on the extension of the center axis  441  of the peripheral wall  44  and the center axis  452  of the bottom wall  45  (which will be hereinafter collectively referred to as the “center axis  410  of the water reservoir  41 ”). The upper surface of the bottom wall  45  (i.e., the inner surface, facing the water reservoir  41 , of the bottom wall  45  along the thickness thereof) defines a water guide surface  451  tilted downward toward the water inlet pipe  42 . 
     The water inlet pipe  42  is connected to the bottom wall  45 . The water inlet pipe  42  has a water inlet port  421  and communicates with the water reservoir  41  via the water inlet port  421 . The water inlet port  421  is an opening located at the upper longitudinal end of the water inlet pipe  42  and faces the internal space of the water reservoir  41 . In addition, the water inlet port  421  communicates directly with the water discharge port  253 . For example, in the example illustrated in  FIG. 2 , the connecting pipe  47  of the water reservoir  41  is connected to the water discharge portion  25  via only a pipe having no ports between both ends thereof (e.g., a flexible pipe). The surface surrounding the opening of the water inlet port  421  is a plane, which is tilted with respect to a vertical line and intersects at right angles with the center axis  410  of the water reservoir  41 . In this embodiment, the water inlet pipe  42  is implemented as a cylindrical pipe and the center axis  422  of the water inlet pipe  42  is tilted with respect to the horizontal plane. The center axis  422  of the water inlet pipe  42  is located on the extension of the center axis  410  of the water reservoir  41 . As used herein, the “vertical line” is a line perpendicular to the horizontal plane. Also, the center axis  422  of the water inlet pipe  42  passes through the center of the water inlet port  421 . In this embodiment, the surface surrounding the opening of the water inlet port  421  intersects with the center axis  422  at right angles. However, this is only an example and should not be construed as limiting. Alternatively, according to the present disclosure, the surface surrounding the opening of the water inlet port  421  may be tilted with respect to the center axis  422 . 
     Also, as used herein, if something “communicates directly with” something else, it means that the former and the latter communicate with each other without being exposed to the air. In this embodiment, the water inlet port  421  communicates with the water discharge port  253  via a pipe (or a tube) and no intermediate member such as a tank, for example, is provided between the water inlet port  421  and the water discharge port  253 . 
     The connecting pipe  47  is a portion, to which a pipe such as a tube for connecting the water discharge nozzle  251  to the water inlet pipe  42  is attached. The connecting pipe  47  is tilted with respect to the water inlet pipe  42 , and extends horizontally. The angle R formed between the connecting pipe  47  and the water inlet pipe  42  is an obtuse angle. 
     Over the water reservoir  41  with such a configuration, provided is a water outlet pipe  46  for pouring the water toward the water reservoir  41 . The water is supplied from the water supply source into the water outlet pipe  46 . The water outlet pipe  46  has a water outlet port  461 , through which the water supplied from the water supply source is poured into the water reservoir  41 . The water outlet pipe  46  has a center axis  462 , which passes through the center of the water outlet port  461 . 
     The water outlet port  461  is an opening at the lower end of the water outlet pipe  46 . The water running out through the water outlet port  461  passes through the space, which is exposed to the air, inside the backflow check structure  4 . The surface surrounding the opening of the water outlet port  461  is a plane, which is tilted with respect to a vertical line. Also, in this embodiment, the surface surrounding the opening of the water outlet port  461  intersects at right angles with the center axis  410  of the water reservoir  41 . The center of the water inlet port  421  is located on the extension of the center axis  462  passing through the center of the water outlet port  461 . Also, the center axis  462  is tilted with respect to the vertical line. Furthermore, in this embodiment, the surface surrounding the opening of the water outlet port  461  is parallel to the surface surrounding the opening of the water inlet port  421 . In this embodiment, the surface surrounding the opening of the water outlet port  461  intersects at right angles with the center axis  462 . However, this is only an example and should not be construed as limiting. Alternatively, according to the present disclosure, the surface surrounding the opening of the water outlet port  461  may be tilted with respect to the center axis  462 . 
     Thus, according to this embodiment, the water inlet port  421  is arranged on the trajectory of the water running out through the water outlet port  461 . Thus, the water running out through the water outlet port  461  directly enters the water inlet port  421 . As used herein, if the water running out through the water outlet port  461  “directly enters the water inlet port  421 ,” then it means that at least part (suitably most) of the water running out through the water outlet port  461  enters the water inlet port  421  without being guided into a groove, a pipe, a gutter, or any other guide member. 
     Therefore, the water running out through the water outlet port  461  enters the water inlet port  421  while substantially maintaining its initial velocity when the water left the water outlet port  461 , and then runs out through the water discharge port  253  while maintaining the impetus to a certain extent. This allows the flush toilet  1  according to this embodiment to discharge the water through the water discharge port  253  onto the bowl surface  231  while adequately maintaining the pressure of the water as supplied from the water supply source, even though the water is exposed to the air in the water reservoir  41 . As a result, a swirl flow may be formed on the bowl surface  231 . 
     The diameter of the water outlet port  461  is equal to or less than the diameter of the water inlet port  421 . In this embodiment, the diameter of the water outlet port  461  is suitably within the range from 30% to 100%, and more suitably within the range from 40% to 50%, of the diameter of the water inlet port  421 . 
     This allows the water running out through the water outlet port  461  to enter the water inlet port  421  more easily. In this embodiment, the surface surrounding the opening of the water outlet port  461  is tilted with respect to the vertical line, and therefore, the trajectory of the water running out through the water outlet port  461  draws a part of a parabola. However, since the diameter of the water outlet port  461  is restricted to the diameter of the water inlet port  421  or less, the water inlet port  421  is able to effectively receive the water running out through the water outlet port  461 . 
     The holder  51  holds the water outlet pipe  46  with respect to the water reservoir  41 . The holder  51  may hold the water outlet port  461  such that the water outlet port  461  is movable in a direction perpendicular to the surface surrounding the opening of the water inlet port  421 . This allows adjustments to be made such that the water running out through the water outlet port  461  enters the water inlet port  421  more effectively. 
     The backflow check structure  4  further includes the splash reducing jacket  48 . The splash reducing jacket  48  is a jacket with the ability to receive the water splashing toward the air opening  43  of the water reservoir  41 . The splash reducing jacket  48  is configured to channel the received water into the water reservoir  41 . Specifically, the splash reducing jacket  48  according to this embodiment is formed in the shape of cylinder with a top plate, and the lower end of the splash reducing jacket  48  is arranged inside the peripheral wall  44  of the water reservoir  41 . The backflow check structure  4  maintains the state of leaving a certain gap between the lower end of the splash reducing jacket  48  and the peripheral wall  44  of the water reservoir  41  and opening the gap to the air. 
     The splash reducing jacket  48  covers most of the air opening  43  of the water reservoir  41 . The splash reducing jacket  48  is fixed to the water outlet pipe  46  and configured to be movable along the center axis  410  of the water reservoir  41 . This makes the width of the gap between the splash reducing jacket  48  and the peripheral wall  44  of the water reservoir  41  adjustable. 
     In this embodiment, the lower end of the splash reducing jacket  48  is located, in the direction aligned with the center axis  410  of the water reservoir  41 , under the upper end of the water reservoir  41 . However, this is only an example and should not be construed as limiting. Alternatively, the lower end of the splash reducing jacket  48  may be located, in the direction aligned with the center axis  410  of the water reservoir  41 , over the upper end of the water reservoir  41 . That is to say, the splash reducing jacket  48  according to the present disclosure only needs to receive the water that has splashed by colliding against the inner surface of the water reservoir  41  or the water that has splashed directly from the water outlet pipe  46 . 
     The receiving vessel  49  surrounds the outer periphery of the water reservoir  41 . The receiving vessel  49  is formed in the shape of a bottomed cylinder, and is fixed to the water reservoir  41  such that its center axis  491  is aligned with the center axis  410  of the water reservoir  41  as shown in  FIG. 3 . The receiving vessel  49  is a vessel for receiving the water overflowing from the water reservoir  41 . The upper end surface of the receiving vessel  49  is located, in the direction defined by the center axis  410  of the water reservoir  41 , over the upper end surface of the water reservoir  41 . 
     An overflow pipe  50  is connected to the receiving vessel  49 . The overflow pipe  50  is connected to the bottom of the receiving vessel  49  to channel the water received at the receiving vessel  49  into the bowl  23 . The overflow pipe  50  is connected to the lowest portion (i.e., a portion located at the lowest level vertically) of the receiving vessel  49 . Thus, even when the level of the water run up in the bowl  23  rises so much as to immerse the water discharge portion  25  in the water that has run up and cause the water to flow backward into the water inlet pipe  42 , the water will flow back, through the gap between the lower end of the splash reducing jacket  48  and the peripheral wall  44  of the water reservoir  41 , into the receiving vessel  49 . Then, the water running into the receiving vessel  49  will be drained through the overflow pipe  50 . This reduces the chances of the water that has run up in the bowl  23  flowing backward into the water outlet pipe  46 . 
     The flush toilet  1  with such a configuration includes the connecting member  6  for connecting the water supply source to the water supply path  3  as shown in  FIG. 1 . The connecting member  6  is provided to be exposed on the outer parts  21  of the flush toilet  1 . In this embodiment, the connecting member  6  is a joint for connecting the pipe  61 . In this embodiment, the connecting member  6  is connected to the water shut-off valve  72  via a hose as the pipe  61 . The water that has passed through the connecting member  6  is channeled directly (i.e., via no intermediate members such as tanks) into the water outlet pipe  46  while maintaining its water pressure. As used herein, if “the water that has passed through the connecting member  6  is channeled directly through the water supply path  3 ,” then it means that the water that has passed through the connecting member  6  is channeled into the water outlet pipe  46  while maintaining its water pressure. In this embodiment, the water supply source has a water pressure, and therefore, the water maintaining the water pressure of the water supply source is channeled through the water supply path  3  into the water outlet pipe  46 . As used herein, the phrase “maintaining the water pressure” may also be applied to a situation where the water pressure varies slightly due to a wall resistance or any other factor. Therefore, the phrase “maintaining the water pressure” is also applicable to a water pressure that has varied by a matter of few percent. 
     As can be seen from the foregoing description, in the flush toilet  1  according to this embodiment, the backflow check structure  4  has a part exposed to the air but includes no driving mechanism such as a movable valve body. This reduces the chances of the flush toilet  1  according to this embodiment causing failures. 
     (2) Variations 
     Note that the embodiment described above is only an exemplary one of various embodiments of the present disclosure and should not be construed as limiting. Rather, the exemplary embodiment may be readily modified in various manners depending on a design choice or any other factor without departing from a true spirit and scope of the present disclosure. 
     Next, variations of the exemplary embodiment described above will be enumerated one after another. 
     (2.1) First Variation of Backflow Check Structure 
     A first variation of the backflow check structure  4   a  is illustrated in  FIGS. 4 to 6 . In the following description, any constituent element of this first variation, having the same function as a counterpart of the embodiment described above, will be designated by the same reference numeral as that counterpart&#39;s, and description thereof will be omitted herein. Note that the constituent elements, other than the ones to be described below, of the flush toilet  1  according to the first variation are the same as their counterparts of the flush toilet  1  according to the first embodiment described above. 
     The flush toilet  1  according to the first variation includes the backflow check structure  4   a  provided for the water supply path  3 , a water receiver  8 , and a drained water receiver  9  as shown in  FIG. 4 . In this variation, the drained water receiver  9  is provided in place of the base  26  according to the first embodiment (see  FIG. 1 ). 
     The backflow check structure  4   a  checks the backflow of the water running through the water supply path  3 . The backflow check structure  4   a  is provided for the water supply path  3 . Having the backflow of the water through the water supply path  3  checked by the backflow check structure  4   a  reduces, even if damage is done to a part of the water supply path  3 , the chances of the water that has run up in the bowl  23  (see  FIG. 1 ) flowing backward through the water supply path  3  as in the exemplary embodiment described above. In this first variation, the backflow check structure  4   a  includes a water outlet pipe  46   a , a water inlet pipe  42   a , a connecting pipe  47   a , a splash reducing portion  53 , and a pipe supporting portion  56  as shown in  FIG. 5 . 
     The water outlet pipe  46   a  is a pipe for discharging the water supplied from the water supply source toward the water inlet pipe  42   a . The water outlet pipe  46   a  has a water outlet port  461  at the downstream end face thereof. The water outlet port  461  is an opening through which the water running through the water outlet pipe  46   a  runs out. The water that has run out through the water outlet port  461  passes through the space, exposed to the air, inside the backflow check structure  4   a . In short, the water outlet port  461  lets the water that has been supplied from the water supply source run out toward the water inlet port  421 . In this variation, the water outlet pipe  46   a  is provided for the pipe supporting portion  56 . Also, in this variation, the center axis  462  of the water outlet pipe  46   a  is tilted with respect to the horizontal plane. 
     The pipe supporting portion  56  supports the water outlet pipe  46   a . In this variation, the pipe supporting portion  56  is provided for the splash reducing portion  53 , and is mounted to the water receiver  8  via the splash reducing portion  53 . Therefore, the pipe supporting portion  56  is fixed to the water receiver  8 . The pipe supporting portion  56  includes a standup plate  57  and a supporting plate  58 . 
     The standup plate  57  protrudes, in the direction aligned with the center axis  462  of the water outlet pipe  46   a , from the splash reducing portion  53  toward an upstream end. The standup plate  57  creates a gap between the splash reducing portion  53  and the water outlet port  461 . When viewed along the center axis  462  of the water outlet pipe  46   a , the standup plate  57  is formed in a U-shape. In this variation, the standup plate  57  has an opening  571  through its lowest surface. 
     The supporting plate  58  is a plate provided with the water outlet pipe  46   a , and is provided at the top of the standup plate  57 . In this variation, the supporting plate  58  is a flat plate that intersects at right angles with the center axis  462  of the water outlet pipe  46   a . The supporting plate  58  has a through hole, to which the water outlet pipe  46   a  is connected to communicate with the through hole. This makes, according to this variation, the lower surface of the supporting plate  58  level with the surface surrounding the opening of the water outlet port  461 . 
     The splash reducing portion  53  reduces, when the water running out through the water outlet port  461  enters the water inlet port  421 , the chances of the water splashing from the water inlet port  421  reaching the water outlet port  461 . If the water running inside the water inlet pipe  42   a  has a high pressure when the water running out through the water outlet port  461  enters the water inlet port  421 , then the water may flow backward from the water inlet port  421  or plash back from a pool of water on the water inlet port  421 , thereby splashing the water in some cases. Thus, according to this variation, the splash reducing portion  53  is provided to prevent the splashing water from reaching the water outlet port  461 . The splash reducing portion  53  is able to shut off the water that has splashed from the water inlet port  421 . In this variation, the splash reducing portion  53  includes a water shutoff plate  54  and a pending piece  55 . 
     The water shutoff plate  54  shuts off the water that has splashed from the water inlet port  421 . In this variation, the water shutoff plate  54  is a flat plate. According to the present disclosure, however, the water shutoff plate  54  does not have to be a flat plate. The water shutoff plate  54  includes at least one surface facing the water inlet port  421 . The one surface facing the water inlet port  421  is located at a certain distance, to say the least, from the water inlet port  421 . In this variation, the distance L from the one surface facing the water inlet port  421  to the water inlet port  421  suitably falls within the range from 15 mm to 30 mm, and more suitably falls within the range from 20 mm to 25 mm. 
     In this variation, the water shutoff plate  54  is perpendicular to the center axis  462  of the water outlet pipe  46   a , i.e., tilted with respect to the vertical axis. The water shutoff plate  54  is arranged between the water outlet port  461  and water inlet port  421 . The water shutoff plate  54  has a water passage port  541 . The water passage port  541  is located on the trajectory of the water running out through the water outlet port  461 . This allows the water running out through the water outlet port  461  to pass through the water passage port  541 . 
     In this variation, the diameter of the water passage port  541  is equal to or greater than the diameter of the water outlet port  461  and equal to or less than the diameter of the water inlet port  421 . Specifically, the diameter of the water passage port  541  is greater than the diameter of the water outlet port  461  by a predetermined dimension (e.g., about 2 mm in this variation). According to this variation, setting the diameter of the water passage port  541  at a value equal to or greater than the diameter of the water outlet port  461  facilitates the passage, through the water passage port  541 , of the water running out through the water outlet port  461 . On the other hand, setting the diameter of the water passage port  541  at a value equal to or less than the diameter of the water inlet port  421  reduces the chances of the water that has splashed from the water inlet port  421  entering the water passage port  541 . Furthermore, tilting the water shutoff plate  54  with respect to the vertical axis reduces the chances of the pool of the water formed on the water shutoff plate  54  remaining on the water shutoff plate  54 . 
     The pending piece  55  protrudes, in the direction aligned with the center axis  462  of the water outlet pipe  46   a  (i.e., along the trajectory of the water), from the outer periphery of the water shutoff plate  54  toward a downstream end. That is to say, in this variation, the pending piece  55  is perpendicular to the water shutoff plate  54 . 
     The water inlet pipe  42   a  receives the water running out through the water outlet port  461  and channels the water toward the bowl  23 . The water inlet pipe  42   a  has the water inlet port  421  at the upstream end face thereof. The water inlet port  421  communicates with the water discharge port  253  (see  FIG. 2 ), through which the water is discharged into the bowl  23 . In this variation, the center axis  422  of the water inlet pipe  42   a  is located on the extension of the center axis  462  of the water outlet pipe  46   a . In short, in this variation, the water inlet port  421  is also arranged on the trajectory of the water running out through the water outlet port  461  as in the embodiment described above. 
     The water inlet pipe  42   a  has an open end face around the water inlet port  421 . This open end face is parallel to the surface surrounding the opening of the water inlet port  421 . In other words, the open end face intersects at right angles with the center axis  422  of the water inlet pipe  42   a . The open end face is tilted with respect to the vertical axis. In this embodiment, the open end face is a tilted surface  424 . Any pool of water formed on the tilted surface  424  may flow along the tilted surface  424 . 
     In this variation, the tilted surface  424  is the end face of the water inlet pipe  42   a . According to the present disclosure, however, the tilted surface  424  may be formed, around the water inlet port  421 , as a surface broader than the end face of the water inlet pipe  42   a . In addition, according to the present disclosure, the tilted surface  424  may also be tilted with respect to the surface surrounding the opening of the water inlet port  421 . 
     The water inlet pipe  42   a  includes a diameter decreasing portion  423  at the upstream end thereof. The diameter decreasing portion  423  is a portion, of which the diameter decreases from the water inlet port  421  toward a downstream end. In this variation, the diameter decreasing portion  423  is formed in a tapered shape. The diameter decreasing portion  423  is formed, along the center axis  422  of the water inlet pipe  42   a , to cover a predetermined range from the water inlet port  421  toward the downstream end. The diameter decreasing portion  423  is formed at the upstream end of the water inlet pipe  42   a . In short, in this variation, the diameter decreasing portion  423  is provided for the water supply path  3 . 
     As described above, when the water runs out through the water outlet port  461  in a situation where the pressure of the water inside the water inlet pipe  42   a  has risen, the water may splash from the water inlet port  421  toward the water outlet port  461 . In this variation, however, providing the diameter decreasing portion  423  increases the chances of the water splashing while broadening its range along the taper. Thus, as the splashing water goes more distant from the water inlet port  421 , the water broadens its diameter and is more and more likely to splash away from the water outlet port  461 . This reduces the chances of the splashed water reaching the water outlet port  461 . Furthermore, according to this variation, the water shutoff plate  54  is provided between the water outlet port  461  and the water inlet port  421 , thus reducing the chances the splashed water passing through the water passage port  541  to reach the water outlet port  461 . 
     The connecting pipe  47   a  is a portion to which attached is a pipe such as tube that connects the water discharge portion  25  (see  FIG. 4 ) and the water inlet pipe  42   a  together. The connecting pipe  47   a  is mostly the same as the counterpart of the embodiment described above. In this variation, however, the connecting pipe  47   a  has an expanded portion  471 , which is a major difference from the embodiment described above. 
     The expanded portion  471  is a portion, of which the channel cross section expands toward a downstream end between the water inlet port  421  and the water discharge port  253 . In other words, the channel cross section of the expanded portion  471  is larger by a predetermined dimension than the channel cross section of a portion upstream of the expanded portion  471 . In this variation, the channel cross section is increased by providing a step  472 , of which the surface is perpendicular to the direction aligned with the channel. However, this is only an example and should not be construed as limiting. Alternatively, according to the present disclosure, the expanded portion  471  may also be formed in a tapered shape such that its channel cross section expands continuously toward a downstream end. 
     According to this variation, the expanded portion  471  provided for the water supply path  3  checks the back flow even when the pressure of the water inside the water inlet pipe  42   a  rises due to stagnation of the water flow, for example. In particular, according to this variation, the expanded portion  471  is formed as the step  472 , thus even more effectively checking the backflow at any point downstream of the expanded portion  471  inside the water supply path  3 . 
     The backflow check structure  4   a  with such a configuration is fixed to the water receiver  8 . As shown in  FIG. 4 , the water receiver  8  includes a peripheral wall  81  and a bottom wall  82 . In this variation, in a plan view, the backflow check structure  4   a  is surrounded with the peripheral wall  81  and is able to receive the water running along the splash reducing portion  53  and the water running on the end face (tilted surface  424 ) of the water inlet pipe  42   a . According to the present disclosure, however, the backflow check structure  4   a  does not have to be surrounded with the peripheral wall  81  or the bottom wall  82 , but only needs to receive the water running along the splash reducing portion  53  and the water running on the tilted surface  424 . As used herein, the phrase “in a plan view” means viewing some structure from over the upper surface thereof. 
     The peripheral wall  81  has an overflow opening  811 . The overflow opening  811  is able to keep the level of the water run up in the water receiver  8  a constant level or less. In this variation, the overflow opening  811  is implemented as a rectangular cutout (which may also be a square cutout). Alternatively, according to the present disclosure, the overflow opening  811  may also be a hole cut through a middle of the height of the peripheral wall  81 . That is to say, the overflow opening  811  does not have to be a cutout. 
     As shown in  FIG. 6 , the overflow opening  811  has a straight lower end  811   a , which is parallel to the horizontal plane. The lower end  811   a  of the overflow opening  811  is located below the lower end of the water inlet port  421 . Therefore, in this variation, the surface of the water run up in the water receiver  8  is located at a lower level than the water inlet port  421 , thus reducing the chances of the water flowing out of the water receiver  8  into the water inlet port  421 . 
     In this variation, the lower end  811   a  of the overflow opening  811  has a straight shape. According to the present disclosure, however, the lower end  811   a  may also have a V- or U-shape. 
     At least one drain (not shown) is connected to the water receiver  8 . The water running through the drain is supplied to the bowl  23 . The drain is formed by connecting a pipe such as a tube to a drainage fitting  83  connected to the water receiver  8  as shown in  FIG. 4 . The water that has leaked from the water inlet port  421  such as the water that has run along the tilted surface  424  of the water inlet pipe  42   a  or the water that has splashed from the water inlet port  421  flows into the water receiver  8 . In short, according to this variation, the drain may discharge the water that has run along the tilted surface  424  into the bowl  23 . 
     The drained water receiver  9  may receive the water running out through the overflow opening  811 . In this variation, the drained water receiver  9  is greater in dimensions than the water receiver  8  in a plan view. The outer peripheral edges of the drained water receiver  9  are standup edges, which may prevent the water received at the drained water receiver  9  from running out. In this variation, the water received at the drained water receiver  9  is channeled through the drain into the bowl  23 . According to the present disclosure, however, the water received at the drained water receiver  9  does not have to be channeled into the bowl  23  but may also be channeled toward the drain trap, the drainpipe, or the floor surface, for example. 
     (2.2) Second Variation of Backflow Check Structure 
     A second variation of the backflow check structure  4   b  is illustrated in  FIGS. 7 and 8 . In the following description, any constituent element of this second variation, having the same function as a counterpart of the embodiment described above, will be designated by the same reference numeral as that counterpart&#39;s, and description thereof will be omitted herein. Note that the constituent elements, other than the ones to be described below, of the flush toilet  1  according to the second variation are the same as their counterparts of the flush toilet  1  according to the first embodiment described above. 
     A flush toilet  1  according to the second variation includes the backflow check structure  4   b  provided for the water supply path  3  and a water receiver  8  as shown in  FIG. 7 . 
     The backflow check structure  4   b  checks the backflow of the water running through the water supply path  3 . The backflow check structure  4   b  is provided for the water supply path  3 . The backflow check structure  4   b  reduces, even if damage is done to a part of the water supply path  3  when the level of the water run up in the bowl  23  rises so much as to immerse the water discharge portion  25  in the water that has run up, the chances of the water run up in the bowl  23  (see  FIG. 1 ) flowing back through the water supply path  3 . In this second variation, the backflow check structure  4   b  includes, as shown in  FIG. 7 , a water outlet pipe  46   b , a water inlet pipe  42   b , the splash reducing portion  53  (see  FIG. 8 ), and a pipe supporting portion  56   b  (see  FIG. 8 ). 
     The water outlet pipe  46   b  is a pipe through which the water supplied from the water supply source is channeled toward the water inlet pipe  42   b  (i.e., a pipe through which the water runs out of the backflow check structure  4   b ) as shown in  FIG. 8 . The water outlet pipe  46   b  is a pipe through which the water enters the backflow check structure  4   b . The water outlet pipe  46   b  has a water outlet port  461  at the downstream end face thereof. The water outlet port  461  is an opening through which the water running through the water outlet pipe  46   b  runs out (i.e., the water supplied from the water supply source runs out toward the water inlet port  421 ). In this variation, the water outlet pipe  46   b  is attached to the bottom of the water receiver  8  via the pipe supporting portion  56   b . In this variation, the center axis  462   b  of the water outlet pipe  46   b  is aligned with the horizontal plane and intersects at right angles with the vertical line (vertical plane). The inner peripheral surface  463 , located at the end closer to the water outlet port  461 , of the water outlet pipe  46   b  is formed in a tapered shape such that the channel cross section thereof decreases toward the water outlet port  461 . This adequately increases the flow velocity of the water running out through the water outlet port  461 . 
     The water inlet pipe  42   b  receives the water running out through the water outlet port  461  and channels the water toward the bowl  23 . The water inlet pipe  42   b  has the water inlet port  421  at the upstream end face thereof. The water inlet port  421  communicates with the water discharge port  253  (see  FIG. 2 ) through which the water is discharged into the bowl  23 . The center axis  422   b  of the water inlet pipe  42   b  is aligned with the horizontal plane and located on the extension of the center axis  462   b  of the water outlet pipe  46   b . In short, in this variation, the water inlet port  421  is also located on the trajectory of the water running out through the water outlet port  461  as in the exemplary embodiment described above. The water inlet port  421  is tilted with respect to the center axis  422   b  of the water inlet pipe  42   b . The surface surrounding the opening of the water inlet port  421  is tilted with respect to the horizontal plane such that in the direction aligned with the trajectory of the water, the surface surrounding the opening of the water inlet port  421  is sloped downward toward the water outlet port  461 . This allows, even if the trajectory of the water running out through the water outlet port  461  draws a parabola, the water to be received effectively at the water inlet port  421 . 
     The splash reducing portion  53  reduces, when the water running out through the water outlet port  461  is going to enter the water inlet port  421 , the chances of splashed water reaching the water outlet port  461 . In this variation, the splash reducing portion  53  is arranged between the water outlet port  461  and the water inlet port  421 . Also, in this variation, the splash reducing portion  53  includes a first water shutoff plate  54   a  and a second water shutoff plate  54   b.    
     The first water shutoff plate  54   a  is a plate facing the water inlet port  421  to receive the water splashed from the water inlet port  421 . The first water shutoff plate  54   a  is aligned with the vertical plane and intersects (e.g., at right angles in this variation) with the center axes of the water inlet pipe  42   b  and the water outlet pipe  46   b . In this variation, the surface surrounding the opening of the water inlet port  421  is tilted with respect to the first water shutoff plate  54   a . The first water shutoff plate  54   a  has a first water passage port  541   a  (water passage port  541 ). The first water passage port  541   a  runs through the first water shutoff plate  54   a . In this variation, the diameter of the first water passage port  541   a  is equal to or greater than the diameter of the water outlet port  461  and equal to or less than the diameter of the water inlet port  421 . 
     The second water shutoff plate  54   b  is a plate facing the water outlet port  461  and the first water shutoff plate  54   a . The second water shutoff plate  54   b  is a plate for receiving the water that has run out through the water outlet port  461  and plashed back and splashed from the first water shutoff plate  54   a  and the water that has plashed back from the water inlet port  421  to pass through the first water passage port  541   a  of the first water shutoff plate  54   a . The second water shutoff plate  54   b  is aligned with the vertical plane and intersects (e.g., at right angles in this variation) with the center axis of the water inlet pipe  42   b  and the center axis  462   b  of the water outlet pipe  46   b . That is to say, in this variation, the second water shutoff plate  54   b  is parallel to the first water shutoff plate  54   a . The second water shutoff plate  54   b  has a second water passage port  541   b  (water passage port  541 ). The second water passage port  541   b  runs through the second water shutoff plate  54   b . In this variation, the diameter of the second water passage port  541   b  is equal to or greater than the diameter of the water outlet port  461  and equal to or less than the diameter of the water inlet port  421 . Even though the diameter of the second water passage port  541   b  is equal to the diameter of the first water passage port  541   a  according to this variation, the diameter of the second water passage port  541   b  may also be smaller or larger than the diameter of the first water passage port  541   a.    
     The water passage ports  541  (including the first water passage port  541   a  and the second water passage port  541   b ) are surrounded with a peripheral wall  542 . The peripheral wall  542  protrudes from at least a part of the circumference of the water passage ports  541  toward at least one of the water outlet port  461  or the water inlet port  421  in the direction aligned with the trajectory of the water. In this variation, the peripheral wall  542  for the first water passage port  541   a  protrudes from the entire circumference of the first water passage port  541   a  toward both the water outlet port  461  and the water inlet port  421  in the direction aligned with the trajectory of the water. Meanwhile, the peripheral wall  542  for the second water passage port  541   b  protrudes from the entire circumference of the second water passage port  541   b  toward the water outlet port  461  in the direction aligned with the trajectory of the water. 
     However, this is only an example and should not be construed as limiting. Alternatively, the peripheral wall for the first water passage port  541   a  may also protrude from the entire circumference of the first water passage port  541   a  toward only the water inlet port  421  in the direction aligned with the trajectory of the water or only the water outlet port  461  in the direction aligned with the trajectory of the water. Meanwhile, the peripheral wall  542  for the second water passage port  541   b  may protrude from the entire circumference of the second water passage port  541   b  toward the water inlet port  421  in the direction aligned with the trajectory of the water or both the water outlet port  461  and the water inlet port  421  in the direction aligned with the trajectory of the water. Optionally, the peripheral wall  542  may be formed on only a part of the circumference of the water passage ports  541  (including the first water passage port  541   a  and the second water passage port  541   b ). 
     With the peripheral wall  542  provided around the surface, facing toward the water inlet port  421 , of the first water passage port  541   a , even if the water that has run out through the water outlet port  461  plashes back and splashes from around the water inlet port  421  when entering the water inlet port  421  to spread along a cover wall  59  and the first water shutoff plate  54   a , the water will collide against the peripheral wall  542  to fall down. In addition, even if the water runs along the first water shutoff plate  54   a , the peripheral wall  542  prevents the water from entering the first water passage port  541 . This further reduces the chances of the water that has plashed back from around the water inlet port  421  passing through the first water passage port  541   a  to flow back toward the water outlet port  461 . 
     The backflow check structure  4   b  has the cover wall  59 . The cover wall  59  reduces the chances of the water running out through the water outlet port  461  bouncing back from the water inlet port  421  and the splash reducing portion  53  to splash toward the outside. As used herein, the “outside” refers to the outside of the backflow check structure  4   b  and may be inside of the outer parts  21  of the toilet body  2 . The cover wall  59  includes a first cover wall  591 , a second cover wall  592 , and a third cover wall  593 . 
     The first cover wall  591  connects the tip of the water outlet port  461  to the second water shutoff plate  54   b . The second cover wall  592  connects the second water shutoff plate  54   b  to the tip of the peripheral wall  542  for the first water passage port  541   a . The third cover wall  593  connects the first water shutoff plate  54   a  to the end of the water inlet pipe  42   b.    
     The water that has plashed back from the cover wall  59  or the splash reducing portion  53  is received at the water receiver  8 . At least one drain is connected to the water receiver  8 . The drain is formed by connecting a pipe such as a tube to a drainage fitting  83  connected to the water receiver  8 . The water running through the drain flows into the bowl  23  as in the first variation. Alternatively, the drain may also be connected to the drain trap  76  or the drainpipe  73 , for example. Still alternatively, the water running through the drain may be drained directly onto the floor surface. The water receiver  8  has a peripheral wall  81   a . As shown in  FIG. 7 , the backflow check structure  4   b  is arranged inside the peripheral wall  81   a  in a plan view. 
     The flush toilet  1  includes an overflow portion  91 , which is provided inside the water receiver  8  in a plan view. The overflow portion  91  has an overflow opening  811 . The overflow opening  811  is provided at a level slightly higher than the bottom of the water receiver  8  so as to drain the water that has run up in the water receiver  8  when the drainage capacity required is not satisfied by only the drain provided for the water receiver  8 . In this variation, the overflow portion  91  is formed to have a cylindrical shape and the opening at the top of the overflow portion  91  defines the overflow opening  811 . 
     The water that has entered the overflow opening  811  is discharged toward the floor surface. However, the water that has entered the overflow opening  811  does not have to be discharged toward the floor surface but may also be channeled toward the bowl  23 , the drain trap  76 , or the drainpipe  73 , for example. 
     (2.3) Other Variations 
     Next, other variations of the exemplary embodiment described above will be enumerated one after another. Note that the variations to be described below may be adopted in combination as appropriate. 
     In the exemplary embodiment and variations described above, the respective surfaces surrounding the respective openings of the water inlet port  421  and the water outlet port  461  are parallel to each other and have their respective centers aligned with each other. However, this is only an example and should not be construed as limiting. Alternatively, according to the present disclosure, when the water running out through the water outlet port  461  draws a parabola, for example, the water inlet port  421  may be located at any point on the parabola. 
     Furthermore, in the exemplary embodiment and variations described above, the center axis  462  of the water outlet pipe  46  and the center axis  422  of the water inlet pipe  42  are either perpendicular to, or tilted with respect to, the vertical line. However, their center axes  462  and  422  may be parallel to the vertical line. Also, in the exemplary embodiment and variations described above, the respective surfaces surrounding the respective openings of the water inlet port  421  and the water outlet port  461  are either parallel to, or tilted with respect to, the vertical line. According to the present disclosure, however, their surfaces may also intersect, at right angles, with the vertical line. In that case, even though the water splashed from the water reservoir  41  will enter the water inlet port  421  easily, the water may be introduced into the water inlet port  421  while curbing, as much as possible, the decline in the rush of the water running out through the water outlet port  461 . 
     Furthermore, the flush toilet  1  according to the embodiment described above is designed to be installed on the floor  75 . According to the present disclosure, however, the flush toilet  1  may also be a so-called “floating (or wall hung) toilet,” which is fixed to the rear wall  74  with a gap left between itself and the floor  75 . Still alternatively, the flush toilet  1  may also be a portable floor toilet, which is just put on the floor  75  without being fixed to the floor  75 . 
     The flush toilet  1  may or may not include private parts washing devices. Furthermore, the flush toilet  1  according to the exemplary embodiment described above is provided such that the water inlet port  421  is continuous with the bottom wall  45  of the water reservoir  41 . However, this is only an example and should not be construed as limiting. Alternatively, the flush toilet  1  may also be provided such that the water inlet port  421  (water inlet pipe  42 ) protrudes from the bottom wall  45  toward the water reservoir  41 . This will reduce the suction of the air along the bottom wall  45  into the water inlet pipe  42 , thus supplying water with more stability. 
     In the variations described above, the water running out through the overflow opening  811  is received at the drained water receiver  9 . According to the present disclosure, however, the drained water receiver  9  may be omitted. In that case, the water running out through the overflow opening  811  may be channeled along the drain, for example, toward the drain trap, the drainpipe, or the floor surface. 
     Furthermore, in the variations described above, a single drain is provided for the water receiver  8 . According to the present disclosure, however, a plurality of drains may be provided for the water receiver  8 . In short, at least one drain needs to be provided. 
     Furthermore, in the variations described above, the splash reducing portion  53  reduces the splash of the water from the water inlet port  421  using the water shutoff plate  54  in a plate shape. According to the present disclosure, however, the water shutoff plate  54  does not have to be used but a piece of cloth or a film, for example, may also be used. Furthermore, in the variations described above, the splash reducing portion  53  includes one or two water shutoff plates  54 . Alternatively, the splash reducing portion  53  may also include three or more water shutoff plates  54 . Piling a plurality of water shutoff plates  54  one upon another along the flow path further reduces the chances of the water splashed from the water inlet port  421  reaching the water outlet port  461 , which is beneficial. 
     Furthermore, in the variations described above, the water that has run along the tilted surface  424  is received at the water receiver  8  and then discharged through the drain. According to the present disclosure, however, the flush toilet  1  may also be configured to channel the water that has run along the tilted surface  424  directly into the drain. 
     (3) Aspects 
     A flush toilet ( 1 ) according to a first aspect includes: a bowl ( 23 ); at least one water discharge port ( 253 ) to discharge water into the bowl ( 23 ); a water supply path ( 3 ) to supply the water from a water supply source to the water discharge port ( 253 ) therethrough; and a backflow check structure ( 4 ,  4   a ,  4   b ) provided for the water supply path ( 3 ). The backflow check structure ( 4 ,  4   a ,  4   b ) checks a backflow of the water running through the water supply path ( 3 ). The backflow check structure ( 4 ,  4   a ,  4   b ) has: a water inlet port ( 421 ) exposed to the air and directly communicating with the water discharge port ( 253 ); and a water outlet port ( 461 ) to channel the water supplied from the water supply source toward the water inlet port ( 421 ). The water inlet port ( 421 ) is arranged on a trajectory of the water running out through the water outlet port ( 461 ). The water that has passed through the water inlet port ( 421 ) is channeled directly toward the water discharge port ( 253 ). 
     This aspect checks the backflow of the water running through the water supply path ( 3 ) because the water inlet port ( 421 ) is exposed to the air. In addition, the water running out through the water outlet port ( 461 ) is channeled directly into the water inlet port ( 421 ), thus applying water pressure to the water discharged through the water discharge port ( 253 ). The backflow check structure ( 4 ,  4   a ,  4   b ) has no driving mechanism such as a movable valve body, thus reducing the chances of causing failures. 
     In a flush toilet ( 1 ) according to a second aspect, which may be implemented in conjunction with the first aspect, the water supply path ( 3 ) has an expanded portion ( 471 ) between the water inlet port ( 421 ) and the water discharge port ( 253 ), and the expanded portion ( 471 ) has a larger channel cross section (by a predetermined dimension) than a portion, located upstream of the expanded portion ( 471 ), of the water supply path ( 3 ). 
     This aspect allows, even if a backflow is caused due to the water stagnating downstream of the expanded portion ( 471 ) along the water supply path ( 3 ) to build up the water pressure, the backflow to be still checked by the expanded portion ( 471 ). This reduces the splash of the water from the water inlet port ( 421 ). 
     In a flush toilet ( 1 ) according to a third aspect, which may be implemented in conjunction with the first or second aspect, the backflow check structure ( 4   a ,  4   b ) includes, between the water outlet port ( 461 ) and the water inlet port ( 421 ), at least one splash reducing portion ( 53 ) having a water passage port ( 541 ,  541   a ,  541   b ) to pass the water running out through the water outlet port ( 461 ). 
     This aspect allows, even if the water splashes from the water inlet port ( 421 ), the splash reducing portion ( 53 ) to reduce the chances of the splashed water reaching the water outlet port ( 461 ). 
     In a flush toilet ( 1 ) according to a fourth aspect, which may be implemented in conjunction with the third aspect, the water passage port ( 541 ,  541   a ,  541   b ) is formed to have a diameter that is equal to or greater than the water outlet port&#39;s ( 461 ) diameter and equal to or less than the water inlet port&#39;s ( 421 ) diameter. 
     According to this aspect, the water passage port ( 541 ,  541   a ,  541   b ) is formed to have a diameter equal to or greater than the diameter of the water outlet port ( 461 ), thus allowing the water running out through the water outlet port ( 461 ) to pass through the water passage port ( 541 ,  541   a ,  541   b ) easily. In addition, the water passage port ( 541 ,  541   a ,  541   b ) is formed to have a diameter equal to or smaller than the diameter of the water inlet port ( 421 ), thus reducing the chances of the water splashing from the water inlet port ( 421 ) entering the water passage port ( 541 ). 
     In a flush toilet ( 1 ) according to a fifth aspect, which may be implemented in conjunction with any one of the first to fourth aspects, the water supply path ( 3 ) includes a diameter decreasing portion ( 423 ) having its diameter decreasing from the water inlet port ( 421 ) toward a downstream end of the water supply path ( 3 ). 
     This aspect facilitates a tapered splash of the water from the water inlet port ( 421 ), thus reducing the chances of the splashed water reaching the water outlet port ( 461 ). 
     A flush toilet ( 1 ) according to a sixth aspect, which may be implemented in conjunction with any one of the first to fifth aspects, further has a tilted surface ( 424 ) formed around the water inlet port ( 421 ) and tilted with respect to a horizontal plane. 
     This aspect reduces, even if part of the water running out through the water outlet port ( 461 ) forms a pool around the water inlet port ( 421 ), the chances of the pool remaining around the water inlet port ( 421 ). This reduces the splash of the water even when the water running out through the water outlet port ( 461 ) agitates the pool of water formed around the water inlet port ( 421 ). 
     A flush toilet ( 1 ) according to a seventh aspect, which may be implemented in conjunction with any one of the first to sixth aspects, further includes a water receiver ( 8 ) to receive the water. At least part of the water receiver ( 8 ) is located below the water inlet port ( 421 ). 
     This aspect reduces the chances of the water that has failed to enter the water inlet port ( 421 ) overflowing to unintentional areas. 
     In a flush toilet ( 1 ) according to an eighth aspect, which may be implemented in conjunction with the seventh aspect, the water receiver ( 8 ) has an overflow opening ( 811 ). A lower end of the overflow opening ( 811 ) is located below a lower end ( 811   a ) of the water inlet port ( 421 ). 
     This aspect reduces, even if the water has run up in the water receiver ( 8 ), the chances of the water that has run up entering the water inlet port ( 421 ). 
     A flush toilet ( 1 ) according to a ninth aspect, which may be implemented in conjunction with the eighth aspect, further includes a drained water receiver ( 9 ) to receive the water running out through the overflow opening ( 811 ). 
     This aspect reduces the chances of the water running out through the overflow opening ( 811 ) overflowing to unintentional areas. 
     A flush toilet ( 1 ) according to a tenth aspect, which may be implemented in conjunction with any one of the seventh to ninth aspects, further includes at least one drain to discharge, into the bowl ( 23 ), the water that has run up in the water receiver ( 8 ). 
     This aspect allows the water that has failed to enter the water inlet port ( 421 ) to be channeled into the bowl ( 23 ) through a path different from the water supply path ( 3 ), which is beneficial from a hygienic point of view. 
     A flush toilet ( 1 ) according to an eleventh aspect, which may be implemented in conjunction with the third or fourth aspect, further includes a peripheral wall ( 542 ) protruding from at least a part of a surrounding portion, located around the water passage port ( 541 ,  541   a ,  541   b ), of the splash reducing portion ( 53 ) toward at least one of the water outlet port ( 461 ) or the water inlet port ( 421 ) in a direction aligned with the trajectory of the water. 
     This aspect reduces the chances of the water that has plashed back from around the water inlet port  421  passing through the first water passage port  541   a  to flow back toward the water outlet port  461 , among other things. 
     In a flush toilet ( 1 ) according to a twelfth aspect, which may be implemented in conjunction with any one of the first to eleventh aspects, a center axis ( 462 ,  462   a ) of a water outlet pipe ( 46 ,  46   a ,  46   b ) having the water outlet port ( 461 ) is tilted with respect to a vertical line. 
     This aspect reduces, even if the water that has flowed backward from the water inlet port ( 421 ) has splashed, the chances of the splashed water entering the water outlet port ( 461 ). 
     In a flush toilet ( 1 ) according to a thirteenth aspect, which may be implemented in conjunction with any one of the first to twelfth aspects, the diameter of the water outlet port ( 461 ) is equal to or less than the diameter of the water inlet port ( 421 ). 
     This aspect allows the water running out through the water outlet port ( 461 ) to enter the water inlet port ( 421 ) effectively. 
     In a flush toilet ( 1 ) according to a fourteenth aspect, which may be implemented in conjunction with any one of the first to thirteenth aspects, a center axis ( 422 ) of a water inlet pipe ( 42 ,  42   a ,  42   b ) having the water inlet port ( 421 ) is either tilted or perpendicular to a vertical line. 
     This aspect allows the water running out through the water outlet port ( 461 ) to enter the water inlet port ( 421 ) and then flow smoothly through pipes (e.g., the water inlet pipe ( 42 ) and the connection pipe ( 47 ) in the embodiment described above) communicating with the water inlet port ( 421 ). Thus, this aspect reduces the pressure loss to be caused before the water reaches the water discharge port ( 253 ). 
     A flush toilet ( 1 ) according to a fifteenth aspect, which may be implemented in conjunction with any one of the first to fifth and eleventh to fourteenth aspects, further includes a water reservoir ( 41 ) having an air opening ( 43 ) which is exposed to the air. The flush toilet ( 1 ) further includes a splash reducing jacket ( 48 ) configured to receive the water that has splashed from inside of the water reservoir ( 41 ) toward the air opening ( 43 ) and to let the received water channel toward the water reservoir ( 41 ). 
     This aspect allows, even if the water running out through the water outlet port ( 461 ) plashes back from the inner surface of the water reservoir ( 41 ) and splashes toward the air opening ( 43 ), the splashed water to be received at the splash reducing jacket ( 48 ), thus reducing the chances of the water leaking. 
     A flush toilet ( 1 ) according to a sixteenth aspect, which may be implemented in conjunction with any one of the first to fifth and eleventh to fifteenth aspects, further includes a water reservoir ( 41 ) having an air opening ( 43 ) which is exposed to the air. The water reservoir ( 41 ) has a water guide surface ( 451 ) sloping down toward the water inlet port ( 421 ). 
     This aspect allows the water that has run out through the water outlet port ( 461 ) but failed to enter the water inlet port ( 421 ) to be channeled along the water guide surface ( 451 ) toward the water inlet port ( 421 ), thus reducing the chances of the water stagnating. 
     A flush toilet ( 1 ) according to a seventeenth aspect, which may be implemented in conjunction with any one of the first to fifth and eleventh to sixteenth aspects, further includes a connecting member ( 6 ) communicating with the water supply path ( 3 ) and connected to the water supply source. The flush toilet ( 1 ) is configured such that the water that has passed through the connecting member ( 6 ) runs out through the water supply path ( 3 ) and then is directly channeled through the water outlet port ( 461 ). 
     This aspect allows the water to be supplied from the water discharge port ( 253 ) toward the bowl ( 23 ) by taking advantage of the pressure of the water in the water supply source, thus enabling the water to rush into the bowl ( 23 ). 
     The constituent elements according to the second to seventeenth aspects are not essential constituent elements for the flush toilet ( 1 ) but may be omitted as appropriate. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  Flush Toilet 
               23  Bowl 
               253  Water Discharge Port 
               3  Water Supply Path 
               4 ,  4   a ,  4   b  Backflow Check Structure 
               421  Water Inlet Port 
               423  Diameter Decreasing Portion 
               424  Tilted Surface 
               46 ,  46   a ,  46   b  Water Outlet Pipe 
               461  Water Outlet Port 
               471  Expanded Portion 
               53  Splash Reducing Portion 
               541 ,  541   a ,  541   b  Water Passage Port 
               542  Peripheral Wall 
               71  Water Supply Pipe (Water Supply Source) 
               8  Water Receiver 
               811  Overflow Opening 
               811   a  Lower End 
               9  Drained Water Receiver