Patent Publication Number: US-6658673-B2

Title: Toilet valve assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of PCT Application Serial No. PCT/US02/01824, filed on Jan. 18, 2002, and is a continuation of and claims priority from U.S. patent application Ser. No. 09/957,812, filed on Sep. 20, 2001 now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 09/765,690, filed on Jan. 19, 2001 is now U.S. Pat. No. 6,484,327, the disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a dual flush-volume valve assembly for a toilet tank. More particularly, the invention provides a modular dual flush-volume valve assembly for a toilet tank that may be installed as either, or converted between, a single flush-volume system and a double flush-volume system. 
     BACKGROUND OF THE INVENTION 
     In the past, most toilets manufactured in the U.S. discharged approximately 3-5 gallons of water per flush. More recently, however, concerns with water conservation, combined with federal law requiring new toilets to have a maximum discharge volume of 1.6 gallons per flush, have led to the development of new water-conserving toilet systems and various devices for reducing the water consumption of older toilets. 
     One example of a device used to increase the efficiency of older toilets is a dual flush-volume toilet tank outflow valve assembly. Dual flush valve assemblies utilize separate flush valves that discharge different amounts of water for flushing solid and liquid waste. In one type of dual flush-volume valve assembly, a high-volume flush valve is positioned near the bottom of the toilet tank to pass a higher volume of water for flushing solid waste, and a low-volume flush valve is positioned higher in the toilet tank for passing a lower volume of water for flushing liquid waste. Thus, a user may select a high-volume flush when clogging presents a problem, and otherwise use a low-volume flush. 
     While known dual flush-volume valve assemblies do offer improved water conservation relative to older, high-volume toilet systems, they also have several shortcomings. For example, known dual flush-volume valve assemblies permit little, if any, adjustment of the relative volumes of the low-volume flush and the high-volume flush. This can pose a problem in retrofitting older toilet tanks, as the volume of water passed from the toilet tank during a low-volume flush may be dependent upon the shape of the toilet tank. As an example, when using a dual valve assembly of a selected height, more water may be discharged by the low-volume valve from a taller tank than from a shorter tank, as the level of water in the shorter tank may be closer to the low-volume valve than in the taller tank. This may cause problems with flushing, as an inadequate amount of water to flush waste from the toilet bowl may be discharged if the maximum water level in the toilet tank is too close to the low-volume valve. 
     Furthermore, the conversion of a single flush-volume valve system to known dual flush-volume valve systems may pose various difficulties. These difficulties may cause many consumers to avoid converting a single-volume flush system to a dual flush system, even given the long-term cost advantages of using less water per flush. Likewise, some toilet tanks may not be suited for fitting with dual flush-volume valve systems, while others may not be suited for fitting with single flush-volume valve systems. For these reasons, manufacturers may have to manufacture, and stores may need to stock, both single-volume valve systems and double-volume valve systems, which may increase manufacturing and distribution expenses. 
     SUMMARY 
     Some embodiments provide a modular outflow valve assembly for a toilet tank, including a lower outflow tube section configured to be mounted to a toilet tank to pass water out of the toilet tank, wherein the lower outflow tube section has a high-volume flush valve configured to flush a first, higher volume of water when opened; an upper outflow tube section having a low-volume flush valve configured to flush a second, lower volume of water out of the toilet tank when opened, wherein the lower outflow tube section is configured to receive attachment of the upper outflow tube section to form a dual flush-volume configuration; and an overflow tube section, wherein the lower outflow tube section is configured to receive attachment of the overflow tube section in place of the upper outflow tube section to form a single flush-volume configuration. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view of a dual-volume configuration of a modular outflow valve assembly according to a first embodiment of the present invention positioned in a toilet tank, assembled in a dual flush-volume configuration. 
     FIG. 2 is a side elevational view of the embodiment of FIG. 1, with the low-volume flush valve in a first, lower position relative to the high-volume flush valve. 
     FIG. 3 is a side elevational view of the embodiment of FIG. 1, with the low-volume flush valve in a second, higher position relative to the high-volume flush valve. 
     FIG. 4 is a side elevational view of a second embodiment of an outflow valve assembly according to the present invention. 
     FIG. 5 is a side elevational view of a third embodiment of an outflow valve assembly according to the present invention. 
     FIG. 6 is a partially sectioned view of the embodiment of FIG. 5, with both valves in closed positions. 
     FIG. 7 is a partially sectioned view of the embodiment of FIG. 5, with the high-volume flush valve in an open position. 
     FIG. 8 is a partially sectioned view of the embodiment of FIG. 5, with the low-volume flush valve in an open position. 
     FIG. 9 is an exploded isometric view of a first embodiment of a flush mechanism suitable for use with an outflow valve assembly of the present invention. 
     FIG. 10 is an isometric view of the flush mechanism of FIG.  9 . 
     FIG. 11 is an isometric view of the flush mechanism of FIG. 9, illustrating the operation of the handle for a low-volume flush. 
     FIG. 12 is an isometric view of the flush mechanism of FIG. 9, illustrating the operation of the release button for a high-volume flush. 
     FIG. 13 is an isometric view of the flush mechanism of FIG. 9, illustrating the operation of the handle for a high-volume flush. 
     FIG. 14 is an exploded isometric view of a second embodiment of a flush mechanism suitable for use with an outflow valve assembly of the present invention. 
     FIG. 15 is an exploded isometric view of a third embodiment of a flush mechanism suitable for use with an outflow valve assembly of the present invention. 
     FIG. 16 is an exploded isometric view of a fourth embodiment of a flush mechanism suitable for use with the present invention. 
     FIG. 17 is an exploded isometric view of a fifth embodiment of a flush mechanism suitable for use with the present invention. 
     FIG. 18 is a partially-sectioned side view of a sixth embodiment of a flush mechanism suitable for use with the present invention. 
     FIG. 19 is a sectional view of the flush mechanism of FIG. 18, illustrating the operation of the flush mechanism for a low-volume flush. 
     FIG. 20 is a sectional view of the flush mechanism of FIG. 18, illustrating the operation of the flush mechanism for a high-volume flush. 
     FIG. 21 is an isometric view of an embodiment of an alternate handle mechanism suitable for use with an outflow valve assembly according to the present invention. 
     FIG. 22 is a side elevational view of a single-volume configuration of an embodiment of a modular outflow valve assembly according to the present invention. 
     FIG. 23 is a side elevational view of the embodiment of FIG. 1, assembled in a single flush-volume configuration. 
     FIG. 24 is a side elevational view of another embodiment of a modular toilet valve assembly according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS 
     Various embodiments of the present invention provide modular single or dual flush-volume toilet tank outflow valve assemblies that may be easily converted between single and dual flush-volume configurations. Furthermore, various embodiments of the dual flush-volume configurations offer improved adjustability and flush performance compared to known dual valve assemblies. 
     A first embodiment of a modular valve assembly according to the present invention is shown generally at  10  in FIG. 1, positioned in a toilet tank  12  and assembled in a dual flush-volume configuration. Modular valve assembly  10  includes a base  14  with which it may be mounted to the inside of toilet tank  12 . 
     A lower outflow tube section  16  extends upwardly from base  14 , and a high-volume flush valve  18  is positioned on the lower outflow tube section adjacent the bottom of the interior of toilet tank  12 . High-volume flush valve  18  is configured to empty essentially all water from toilet tank  12  when opened to provide a higher volume flush for flushing solid wastes. An upper outflow tube section  20  is slidably coupled to lower outflow tube section  16 , and a low-volume flush valve  22  is positioned on the upper outflow tube section. Low-volume flush valve  22  is configured to empty toilet tank  12  only partially, thus providing a water-saving, smaller volume flush. It will be appreciated that modular valve assembly  10  may be easily converted to a single-volume flush valve system by replacing upper outflow tube section  20  with an overflow tube section, as described in more detail below in reference to FIG.  22 . 
     The slidable connection of lower outflow tube section  16  to upper outflow tube section  20  allows the height of low-volume flush valve  22  to be adjusted relative to the height of high-volume flush valve  18 . This allows the volume of water discharged by low-volume flush valve  22  to be adjusted for toilet tanks of different sizes, permitting the volume of water discharged by the low-volume flush valve to be quickly and easily adjusted over a wide range of volumes. This wide range of adjustability allows valve system  10  to be used in essentially any new or existing gravity flush toilet system. Modular valve assembly  10  also includes an overflow tube section  24 , which also may be adjustable in height to provide infinitesimal control of the low-volume flush. As described in more detail below and depicted in FIG. 21, overflow tube section  24  may be connected directly to lower outflow tube section  16  to form a single flush-volume valve system with an adjustable overflow tube height if desired. 
     FIG. 1 also shows an example of a suitable setup for the operation of valve system  10  in a toilet. High-volume flush valve  18  and low-volume flush valve  22  are both attached to a single flush wand  26 , which is operated by a handle  28 . Low-volume flush valve  22  is connected to flush wand  26  with a first, shorter length of chain  30 , and high-volume flush valve  18  is connected to the flush wand with a second, longer length of chain  32 . Second length of chain  32  is configured to have more slack than first length of chain  30 . This allows low-volume flush valve  22  to be opened by pushing handle  28  only partially down when a low volume flush is desired, and both the low-volume flush valve and high-volume flush valve  18  to be opened by pushing handle  28  farther down when a higher volume flush is desired. In the depicted embodiment, handle  28  employs a special mechanism, described in more detail below, that prevents the handle from being pushed far enough to open high-volume flush valve  18  unless a handle release button  34  is held down. 
     FIGS. 2 and 3 show modular valve assembly  10  in more detail. As mentioned above, modular valve assembly  10  includes a base  14  configured to couple the moldular valve assembly  10  to the bottom  40  of toilet tank  12  and to pass water out of the toilet tank. In the depicted embodiment, base  14  takes the form of a spud, but it will be appreciated that base  14  may have any other suitable configuration. Base  14  includes a threaded portion  42  that fits through toilet tank outflow hole  43 , and is secured to bottom  40  of toilet tank  12  with a nut  44 . The connection may be sealed with a gasket  46 . 
     Lower outflow tube section  16  is connected to base  14 , and includes a hollow upright portion  48  to which upper outflow tube section  20  is coupled. Upright portion  48  supports upper outflow tube section  20  above base  14 , and also channels water discharged through low-volume flush valve  22  through toilet tank outflow hole  43 . Upright portion  48  may have any suitable configuration. For example, upright portion  48  may have a bend that offsets upper outflow tube section  20  relative to base  14 . In the depicted embodiment, however, upright portion  48  extends directly above base  14 , such that the hollow interior of upright portion  48  is positioned directly above and in line with the opening in base  14 . In this configuration, water discharged through low-volume flush valve  22  can pass straight down through lower outflow tube section  16  without any horizontal deflection, and thus may increase the continuous maximum water volume and velocity of the flush. 
     Lower outflow tube section  16  also includes a lower side tube  50  extending away from upright portion  48 , which connects high-volume flush valve  18  to upright portion  48 . Lower side tube  50  may have any suitable configuration, and may be positioned at any desired location on lower outflow tube section  16 . In the depicted embodiment, lower side tube  50  is oriented generally parallel to toilet tank bottom  40 , and is positioned directly adjacent the toilet tank bottom. This places the lower edge of the lip  52  of high-volume valve  18  very close to the bottom of toilet tank, and thus permits essentially all of the water to drain from the tank when the high-volume flush valve is opened. While high-volume flush valve is connected to upright portion  48  with lower side tube  50  in the depicted embodiment, it will be appreciated that high-volume flush valve may also be attached directly to the side of upright portion  48 , without the use of lower side tube  50 . 
     When water is discharged from toilet tank  12  via low-volume flush valve  22 , it is possible that some water may flow into lower side tube  50 . To direct water discharged through low-volume flush valve  22  away from the opening of lower side tube  50 , valve system  10  may include a water flow diverter disposed in the interior of lower outflow tube section  16 . This water flow diverter may have any suitable design. In the depicted embodiment, the water flow diverter takes the form of a plate  54  attached with a hinge to the joint between lower side tube  50  and upright portion  48 , within the hollow interior of lower outflow tube section  16 . In the absence of water flowing through lower side tube  50 , plate  54  hangs downward across the opening to lower side tube  50 , as shown in solid lines in FIG.  2 . When water is discharged through low-volume flush valve  22 , plate  54  blocks the opening of lower side tube  50 , and thus prevents water from flowing into the lower side tube. A stop is positioned in lower side tube  50  to prevent plate  54  from swinging into lower side tube  50  when water is flushed through low-volume flush valve  22 . 
     In contrast, when water is flushed through high-volume flush valve  18 , plate  54  is pushed away from the high-volume flush valve by the water, as shown in dashed lines in FIG.  2 . This allows the water to flow out of side tube  50  and out of toilet tank  12 . Alternatively, the water flow diverter may take the form of a stationary barrier  59  that extends partially over the opening of lower side tube  50 , as shown in FIG.  3 . 
     High-volume flush valve  18  is configured to cover the end of lower side tube  50  to control the discharge of water through the lower side tube. High-volume flush valve  18  is thus positioned at the free end of lower side tube  50 , and is pivotally anchored to a pair of arms  57  located on upright portion  48 . In the depicted embodiment, high-volume flush valve  18  is a flapper valve, but may also be any other suitable type of valve. High-volume flush valve  18  may include a seal extension  56  that extends past lower lip  52  of the high-volume flush valve when the high-volume flush valve is in the closed position, shown in solid lines in FIG.  2 . Seal extension  56  is configured to help prevent the opening of high-volume flush valve  18  by water flushed through low-volume flush valve  22  by increasing the total water pressure against the high-volume flush valve when the high-volume flush valve is closed. 
     As mentioned above, upper outflow tube section  20  is slidably coupled to upright portion  48  of lower outflow tube section  16 . This allows the height of low-volume flush valve  22  to be quickly and easily adjusted relative to the height of high-volume flush valve  18 . FIG. 2 shows low-volume flush valve  22  in a first, lower position relative to high-volume flush valve  18 , and FIG. 3 shows the low-volume flush valve in a second, higher position. Note that low-volume flush valve  22  is farther from the surface of the water in the toilet tank in FIG. 2, causing more water to flow out of the high-volume valve when it is opened. Another advantage of the use of a slidable joint is that the joint allows the height of low-volume flush valve to be chosen from a continuous range of possible heights. The portion of lower outflow tube section  16  that receives the upper outflow tube section  20  may be referred to as a connecting portion, and may be configured also to receive overflow tube  68  to form a single flush-volume configuration, as described in more detail below. 
     The construction of the slidable joint between lower outflow tube section  16  and upper outflow tube section  20  is shown in FIGS. 2 and 3. Upper outflow tube section  16  includes an elongate neck  58  configured to fit within upright portion  48  of lower outflow tube section  20  such that it may be slid into or out of the lower outflow tube section. Elongate neck  58  may have any desired length. Generally, a longer elongate neck  58  provides for a greater range of height adjustability for low-volume flush valve  22 . However, if elongate neck  58  has too great a length, it may interfere with the flow of water through lower side tube  50 . In the depicted embodiment, elongate neck  58  is long enough to just reach the top of lower side tube  50  when it is fully extended into lower outflow tube section  16 . The position of upper outflow tube section  20  relative to lower outflow tube section  16  may be fixed with a locking collar  60 . In the depicted embodiment, locking collar  60  is a worm-drive clamp, but upper outflow tube section  20  may be fixed to lower outflow tube section  16  with any other desired locking device. Furthermore, other suitable methods for fixing upper outflow tube section  16  in position relative to lower outflow tube section  20 , such as a friction mechanism using an O-ring seal, may also be used. 
     In addition to elongate neck  58 , upper outflow tube section also includes an upper side tube  62  and the aforementioned overflow tube  24 . Upper side tube  62  connects low-volume flush valve  22  to upright portion  48 , and provides a path for water to flow from low-volume flush valve  22  into elongate neck  58 . Upper side tube  62  may have any suitable configuration, and may be located in any desired position on upper outflow tube section  16 . In the depicted embodiment, lower side tube  62  extends diagonally upward from elongate neck  58 . Low-volume flush valve  22  is positioned at the upper end of upper side tube  62 , and is pivotally attached to a pair of arms  66  located on overflow tube  24 . In the depicted embodiment, low-volume flush valve  22  is a flapper valve, but it may also be any other suitable type of valve. 
     When upper outflow tube section  20  is raised or lowered relative to lower outflow tube section  16 , the height of overflow tube  24  also changes. To compensate for this, or to permit the maximum water level of the toilet to be adjusted, overflow tube  24  may have an adjustable height. In the depicted embodiment, overflow tube  24  has a slidable adjustment mechanism, although other mechanisms may be used. A sliding adjustment mechanism is preferable, as it allows the height of overflow tube  24  to be quickly adjusted to any desired height within a range of possible heights. In the depicted embodiment, overflow tube  24  is formed from an upper overflow tube section  68  that fits within a lower overflow tube section  70 . 
     Lower overflow tube section  70  of the depicted embodiment is integral with upper outflow tube section  20 , and may include a locking collar  72  for fixing the position of upper overflow tube section  68  relative to lower overflow tube section  70 . A toilet bowl refill tube  74  (or other suitable device) may be threaded into overflow tube  24  for refilling the toilet bowl after a flush, or may be placed elsewhere in the toilet tank. 
     Upper overflow tube section  68  may initially be provided with extra length to extend into lower outflow tube section  16 . This extra length may facilitate the conversion of modular valve system  10  between single flush-volume and dual flush-volume configurations, as it may allow for the use of a longer overflow tube in a single flush-volume configuration for taller, narrower toilet tanks. However, the extra length of upper overflow tube section  68  may also be cut off (or otherwise removed from) the upper overflow tube section, as indicated at  68 ′ in FIG. 3, where used in a dual flush-volume configuration. 
     Where a single-volume flush system is desired, upper overflow tube section  68  may be placed directly in lower outflow tube section  16 , without the use of upper outflow tube section  20 . This is depicted in FIG.  23 . In this configuration, the height of the top of upper overflow tube section  68  may be adjusted simply by sliding overflow tube into or out of lower outflow tube section  16 . Thus, in this manner, valve assembly  10  may be converted to a single flush-volume valve without the purchase of any additional parts. It will be appreciated that the outer diameter of upper overflow tube section  68  may be configured to be the same as the outer diameter of elongate neck  58  so that the upper outflow tube section  68  fits snugly within lower outflow tube section  16 . In this instance, lower overflow tube section  70  may have a may have a slightly larger diameter than elongate neck  58 . Alternatively, lower overflow tube section  70  may have substantially the same outer diameter as elongate neck  58 . In this configuration, upper outflow tube section  68  may have a slightly smaller outer diameter than elongate neck  58 , and may be secured in lower outflow tube  16  by tightening locking ring  60  sufficiently, or through the use of a suitable gasket (not shown). 
     A second embodiment of a modular valve assembly according to the present invention is shown generally at  110  in FIG.  4 . Modular valve assembly  110  is similar in appearance and operation to the first embodiment, but utilizes a different upper outflow tube section, indicated at  120 . Upper outflow tube section  120  has an offset overflow tube  124 , which allows low-volume flush valve  122  to be positioned directly over the base. In this configuration, water flushed through low-volume flush valve  122  passes directly downward from the low-volume flush valve out of the toilet tank, without any horizontal deflection. This may increase the continuous maximum water volume and velocity of the low-volume flush, and thus may lead to a more efficient flush. 
     Offset overflow tube  124  is formed from an upper overflow tube section  168  slidably coupled to a lower overflow tube section  170 . This allows the height of overflow tube  124  to be adjusted, and thus permits the overflow tube height to be changed to compensate for changes in the height of the low-volume flush valve, or to change the maximum water level in the toilet tank. A locking collar  172  may be provided to allow upper overflow tube section  168  to be fixed in position relative to lower overflow tube section  170 . A pair of arms  166  may be provided on overflow tube section  120  as a location for the attachment of low-volume flush valve  122 . A refill tube  174  for refilling the toilet bowl after a flush may be attached to upper overflow tube section  168 . 
     Positioning overflow tube  124  in an offset position also may allow the overflow tube to have a greater range of adjustability than if it were positioned directly over upper outflow tube section  120 . In the embodiment shown in FIG. 4, lower overflow tube section  170  extends below the upper edge  178  of upper outflow tube section  120 , permitting the length of upper overflow tube section  168  to be correspondingly increased for a greater range of adjustment. 
     As with the embodiment of FIGS. 1-3, valve assembly  110  may be converted to a single flush-volume valve configuration by removing upper outflow tube section  120 , and attaching an overflow tube assembly such as that shown at  1020  in FIG. 23, described in more detail below. Thus, a user may simply and easily convert valve assembly  110  to a single flush-volume configuration when desired. 
     FIGS. 5-8 show generally at  210  a third embodiment of a modular valve assembly according to present invention. Rather than a flapper-style valve system, modular valve assembly  210  provides a column-type valve assembly, in which an upright column structure  211  may be lifted directly upward along a guide  213  to open a space between the column structure and the valve base, thus allowing water to flow out of the toilet tank. As shown in FIGS. 5-6, valve assembly  210  includes a base  214  and the aforementioned column structure  211 , which is formed of a lower outflow tube section  216 , an upper outflow tube section  218 , a cap piece  220  and an overflow tube  222 . Upper outflow tube section  218  is adjustably coupled to lower outflow tube section  216  to allow the volume of the low-volume flush to be adjusted. Alternatively, cap piece  220  and overflow tube  222  may be used with alone base  214 , without lower outflow tube section  216  or upper outflow tube section  218 , to form a single flush-volume configuration of modular valve assembly  210 . 
     Base  214  is configured to couple modular valve assembly  210  to the bottom  40  of toilet tank  12  and to pass water out of the toilet tank. In the depicted embodiment, base  214  takes the form of a spud, but it will be appreciated that base  214  may have any other suitable configuration. Base  214  includes a threaded portion  230  that fits through toilet tank outflow hole  43 , and is secured to bottom  40  of toilet tank  12  with a nut  232 . The connection may be sealed with a gasket  234 . 
     Base  214  also includes an upper surface  236  that forms part of the high-volume flush valve. In the depicted embodiment, upper surface  236  is a flat surface configured to form a watertight seal with a gasket  238  situated on lower outflow tube section  216 . The high-volume flush valve is opened by separating gasket  238  from upper surface  236  of base  214 , permitting water to drain from toilet tank  12  through the base. The gasket and upper surface are separated by pulling upwardly on a ring  239  attached to upper outflow tube section  218 , thus lifting column structure  211  along guide  213 . 
     As described above, guide  213  extends upwardly from base  214  and guides the movement of column structure  211  when the lower outflow tube section is raised or lowered. Guide  213  may have any suitable configuration. In the depicted embodiment, guide  213  is formed from four upwardly-extending ribs  240  arranged in a cross-like configuration, but may have any other suitable configuration. Guide  213  may also include a series of holes or raised portions  241  to reduce the noise of water flowing down guide  213  as the toilet bowl is refilled after flushing. 
     Lower outflow tube section  216  includes a ring  242  that surrounds guide  213  to hold column structure  211  centered on guide  213 . Ring  242  is attached to the inside of lower outflow tube section  216  with one or more plastic spacers  244 , and travels along guide  213  as lower outflow tube section  216  is moved up or down to open or close the high-volume flush valve, respectively. Modular valve assembly  210  may have as many rings  242  as desired for guiding lower outflow tube section  216  (and upper outflow tube section  218 ) along guide  213 . Two rings  242  are shown in the depicted embodiment. 
     Lower outflow tube section  216  also includes a float  246 . Float  246  is formed from a hollowed, air-containing chamber surrounding lower outflow tube section  216 . When the high-volume valve is opened, float  246  holds the high-volume valve open until the water drains to the level of upper surface  236  of base  214 . One or more small holes  247  may be formed in the bottom of float  246  to allow for the equalization of pressure between the float and the outside atmosphere. Holes  247  open into the hollow interior of lower outflow tube section  216  so that any water that may get inside of float  246  will drain out of the toilet tank. 
     Similar in operation to the high-volume flush valve, the low-volume flush valve of modular valve assembly  210  is formed from the junction of upper outflow tube section  218  and cap section  220 . The seal of the low-volume flush valve is formed between the top surface  250  of upper outflow tube section  218  and a gasket  252  attached to the bottom of cap section  220 . Separating gasket  252  from top surface  250  lifts cap section  220  along guide  213 , and thus opens the high volume valve. A chain attachment ring  254  is disposed on cap section  220  to allow the attachment of a chain or wand so that cap section  220  may be lifted with wand  26 , or another suitable mechanism. A float  256  formed in cap section  220  holds the low-volume flush valve open until water drains to the level of top surface  250 . One or more small holes  257  may be provided to allow the pressure within float  256  to equalize with the outside atmosphere. 
     To allow the volume of the low-volume flush to be adjusted, upper outflow tube section  218  is adjustably coupled to the upper portion of lower outflow tube section  216 . Lower outflow tube section  216  and upper outflow tube section  218  may be adjustably coupled in any desired manner. For example, the upper portion of lower outflow tube section  216  and the lower portion of upper outflow tube section  218  may have complementary threads so that the height of the upper outflow tube section may be adjusted by turning the upper outflow tube section. In the depicted embodiment, however, upper outflow tube section  218  is slidably coupled to lower outflow tube section. A suitable locking device, such as a worm drive clamp  258 , may be used to fix upper outflow tube section  218  in position relative to lower outflow tube section  216 . 
     Overflow tube  222  is attached to the top portion of cap section  220 , and may have any suitable design for allowing excess water to drain from toilet tank  12 . For example, overflow tube  222  may have a fixed height relative to cap section  220 . In the depicted embodiment, however, overflow tube  222  has an adjustable height. This allows the height of the overflow tube to be adjusted to compensate for adjustments in the height of the low-volume flush valve, and also to allow the maximum water level in the toilet tank to be adjusted. 
     Overflow tube  222  is formed from a lower overflow tube section  260  slidably coupled to an upper overflow tube section  262 . Lower overflow tube section  260  of the depicted embodiment is formed from a molded tubular inner section of cap section  220 , but may also be formed from a separate tubular piece. Lower overflow tube section  260  preferably has a diameter that closely fits guide  213  so that guide  213  holds cap section  220  centered over upper outflow tube section  218  and lower outflow tube section  216 . Upper overflow tube section  262  fits snugly within, or outside of, the inner diameter of lower overflow tube section  260  so that it may be slid upward or downward relative to the lower overflow tube section to adjust the height of overflow tube  222 . A locking device, such as a worm drive clamp  266  (or any other suitable device), may be used to fix the height of upper overflow tube section  262  relative to lower overflow tube section  260 . 
     To prevent cap piece  220  from being moved above the top of guide  213 , guide  213  includes a stop  268  with a greater diameter than the diameter of upper overflow tube section  262 . Stop  268  may be attached to guide  213  in any suitable manner. In the depicted embodiment, cap  268  is connected to guide  213  with a threaded connection. 
     Stop  268  may include a refill hole  270  configured to accept a toilet bowl refill line. In the depicted embodiment, guide  213  also includes a refill tube  272  extending downwardly from refill hole  270  past the level of top surface  250  of upper outflow tube section  218 . This helps to prevent water flowing through refill hole  270  from compromising the integrity of the seal of the low-volume flush valve. 
     FIGS. 7 and 8 illustrate operation of the dual flush-volume configuration of modular valve assembly  210 . Referring to FIG. 7, when the entire column structure  211  is lifted from base  214 , water can flow through the high-volume flush valve formed by the gap between the lower outflow tube section and the base, thus emptying essentially the whole toilet tank. Next, referring to FIG. 8, when cap section  220  is lifted from upper outflow tube section  218 , water can flow through the low-volume flush valve formed by the gap between the upper outflow tube section and the cap section, thus only partially emptying the toilet tank. 
     Many types of flush mechanisms may be used to operate a toilet valve assembly according to the present invention. For example, a double handle system may be used, in which each outflow valve is operated by a separate handle. FIGS. 9-13 illustrate another suitable flush mechanism  310 , which utilizes a single handle  28  that operates both flush valves. Ordinarily, handle  28  opens only the low-volume flush valve. However, flush mechanism  310  includes a button  34  that may be depressed to allow operation of the high-volume flush valve with handle  28 . 
     The construction of flush mechanism  310  is shown in detail in FIG.  9 . Handle  28  attaches to the toilet tank with a cylindrical bushing  316  configured to extend through a hole in the toilet tank wall. One end  318  of bushing  316  is threaded so that bushing  316  can be attached to the toilet tank with a nut  321 . Nut  321  also holds a locking mechanism  320  in place, described in more detail below. 
     Handle  28  is fixed to one end of a hollow rotatable member  322  that extends through bushing  318 . A flush wand  26  is attached to the other end of hollow rotatable member  322  with a screw  325 , or other suitable fastener. Thus, pushing handle  28  downwardly causes flush wand  26  to rotate upwardly and pull open any valves connected to the flush wand. 
     As described earlier and shown in FIG. 1, flush wand  26  is connected to both the low-volume flush valve and the high-volume flush valve. Flush wand  26  is connected to the low-volume flush valve with a first, shorter connector  327 , and to the high-volume flush valve with a second, longer connector. Thus, when handle  28  is pushed, the low-volume flush valve is opened after a first, lesser amount of rotation of rotatable member  322 . The high-volume flush valve is opened only after rotatable member  322  travels through a second, greater amount of rotation. 
     To prevent handle  28  from rotating fully and opening the high-volume flush valve during ordinary use, flush mechanism  310  may include a high-volume flush control. The high-volume flush control typically has at least two possible states: a first state in which the opening of the high-volume flush valve is prevented, and a second state in which the opening of the high-volume flush valve is enabled. The first state will typically be the default state of the flush mechanism. Thus, a user&#39;s reflexive pushing of handle  28  will result in a low-volume flush. In contrast, the user generally must make a cognitive step in order to operate the high-volume flush. For example, in the depicted embodiment, the high-volume flush control prevents handle  28  from rotating far enough to open the high-volume flush valve unless button  34  is depressed while pushing on handle  28 . 
     The high-volume flush control includes a slidable member  326  extending through the interior of wand rotation tube  322 . Button  34  is disposed on one end of slidable member  326 , and a wand rotation stop  328  is disposed on the other end. When button  34  is not depressed, wand rotation stop  328  extends snugly over the top of flush wand  26 . This is the first state of the high-volume flush control of flush mechanism  310 . The top surface  330  of flush wand  26  is flat, causing wand rotation stop  328  to rotate when the flush wand is rotated. When button  34  is depressed, however, wand rotation stop  328  is pushed away from top surface  330  of flush wand  26 . Thus, slidable member  326  thus is not rotated with the wand. This is the second state of the high-volume flush control of flush mechanism  310 . A spring  332  may be disposed around wand rotation lock shaft  326  to bias wand rotation stop  328  into the first state by pushing against the outside of the toilet tank. 
     The rotational travel path of flush wand  26  is limited by two appendages on locking mechanism  320 . First, locking mechanism  320  has a wand rest support  334  that holds flush wand  26  in the rest position when handle  28  is not being operated. Second, locking mechanism  320  has a wand rotation stopping member  336 . Wand rotation stopping member  336  is configured to be a barrier to the rotation of flush wand  26  past the point at which the low-volume flush valve is opened, unless button  34  is depressed. As described above and illustrated in FIGS. 10-11, when button  34  is not depressed, wand rotation stop  328  turns with flush wand  26 . Thus, wand rotation stop  328  contacts wand rotation stopping member  336  after flush wand  26  has been rotated far enough to open the low-volume valve, and thus prevents the flush wand from being turned further. Wand rotation stopping member  336  may include an adjustment mechanism, typically a small screw  338 , to allow the exact stop position of flush wand  26  to be fine-adjusted. 
     In contrast, when button  34  is depressed, wand rotation stop  328  is disengaged from flush wand  26 , and does not turn with the wand. It thus does not contact wand rotation stopping member  336  as handle  28  is pushed, and does not stop rotation of flush wand  26 . This is shown in FIGS. 12-13. In this instance, flush wand  26  is free to turn far enough to open the high-volume flush valve and to thus allow the entire toilet tank to drain. Once the toilet tank has drained, flush wand  26  returns to its rest position against wand rest support  334 , and wand rotation stop  328  is moved back into position over flush wand  26  by spring  332 , readying the toilet for a low volume flush. 
     FIG. 14 illustrates a second embodiment of a flush mechanism suitable for use with a dual-flush valve assembly, generally at  410 . Flush mechanism  410  is similar to flush mechanism  310  in many aspects. For example, flush mechanism  410  includes a hollow rotatable member  412  that extends through a bushing  414  configured to be mounted to the toilet tank wall. A handle  416  is attached to one end of rotatable member  412 , and a first flush wand  418  is attached to the other end of rotatable member  412 . 
     Furthermore, flush mechanism  410  also has a high-volume flush control. The high-volume flush control includes a slidable member  420  that extends through the hollow interior of rotatable member  412 . A wand rotation stop  422  is attached to one end of slidable member  420 , and a button  424  may be attached to the other end of the slidable member. Button  424  may be pressed to move wand rotation stop  422  from its first state, positioned over first flush wand  418 , to its second state, in which it is not positioned over first flush wand  418 . For a more secure fit, slidable member  420  may include raised portions or flutings  425  to mate with complementary flutings  427  within button  424 . 
     Unlike flush mechanism  310 , however, flush mechanism  410  includes a second flush wand  426  to open the high-volume flush valve. Second flush wand  426  is mounted to an extension  428  of slidable member  420 , which may include flutings  430  to hold second flush wand  426  more securely. Second flush wand is lifted by a lifting member  432  disposed on first flush wand  418  that extends outwardly from the first flush wand. Thus, second flush wand is lifted when first flush wand is lifted by manipulation of handle  416 . Lifting member  432  of the depicted embodiment has an elongate, generally flat shape, but it will be appreciated that any other lifting member may be used without departing from the scope of the present invention. 
     Operation of flush mechanism  410  is similar to that of flush mechanism  310 . Depressing handle  416  when wand rotation stop  422  is in the first state causes the wand rotation stop  422  to contact a stopping member  438 , thus preventing the high-volume flush valve from being opened. However, when button  424  is depressed, moving wand rotation stop  422  into its second state, the wand rotation stop does not rotate with handle  416 , thus permitting the handle to be turned sufficiently far to open the high-volume flush valve. A spring  440  may be provided to bias button  424  outwardly, and thus to bias wand rotation stop  422  into the first state. Also, an elastic cord  434  may be attached between wand rest support  436  and either low-volume flush wand  418 , high-volume flush wand  426 , or both flush wands to bring the flush wands down to the rest position after a flush is completed. Furthermore, indicator symbols  442  may be molded into handle  416 , button  424 , and flush wands  418  and  426  to indicate which flush wands are controlled by the handle and button. 
     FIG. 15 depicts a third embodiment of a flush mechanism suitable for use with a dual-volume flush valve according to the present invention, generally at  510 . Flush mechanism  510  is similar to flush mechanisms  310  and  410  in many aspects. For example, flush mechanism  510  includes a hollow rotatable member  512  that extends through a bushing  514  configured to be mounted to the toilet tank wall. A handle  516  is attached to one end of rotatable member  514 , and a low-volume flush wand  518  is attached to the other end of rotatable member  514 . Flush mechanism  510  also has a high-volume flush control including a slidable member  520  that extends through the hollow interior of rotatable member  512 . A high-volume flush wand  528  is disposed on the end of slidable member  520 . 
     However, unlike flush mechanisms  310  and  410 , flush mechanism  510  includes a wand rotation engagement bracket  522  attached to a button  524  coupled to the end of slidable member  520 . Wand rotation engagement bracket  522  is configured to engage a complementary raised portion  526  on rotatable member  514  to cause slidable member  520  to turn with rotatable member  514  when button  524  is depressed and handle  516  is pushed. 
     As with the other embodiments described above, flush mechanism  510  has two states. In the first state, when button  524  is not pushed inwardly by a user, wand rotation bracket  522  does not engage raised portion  526  on rotatable member  514  when handle  516  is depressed. Thus, slidable member  520  is not turned with rotatable member  514 . However, in the second state, when button  524  is depressed, raised portion  526  engages wand rotation engagement bracket  522  when handle  516  is depressed. This causes slidable member  520  to turn with handle  516 , thus lifting high-volume flush wand  528  and causing the high-volume flush valve to be opened. A spring  530  may be included between button  524  and rotatable member  514  to bias wand rotation engagement bracket  522  into the first state. Also, an elastic cord  532  may be attached to high-volume flush wand  528  and another part of flush mechanism, such as a wand rest support  534 , to return the high-volume flush to its rest position once the flush is finished. 
     FIG. 16 shows, generally at  610 , another embodiment of a flush mechanism suitable for use with a valve assembly of the present invention. Valve assembly  610  has similarities to other embodiments described above. For example, flush mechanism  610  includes a hollow rotatable member  612  that extends through a bushing  614  configured to be mounted to the toilet tank wall. A handle  616  is attached to one end of rotatable member  612 , and a low-volume flush wand  618  is attached to the other end of rotatable member  612 . Also, a slidable member  620  extends through the hollow interior of rotatable member  612 . 
     However, the high-volume flush control of flush mechanism  610  operates differently from those of the embodiments described above. Wherein the high-volume flush controls of flush mechanisms  310 ,  410  and  510  are changed between states by pushing a button, flush mechanism  610  is changed between states by pulling slidable member  620  outwardly. The high-volume flush valve may then be opened by turning slidable member  620 . 
     To prevent the high-volume flush valve from being opened when in the first state, bushing  614  includes a flange  622  with a depression  624 . Depression  624  is configured to receive a complementary extension  626  disposed on an outer cap piece  628 , which is attached to the end of slidable member  620 . 
     The operation of flush mechanism  610  is as follows. Low-volume flush wand  618  may be opened simply by pushing on handle  616 . High-volume flush wand  630 , however, may not be opened simply by turning cap piece  628 . When in the first state, extension  626  is positioned within depression  624 , preventing cap piece  628  from being turned. Therefore, cap piece  628  must first be pulled outwardly, and then turned, to lift high-volume flush wand  630 . A spring  632  may be included to bias cap piece  628  into the first state, and elastic cords  634  and  636  may be included to pull high-volume flush wand  630  and low-volume flush wand  618 , respectively, to their rest positions after use. Also, handles may have a numerical (or other) code to depict visually the correspondence between a selected handle and its associated flush valve. In the depicted embodiment, handle  616  and wand  618  each include a number “1”, shown at  635  and  635 ′, respectively. Similarly, cap piece  628  and wand  630  each include a number “2”, shown at  637  and  637 ′, respectively. 
     A lifting member  640  for communicating motion between high volume flush wand  630  and low volume flush wand  618  may be provided if desired. In the depicted embodiment, lifting member  640  is fixed to low volume flush wand  618 , and extends over high volume flush wand  630 . When low volume flush wand  618  is lifted, lifting member  640  does not affect high volume flush wand  618 . However, when high volume flush wand  630  is lifted, the high volume flush wand  630  lifts lifting member  640 , which in turn lifts low volume flush wand  618 . This causes the low-volume flush valve to open whenever the high-volume flush valve is opened, and may help to decrease the amount of time necessary to empty the toilet tank. 
     Cap piece  628  may have any suitable shape. For example, cap piece  628  may have a flat configuration with a generally round circumference, or may have a shape like a traditional toilet handle. However, in the depicted embodiment, cap piece  628  includes a contoured extension  638  with a downwardly-curved perimeter configured generally to fit the shape of a finger of a user. In the depicted embodiment, contoured extension  638  is positioned such that a user pulls upwardly on the contoured extension to actuate a high-volume flush, and thus may be more awkward to use than handle  616 . This may make it less likely that a user will use the high-volume flush for situations in which it is not needed. However, it will be appreciated that contoured extension  638  may be placed in any other desired position on handle  616 . 
     FIG. 21 shows another example of suitable configurations for the handle and cap piece. Here, handle  916  and cap piece  928  have shapes that communicate to a user which valve is controlled by each part. For example, handle  916  may have the shape of the number “1” to show that the handle corresponds to low volume flush wand  918 , which may be labeled with a number “1”, as described above. Likewise, cap piece  928  may have the shape of the number “2” to show that the handle corresponds to high volume flush wand  928 , which may be labeled with a number “2”, as described above. 
     The handle  916  and cap piece  928  of FIG. 21 also may indicate which part is used to flush which type of waste. For example, liquid waste is often referred to as “number one” by many people, and especially children, while solid waste is often referred to as “number two.” Where handle  916  and cap piece  928  have the shapes shown in FIG. 21, a user, and especially a young user, may easily determine which part is to be used to flush which type of waste. This may allow a child to be trained at a young age to use the water-saving low volume flush to flush liquid wastes. 
     FIG. 17 illustrates generally at  710  another flush mechanism suitable for use with a valve system according to the present invention. Like the other flush mechanisms described above, flush mechanism  710  includes a hollow rotatable member  712  that extends through a bushing  714  configured be mounted to the toilet tank wall. A low-volume flush handle  716  is attached to one end of rotatable member  714 , and a low-volume flush wand  718  is attached to the other end of rotatable member  714 . 
     Flush mechanism  710  also includes an elongate member  720  extending through the hollow interior of rotatable member  714 . Unlike the corresponding piece in the prior embodiments, however, elongate member  714  is not slidable through the hollow interior of rotatable member  714 . Instead, elongate member  720  is independently rotatable. 
     A high-volume flush wand  722  is attached to one end of elongate member  720 , and a high-volume flush handle  724  is attached to the other end. High-volume flush handle  724  has a shape configured to be somewhat more awkward to use than low-volume flush handle  716 . Therefore, when a user reflexively operates flush mechanism  710 , the user will typically push on low-volume flush handle  716 . Likewise, when the user desires a high-volume flush, the user must cognitively decide to operate the somewhat more awkward high-volume flush handle  724 . This may be sufficient to prevent the user from flushing a full toilet tank of water in the absence of a decision that a high-volume flush is needed. 
     FIGS. 18-20 illustrate yet another flush mechanism suitable for use with the present invention, generally at  810 . Rather than employing a handle that operates a rotatable member to lift a flush wand, flush mechanism  810  employs a pullable member  812  that can be pulled a first, shorter distance to open low-volume flush valve  22 , or a second, greater distance to open high-volume flush valve  18 . Pullable member  812  extends through an opening in the top of toilet tank  12 , which may be fitted with a bushing  814 . Pullable member  812  of the depicted embodiment takes the form of an elongate, tubular form member, but have any other desired shape and construction. A handle  815  may be provided on pullable member  812  to facilitate use of flush mechanism  810 , and a collar  817  may be disposed about the perimeter of pullable member  812  to support pullable member  812  at a desired height relative to the top of toilet tank  12  while at rest. 
     Pullable member  812  is connected to low-volume flush valve  22  with a first, longer connector  816 , and to high-volume flush valve  18  with a second, shorter connector  818 . Thus, as pullable member  812  is pulled upwardly, shorter connector  818  opens low-volume flush valve  22  before longer connector  816  is able to open high-volume flush valve  18 . 
     To prevent the inadvertent opening of high-volume flush valve  18 , flush mechanism  810  also includes a high-volume flush control having a movable blocking member  820 . Blocking member  820  is configured to have both a blocking position, corresponding to a first state of the high-volume flush control, and a retracted position, corresponding to a second state of the high-volume flush control. The blocking position is configured to prevent pullable member  812  from being pulled sufficiently far to open high-volume flush valve  18  unless it is moved to the retracted position. 
     Blocking member  820  may have any suitable configuration. In the depicted embodiment, blocking member  820  takes the form of a lever mounted to the interior of pullable member  812  with a pivot  822 . Blocking member  820  is attached to pivot  822  at a location approximately midway between the ends of blocking member  820 , but may be attached at any other suitable point. 
     One end of blocking member  820  extends outwardly from the interior of pullable member  812  through a slot  824 , and the other end is coupled to one end of an actuating member  826 . Actuating member  826  is also coupled to a button  828  positioned at the top of pullable member  812 . Button  828  may be depressed by a user to move actuating member  826  downward, which in turn pushes on the end of blocking member  820 , causing the protruding end of blocking member  820  to pivot and retract through slot  824  into the interior of pullable member  812 . A biasing element such as a spring  829  may be included to bias blocking member  820  into the blocking position. 
     The operation of flush mechanism  810  is illustrated in FIGS. 19-20. Referring first to FIG. 19, when button  828  is not depressed, blocking member  820  extends outwardly from the interior of pullable member  812 . When pullable member  812  is pulled upwardly to flush the toilet, but blocking member  820  contacts the inside surface of the top of toilet tank  12  before the high-volume flush valve has been opened, preventing the pullable member from being pulled far enough to open the high-volume flush valve. 
     Referring next to FIG. 20, when button  828  is depressed, blocking member  820  is retracted into the interior of pullable member  812 . Thus, when pullable member  812  is pulled upwardly, blocking member  820  does not contact the inside surface of the top of toilet tank  12 , allowing the pullable member to be pulled far enough to open the high-volume flush valve. A stop  830  may be disposed at a desired location on pullable member  812  to prevent the pullable member from being pulled completely through the top of the toilet tank. Furthermore, an elastic cord  832  may be attached to pullable member  812  to return the pullable member to the rest position after use. 
     FIG. 22 shows generally at  1000  another exemplary single flush-volume configuration of a modular outflow valve assembly according to the present invention. Valve assembly  1000  includes a base  1002  configured to be attached to the bottom  1004  of a toilet tank. Valve assembly  1000  also includes a lower outflow tube section  1006 . Lower outflow tube section  1006  is similar to those shown above in the embodiments of FIGS. 1-3 and  4 . However, side tube  1008  includes a pair of arms  1010  coupled to an upright post  1012  to which a flush valve  1014  is connected. Side tube  1008  also includes a support  1016  to support the side tube against the bottom of the toilet tank. It will be appreciated, however, that the lower outflow tube sections of either of the embodiments of FIGS. 1-3 and  4  may be used in place of the depicted lower outflow tube section  1006 . 
     Lower outflow tube section  1006  also includes a generally upright portion  1018  configured to accept the insertion of an overflow tube assembly  1020 . Overflow tube assembly  1020  includes a lower overflow tube section  1022  configured to fit snugly within the inner diameter of upright portion  1018  of lower outflow tube section  1006 . The height of lower overflow tube section  1022  may be adjusted by sliding lower overflow tube section  1022  into out of lower outflow tube section  1006 , and may be fixed in a desired position via locking collar  1026 . 
     Overflow tube assembly  1020  also includes an upper overflow tube section  1028 . Upper overflow tube section  1028  is configured to fit within lower overflow tube section  1022 , and to be slidably adjustable with respect to the lower overflow tube section to provide an additional measure of adjustability for the height of the overflow tube assembly. In the depicted embodiment, upper overflow tube section  1028  is configured to fit snugly within a top portion of lower overflow tube section  1022 , and may be secured in a desired position with a locking collar  1030 . However, it will be appreciated that upper overflow tube section  1028  may have any suitable diameter, and may be secured in place via any suitable mechanism. 
     Valve assembly  1000  may be converted to a dual flush valve assembly simply by removing overflow tube assembly  1020  from lower outflow tube section  1006 , and replacing the overflow tube assembly with an upper outflow tube section having a low volume flush valve. Examples of suitable upper outflow tube sections include, but are not limited to, upper outflow tube sections  20  of FIG. 1 and 120 of FIG.  4 . Where upper outflow tube section  20  of FIG. 1 is used, overflow tube assembly  1020  may be inserted into the lower overflow tube section  70  of upper outflow tube section  20 . Thus, valve assembly  1000  allows a user to quickly and easily convert the valve between single flush-volume and double flush-volume configurations without having to purchase an entirely new valve assembly, and without having to detach the valve assembly from the bottom of a toilet tank. Furthermore, the embodiments disclosed herein allow a manufacturer to make individual parts that may be used in either single or dual flush-volume configurations. 
     FIG. 24 shows, generally at  1100 , yet another possible configuration of a modular valve system according to the present invention. Valve assembly  1100  is formed from a combination of a lower outflow tube section  1112  similar to that of the embodiment of FIGS. 22-23, and an upper outflow tube section  1114  and cap section  1116  similar to that of the embodiment of FIGS. 5-8. Valve assembly  1110  includes a high-volume flush valve  1118  positioned on lower outflow tube section  1112 , and a low-volume flush valve  1120  formed from the junction of upper outflow tube section  1114  and cap section  1116 . As with the previous embodiments, upper outflow tube section  1114  is slidably coupled to lower outflow tube section  1112  to allow the height of low-volume flush valve  1120  to be adjusted. 
     Valve assembly  1110  also includes a base  1122  configured to couple the valve assembly to the bottom of the toilet tank and to pass water out of the toilet tank. Furthermore, a guide  1117  extends upwardly from base  1122  to guide cap section  1116  when it is lifted to discharge water from the toilet tank. 
     Lower outflow tube section  1112  is similar in appearance and function to the lower outflow tube section of the embodiment of FIGS. 22-23. Lower outflow tube section  1112  is connected to base  1122 , and includes a hollow upright portion  1130  to which upper outflow tube section  1114  is coupled. Upright portion  1130  supports upper outflow tube section  1114  above base  1122 , and also channels water discharged through low-volume flush valve  1120 . It will be appreciated that numerous modifications, including the examples described above for the embodiment of FIGS. 1-3, may be made to lower outflow tube  1112  without departing from the scope of the present invention. 
     Lower outflow tube section  1112  also includes a side tube  1132  extending away from upright portion  1130 . Side tube  1132  connects high-volume flush valve  1118  to upright portion  1130 . As with the embodiment of FIGS. 1-3, side tube  1132  is oriented generally parallel to the toilet tank bottom, and is positioned directly adjacent the toilet tank bottom. This places the lower edge of high-volume flush valve  1118  close to the toilet tank bottom, allowing essentially the entire volume of water in the toilet tank to be flushed through high-volume flush valve  1118 . Instead of using side tube  1132 , high-volume flush valve  1118  may also be positioned directly on the side of upright portion  1130  without departing from the scope of the present invention. 
     In contrast to high-volume flush valve  1118 , low-volume flush valve  1120  is similar in appearance and function to the low volume flush valve of the embodiment of FIGS. 5-8. The seal of low-volume flush valve  1120  is formed between the top surface  1134  of upper outflow tube section  1114  and a gasket  1136  attached to the bottom of cap section  1116 . Separating gasket  1136  from top surface  1134  lifts cap section  1116  along guide  1117 , and thus opens low-volume flush valve  1120 . A float  1140  formed in cap section  1116  holds low-volume flush valve  1120  open until water drains to the level of top surface  1134 . 
     As with the embodiment of FIGS. 5-8, lower outflow tube section  1112  and upper outflow tube section  1114  may be adjustably coupled in any desired manner. In the depicted embodiment, upper outflow tube section  1114  is slidably coupled to lower outflow tube section  1112 . The outer diameter of upper outflow tube section  1114  is slightly smaller than the inner diameter of lower outflow tube section  1112 . Thus, upper outflow tube section  1114  fits within inner outflow tube section  1112  in a telescopic manner. A suitable locking device, such as a worm drive clamp, may be used to fix upper outflow tube section  1114  in position relative to lower outflow tube section  1112 . It will be appreciated that upper outflow tube section  1114  may also fit around the outside of lower outflow tube section  1112  without departing from the scope of the present invention. 
     To prevent water from overflowing the toilet tank, outflow valve assembly  1110  also has an overflow tube  1144 . The height of overflow tube  1144  may be configured to be adjustable so that it may be changed to compensate for changes in the height of the low-volume flush valve, and also to allow the maximum water level in the toilet tank to be adjusted. Overflow tube  1144  is formed from a lower overflow tube section  1146  slidably coupled to an upper overflow tube section  1148 . The outer diameter of upper overflow tube section  1148  is slightly smaller than the inner diameter of lower overflow tube section  1146 , and thus fits within the lower overflow tube section in a telescopic manner. A locking device, such as a worm drive clamp  1150 , may be used to fix the height of upper overflow tube section  1148  relative to lower overflow tube section  1146 . Alternatively, upper overflow tube section  1148  may also be configured to fit around the outside of lower overflow tube section  1146  in a telescopic manner. 
     Although the present disclosure includes specific embodiments, specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various elements, features, functions, and/or properties disclosed herein. The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.