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FIELD &amp; BACKGROUND 
       [0001]    The present invention relates to a method of priming a drainage apparatus for siphoning liquid, and a drainage apparatus. 
         [0002]    Due to global warming, changes in rainfall weather patterns have been seen in many parts of the world. Some regions experienced prolonged droughts, while others have had intense, sudden rainstorms which tend to cause flash floods. A flash flood can be defined as: “a flood that rises and falls quite rapidly with little or no advance warning, usually as a result of intense rainfall over a relatively small area”. Despite the proliferation of modern technologies, societies are still vulnerable to flash floods, especially so as more and more cities are becoming megacities and economies are increasingly nurtured by urbanization. Thus when flash floods occur, they can claim the lives of many people, as well as cause widespread damage to property and infrastructure, incurring economic losses. 
         [0003]    A conventional measure typically adopted to cope with flash flooding by building wider drainage canals has however not been effective due to the unpredictability of rainfall patterns brought about by global warming, in terms of the amount of rainfall forecasted to be deposited over a region. 
         [0004]    One object of the present invention is therefore to address at least one of the problems of the prior art and/or to provide a choice that is useful in the art. 
       SUMMARY 
       [0005]    According to a 1 st  aspect of the invention, there is provided a method of priming a drainage apparatus for siphoning liquid between first and second reservoirs. The apparatus includes a conduit arrangement having a first opening disposed in the first reservoir, a second opening disposed in the second reservoir and a liquid injection inlet arranged between the first and second openings, and at least one valve for controlling flow of the liquid along the conduit arrangement. The method comprises directing liquid into the conduit arrangement via the liquid injection inlet to fill up most of the conduit arrangement as controlled by the valve&#39;s configuration; directing liquid into the first reservoir to enable more liquid to enter into the conduit arrangement via the first opening and to flood the conduit arrangement to form a continuous liquid flow path which extends from the first opening up to at least the second opening, the continuous liquid flow path creating a siphon; and with the first opening kept below the liquid&#39;s surface level in the first reservoir, stopping the flow of liquid into the first reservoir to achieve a state of equilibrium of the siphon to prime the conduit arrangement. After the priming and in use, the siphon is triggered when more liquid is added into the first reservoir which causes the added liquid to be siphoned to the second reservoir via the primed conduit arrangement. 
         [0006]    It is to be appreciated that in the above context, the state of equilibrium is defined as the hydrostatic pressure at both ends of the continuous liquid flow path is in equilibrium and the siphon halts until it is triggered. 
         [0007]    Liquid is may include water (such as rainwater, drinking water, sea water, irrigation water etc) and oil etc. 
         [0008]    Advantages of the proposed method may include allowing the drainage apparatus to be used for transferring/diverting of liquid from a source reservoir to a destination reservoir by using the siphoning effect, without requiring pumps to be installed. As long as the conduits of the drainage apparatus are filled with the liquid, the siphoning effect works automatically to transfer/divert the fluid, when the fluid pressures in the two reservoirs are not equalized. This benefit means minimal human monitoring and maintenance are required for operating the drainage apparatus. 
         [0009]    The method of may include, prior to directing liquid into the first reservoir, further comprising releasing air trapped in the mostly filled conduit arrangement. The method may also include, prior to directing liquid into the conduit arrangement, further comprising configuring the at least one valve to enable the conduit arrangement to be mostly filled. 
         [0010]    The conduit arrangement may include a plurality of conduits arranged in fluid communication, or it may also include a single integral conduit. 
         [0011]    According to a 2 nd  aspect of the invention, there is provided a drainage apparatus for siphoning liquid between first and second reservoirs. The apparatus comprises a conduit arrangement having a first opening disposed in the first reservoir, a second opening disposed in the second reservoir and a liquid injection inlet arranged between the first and second openings for directing liquid into to fill up most of the conduit arrangement; and at least one valve for controlling flow of the liquid along the conduit arrangement; wherein prior to using the drainage apparatus for siphoning the liquid, the liquid injection inlet is configured to receive liquid to fill up most of the conduit arrangement as controlled by the valve&#39;s configuration; and wherein the first opening is configured to receive more liquid which has been directed into the first reservoir to flood the conduit arrangement to form a continuous liquid flow path which extends from the first opening up to at least the second opening, the continuous flow path configured to create a siphon which is at a state of equilibrium to prime the conduit arrangement when, the flow of liquid into the first reservoir is stopped and the first opening is kept below the liquid&#39;s surface level in the first reservoir; whereby after priming and in use, the siphon is triggered when more liquid is added into the first reservoir which causes the added liquid to be siphoned to the second reservoir via the primed conduit arrangement. 
         [0012]    According to a 3 rd  aspect of the invention, there is provided a drainage apparatus adapted to siphon liquid between first and second reservoirs. The apparatus comprises first and second openings; a conduit arrangement; and at least one valve arranged along the conduit arrangement to control flow of the liquid in the conduit arrangement via the first and second openings. The first and/or second opening is configured to be at least twice the diameter of the conduit arrangement. 
         [0013]    The first opening may be disposed in the first reservoir and arranged to face the floor of the first reservoir. The second opening may be disposed in the second reservoir and arranged to face the floor of the second reservoir. 
         [0014]    The second opening may be disposed in the second reservoir and arranged to face away from the floor of the second reservoir. 
         [0015]    There may be more than one valve and the valves include check valves and return valves. At least some of the valves may be configured to enable air trapped in the conduit arrangement to be released therefrom. 
         [0016]    The conduit arrangement may include a plurality of conduits arranged in fluid communication, or the conduit arrangement may include a single integral conduit. 
         [0017]    If the conduit arrangement has a plurality of conduits, the plurality of conduits may include first and second conduits respectively configured with the first and second openings, a portion of the first and second conduits being positioned at a same liquid level. The apparatus may further comprise a drainage conduit being arranged at the second reservoir. Preferably, the drainage conduit is disposed to be spaced apart from the outlet by approximately 300 mm. Other distances are possible, 200 mm, 400 mm, 500 mm etc. 
         [0018]    The apparatus may include the first and second reservoirs the first and second reservoirs, in particular when a contractor is engaged to construct the reservoirs as well as to install the drainage apparatus. 
         [0019]    Preferably, the second opening is configured to be at least three times, or four times the diameter of the conduit arrangement. 
         [0020]    The conduit arrangement may include a transverse portion extending between the first and second reservoirs, the transverse portion having a series of undulations arranged therealong. This traverse portion may extend to great lengths depending on how far apart the two reservoirs are. As an example, the traverse portion may have a length of at least 1000 metres. 
         [0021]    According to a 4 th  aspect of the invention, there is provided a flood control system comprising the drainage apparatus based on the 2 nd  or 3 rd  aspect of the invention. 
         [0022]    It should be apparent that features relating to one aspect of the invention may also be applicable to the other aspects of the invention. 
         [0023]    These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Embodiments of the invention are disclosed hereinafter with reference to the accompanying drawings, in which: 
           [0025]      FIG. 1  shows a schematic of a drainage apparatus, according to a first embodiment; 
           [0026]      FIG. 2  shows a flow diagram for a method of priming the drainage apparatus of  FIG. 1 ; 
           [0027]      FIG. 3  shows a schematic of the drainage apparatus of  FIG. 1 , subsequent to performance of the method shown in  FIG. 2 ; 
           [0028]      FIG. 4  shows a schematic of another drainage apparatus, according to a second embodiment; 
           [0029]      FIG. 5  shows a schematic of a further drainage apparatus, according to a third embodiment; 
           [0030]      FIG. 6  shows a schematic of yet another drainage apparatus, according to a fourth embodiment; 
           [0031]      FIG. 7  shows a schematic of an alternative drainage apparatus, according to a fifth embodiment; 
           [0032]      FIG. 8  shows a schematic of yet a further drainage apparatus, according to a sixth embodiment; and 
           [0033]      FIG. 9  shows a schematic of a drainage apparatus, according to a seventh embodiment. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0034]      FIG. 1  shows a schematic of a drainage apparatus  100  according to a first embodiment, which is adapted to siphon liquid between first and second reservoirs  102 ,  104 . Each of the first and second reservoirs has walls  102   a,    102   b,    104   a,    104   b,  and a floor  102   c,    104   c.  The floors  102   c,    104   c  of the first and second reservoirs  102 ,  104  are located on a same level. For clarity, the definition of the drainage apparatus  100  in this instance excludes the first and second reservoirs  102 ,  104 . Examples of the first and second reservoirs  102 ,  104  include wells, drains, canals or the like, while the liquid includes water. In this instance, the first reservoir  102  defines a source from which the liquid is to be siphoned, and the second reservoir  104  defines a destination to which the siphoned liquid is to be discharged. Also, the first reservoir  102  has an opening  1022  from which the liquid can be received and collected into the first reservoir  102  (e.g. rainwater falling into the first reservoir  102  through the opening  1022 ). The second reservoir  104  may be sheltered, and has a drainage pipe  1042  (configured with a return valve  1044 ) located through one of the walls  104   b  for draining away excess liquid discharged into the second reservoir  104  to prevent overflowing thereof. The drainage pipe  1042  is coupled to other reservoirs which are not shown in  FIG. 1  due to space constraints. It is to be appreciated that the drainage apparatus  100  may also be known as a “liquid transfusion and waterworks system”. In the first embodiment, the drainage apparatus  100  is included as part of a flood control/anti-flooding system (not shown), that can be deployed to address flooding of drains or canals during occurrence of flash floods. 
         [0035]    The drainage apparatus  100  includes a conduit arrangement, which comprises a plurality of conduits  106   a - e  arranged in fluid communication, and a plurality of valves  108 ,  110  arranged along in at least some of the conduits  106   a - e . In this embodiment, the conduits are PVC pipes although other suitable materials may be used depending on the applications, for example metallic pipes. Also, although a plurality of valves  108 , 110  are described, this may not be so as long as there is at least one valve. An example of the conduits  106   a - e  is water pipes. It is to be appreciated that the plurality of conduits  106   a - e  are detachably coupled to enable convenient assembly and disassembly, if required (e.g. facilitate easy transportation). Also, in this instance, the plurality of conduits  106   a - e  includes a set of first to fifth conduit members  106   a - e  (with substantially uniform diameters) whilst the plurality of valves  108 ,  110  includes a check valve  108  and a set of six return valves  110   a - f.  For description brevity, the first to fifth conduit members  106   a - e  will be referred to as first to fifth conduits  106   a - e  below. 
         [0036]    It is to be appreciated that the first conduit  106   a  includes an inlet  112  for the plurality of conduits  106   a - e  for siphoning the liquid, while the fifth conduit  106   e  includes an outlet  114  for the plurality of conduits  106   a - e  for discharging the siphoned liquid. The first conduit  106   a  is arranged to be positioned in the first reservoir  102 , and is of generally L-shaped. The first conduit  106   a  includes an L-shaped portion having a vertical arm  106   a   1  and a horizontal arm  106   a   2  which is coupled orthogonally to the vertical arm  106   a   1 . The vertical arm  106   a   1  of the L-shaped portion of the first conduit  106   a  rises above the walls  102   a,    102   b  of the first reservoir  102 , whilst an inverted U-shaped portion  103  extends from a free end of the horizontal arm  106   a   2  of the L-shaped portion of the first conduit  106   a.  The inverted U-shaped portion  103  is configured with the inlet  112  which acts as a liquid receiving point for the plurality of conduits  106   a - e . The inverted U-shaped portion  103  has a vertical part  103   a  which is orthogonal to the horizontal arm  106   a   2  and this is important to prime the drainage apparatus  100  as will be apparent later. The inlet  112  is arranged to face the floor  102   c  of the first reservoir  102 ; in other words, the inlet  112  is in an inverted configuration which prevents air from being introduced into the plurality of conduits  106   a - e  during siphoning which can detrimentally disrupt the siphoning action itself. Further, the inlet  112  is also about at least two times the diameter of the first conduit  106   a,  as shown in  FIG. 1  to reduce the possibility of air from entering first conduit  106   a.  It is also to be appreciated that the inlet  112  is located substantially near to the floor  102   c  of the first reservoir  102 . In addition, the inverted U-shaped portion  103  includes the check valve  108 , which permits flow liquid only in a direction from the inlet  112  to the outlet  114  of the plurality of conduits  106   a - e . A free end  106   a   12  of the vertical arm  106   a   1  of the L-shaped portion of the first conduit  106   a  is releasably closed with an air release cap  116 , which can be removed to enable any air trapped in the first conduit  106   a  (when filled with liquid) to be released. Also, the vertical arm  106   a   1  of the L-shaped portion of the first conduit  106   a  rising above the surrounding walls  102   a,    102   b  of the first reservoir  102  is fluid communicably coupled to the second conduit  106   b.    
         [0037]    The second conduit  106   b  is largely similar in structure to the first conduit  106   a,  except that the inverted U-shaped portion  103  is omitted. The second conduit  106   b  includes an L-shaped portion having a vertical arm  106   b   1  and a horizontal arm  106   b   2  which is coupled orthogonally to the vertical arm  106   b   1 . The horizontal and vertical arms  106   b   2 ,  106   b   1  of the L-shaped portion of the second conduit  106   b  are respectively configured with the first and second return valves  110   a,    110   b.  The horizontal arm  106   b   2  of the L-shaped portion of the second conduit  106   b  is coupled to the vertical arm  106   a   1  of the L-shaped portion of the first conduit  106   a.  Further, the second return valve  110   b  is arranged in the vertical arm  106   b   1  of the L-shaped portion of the second conduit  106   b  at a position above where the second conduit  106  is fluid communicably coupled to a first end  106   c   1  of the third conduit  106   c.  Similarly, a free end  106   b   12  of the vertical arm  106   b   1  of the L-shaped portion of the second conduit  106   b  is releasably closed with a liquid insertion cap  118 , which is removable for filling the plurality of conduits  106   a - e  with liquid. It is to be appreciated that the liquid insertion cap  118  is located proximal to the second return valve  110   b.    
         [0038]    The third conduit  106   c  is arranged transverse to the vertical arm  106   b   1  of the L-shaped portion of the second conduit  106   b,  and has a series of undulations along the length of the third conduit  106   c.  In particular, the third conduit  106   c  extends between the first and second reservoirs  102 ,  104 . It should be appreciated that the third conduit  106   c  may extend a greater distance, for instance from metres to kilometres (e.g. at least 1000 metres) depending on a distance apart between the first and second reservoirs  102 ,  104 . Also, substantially at the middle of the third conduit  106   c  is a rising vertical arm  106   c   2  configured with the third and fourth return valves  110   c,    110   d,  which are arranged spaced apart. Preferably, the rising vertical arm  106   c   2  is located at a highest point of the drainage apparatus  100 . The third return valve  110   c  is positioned above the fourth return valve  110   d.  The third return valve  110   c  is normally closed whereas the fourth return valve  110   d  is normally opened. During priming of the drainage apparatus which will be described below, these return valves  110   c , 110   d  enable air trapped within the conduits to be released. The vertical arm  106   c   2  may include a viewing window to check if there is air trapped below the third return valve  110   c  and if there is an air gap, the fourth return valve  110   d  is closed and the third return valve  110   c  is opened and liquid injected into the rising vertical arm  106   c   2  to displace the trapped air from the vertical arm  106   c   2 . Thereafter, the third return valve  110   c  is Closed and the fourth return valve  110   d  opened. 
         [0039]    A second end  106   c   3 , opposite to the first end  106   c   1 , of the third conduit  106   c  is fluid communicably coupled to the fourth conduit  106   d,  which is in turn coupled to the fifth conduit  106   e.  The manner in which the fourth conduit  106   d  is coupled to the fifth conduit  106   e  is a mirror arrangement of how the second conduit  106   b  is coupled to the first conduit  106   a,  and hence not repeated for brevity sake. It is to be appreciated that the fourth conduit  106   d  is structurally similar to the second conduit  106   b  (and has the fifth return valve  110   e ), except that a free end  106   d   12  of the vertical arm  106   d   1  of the fourth conduit  106   d  is coupled to the second end  106   c   3  of the third conduit  106   c.  Particularly, the fourth conduit  106   d  includes an L-shaped portion having a vertical arm  106   d   1  and a horizontal arm  106   d   2  which is coupled orthogonally to the vertical arm  106   d   1 . 
         [0040]    The fifth conduit  106   e  is arranged to be positioned in the second reservoir  104 , and is structurally similar to the first conduit  106   a,  except that the inverted U-shaped portion  103  is omitted, and replaced by an upward facing portion  106   e   3  and the fifth conduit  106   e  is also configured with the sixth return valve  110   f,  instead of the check valve  108 . The fifth conduit  106   e  includes an L-shaped portion having a vertical arm  106   e   1  and a horizontal arm  106   e   2  which is coupled orthogonally to the vertical arm  106   e   1 . The upward facing portion  106   e   3  is coupled orthogonal to the horizontal arm  106   e   2  and this angled arrangement is similar to the angled arrangement near the inlet  112  in the first reservoir  102  i.e. the arrangement between the vertical part  103   a  and the horizontal arm  106   a   2 . Both of these arrangements are configured to prime the drainage apparatus  100  i.e. to achieve a state of equilibrium for the liquid in the drainage apparatus  100 , as will be apparent later. The outlet  114  on the fifth conduit  106   e,  which acts as a liquid discharging point for the plurality of conduits  106   a - e , is configured to face opposite to and away from the floor  104   c  of the second reservoir  104 . Additionally, the outlet  114  is about at least two times the diameter of the fifth conduit  106   e  to prevent liquid from being sucked back into the fifth conduit  106   e  after being discharged therefrom, and to reduce the possibility of introducing air bubbles into the fifth conduit  106   e.  Further, the drainage pipe  1042  is disposed at least 300 mm above the outlet  114 . Like the inlet  112 , the outlet  114  is located substantially near to the floor  104   c  of the second reservoir  104 . It is also to be appreciated that the drainage pipe  1042  of the second reservoir  104  is positioned at a higher liquid level (in the second reservoir  104 ) than where the outlet  114  is positioned. It is further to be appreciated that the horizontal arm  106   a   2  of the L-shaped portion of the first conduit  106   a  and the horizontal arm  106   e   2  of the L-shaped portion of the fifth conduit  106   e  are respectively positioned in the first and second reservoirs  102 ,  104  at a same liquid level. 
         [0041]      FIG. 2  shows a flow diagram for a method  200  of deploying the drainage apparatus of  FIG. 1 . Water is used as an example of the liquid in the description of this method  200 . Prior to executing the method  200 , the first and second reservoirs  102 ,  104  are initially empty, and the plurality of conduits  106   a - e  is also empty. In addition, the six return valves  110   a - f  are initially configured as closed. 
         [0042]    The method  200  begins at step  202 , where the first, second and fifth return valves  110   a,    110   b,    110   e  are opened to enable water to be introduced into the plurality of conduits  106   a - e  through the free end  106   b   12  covered by the liquid insertion cap  118  to mostly fill the plurality of conduits  106   a - e  with the water. Thus, the liquid insertion cap  118  is to be removed for the plurality of conduits  106   a - e  to be filled. The liquid insertion cap  118  is screwed back once the plurality of conduits  106   a - e  is filled. This step  202  is also known as “priming”, as filling up the plurality of conduits  106   a - e  creates hydrostatic pressure therewithin to subsequently enable siphoning of the water from the first reservoir  102  to the second reservoir  104 . Once step  202  is completed, the air release caps  116  are removed to enable any air trapped (as bubbles) in the water, during filing the plurality of conduits  106   a - e , to be released, in a step  204 . Needless to say, the air release caps  116  are screwed back on once the trapped air bubbles are released. 
         [0043]    In a next step  206 , more water is introduced into the first reservoir  102 , which consequently provides sufficient fluid pressure to cause the water to flow into the inlet  112 , pass the check valve  108  and mix with the water filled in the plurality of conduits  106   a - e . In a further step  208 , the sixth return valve  110   f  is opened. Due to the continued provision of water (and thus increased fluid pressure) in the first reservoir  102 , the water is then caused to move through the plurality of conduits  106   a - e  and discharges via the outlet  114  into the second reservoir  104  by way of the siphoning action. That is, a continuous liquid flow path which extends from the inlet  112  to at least the outlet  114  is formed, and the continuous liquid flow path creates a siphon. The provision of the water at the first reservoir  102  is stopped when a level of the water collected in the first and second reservoirs  102 ,  104  equalizes, i.e. a state of equilibrium of the siphon is achieved as per step  210 , where the plurality of conduits  106   a - e  is then considered primed. It is to be appreciated that the state of equilibrium is defined as the hydrostatic pressure at both ends of the continuous liquid flow path is in equilibrium and the siphon halts until triggered. This state of equilibrium in the context of the schematic of the drainage apparatus  100  is depicted in  FIG. 3 . It is to be appreciated that the level  152  of the water in the first reservoir  102  covers and submerges the inlet  112 , while in the second reservoir  104 , the level  154  of water fills up at least to the brim of the outlet  114 . In other instances where a level of water in the second reservoir  104  however covers and submerges the outlet  114 , this level of the water collected is below the position of the drainage pipe  1042 , as will be appreciated. The drainage pipe  1042  is disposed at least 300 mm above the outlet  114 . Once the method  200  is executed, the drainage apparatus  100  is considered operational for the purpose of transferring/diverting any further excess water that subsequently collects in the first reservoir  102  to the second reservoir  104  to prevent overflowing or flooding at the first reservoir  102 . 
         [0044]    In use, the drainage apparatus  100  may be deployed as part of the flood control/anti-flooding system and the first reservoir  102  is located at a vicinity which is prone to flooding, whereas the second reservoir  104  is arranged at a distance (e.g. may be a few kilometres away) away from the first reservoir  102 . 
         [0045]    An example scenario for usage of the drainage apparatus  100  (after being deployed using the method  200 ) is briefly described here to illustrate its operation. When a heavy storm occurs, large amounts of rainfall water are collected in the first reservoir  102  and with the drainage apparatus  100  being already setup for operation, the large amounts of rainfall water are therefore diverted from the first reservoir  102  to the second reservoir  104  by being siphoned through the plurality of conduits  106   a - e . It is to be appreciated that the second reservoir  104  will not be filled because any excess rainfall water diverted to the second reservoir  104  is also drained away via the drainage pipe  1042  (to other reservoirs), once the water level in the second reservoir  104  rises to at where the drainage pipe  1042  is located. Once the storm has stopped, conditions in the first and second reservoirs  102 ,  104  then return to a state, whereby both water levels in the first and second reservoirs  102 ,  104  are substantially at the same level. So in this way, using the drainage apparatus beneficially prevents overflowing or flooding at the first reservoir  102 . 
         [0046]    Arranging the horizontal arm  106   a   2  of the L-shaped portion of the first conduit  106   a  and the horizontal arm  106   e   2  of the L-shaped portion of the fifth conduit  106   e  at the same liquid level has an advantage of creating a drainage apparatus which automatically starts the transfer of the liquid or stops the liquid transfer depending on the amount of water in the first reservoir  102 . When there is no water being channelled into the first reservoir  102 , the siphoning action will stop when the level of the water collected in the first and second reservoirs  102 ,  104  equalizes, i.e. a state of equilibrium of the siphon is achieved as per step  210  as explained above. In this way, this ensures that there is always liquid within the drainage apparatus to prime the drainage apparatus. When water starts to flow into the first reservoir again (for example, when rain starts to fall again), the siphon is triggered and the water transfer re-starts. 
         [0047]    If the horizontal arm  106   e   2  of the fifth conduit  106   e  is arranged lower than the horizontal arm  106   a   2  of the first conduit  106   a,  this water transfer would be continuous until the water in the drainage apparatus is drained out. In other words, if no water is being directed into the first reservoir, the siphoning action would continue to discharge the liquid within the drainage apparatus that is needed for the priming of the apparatus and this is not ideal as this will require the drainage apparatus to be primed again. 
         [0048]    Further embodiments of the invention will be described hereinafter. For sake of brevity, description of like elements, functionalities and operations that are common between the embodiments are not repeated; reference will instead be made to similar parts of the relevant embodiment(s). 
         [0049]    According to a second embodiment, there is proposed another drainage apparatus  300  shown in  FIG. 4 . The second and fourth conduits  106   b,    106   d  described in the first embodiment are omitted in this embodiment. Further differences between this drainage apparatus  300  and the drainage apparatus  100  of  FIG. 1  are as follow. It is also highlighted that components of the drainage apparatus  300  of  FIG. 4  similar to those in the drainage apparatus  100  of  FIG. 1  follow similar reference numerals, but with  3000  added as reference numeral. There are seven return valves  3110   a - f ,  302  in the drainage apparatus  300  of  FIG. 4 , and the positions of the first six return valves  3110   a - f  have been re-arranged compared to in the first embodiment. The first conduit  3106   a  further includes first and second return valves  3110   a,    3110   b  arranged in the vertical arm  3106   a   1  of the L-shaped portion of the first conduit  3106   a,  between the free end  3106   a   12  of the vertical, arm  3106   a   1  of the L-shaped portion and a point of the L-shaped portion where the first conduit  3106   a  is coupled to a connecting conduit  304 . Specifically, the connecting conduit  304  is a plain transverse member and does not include any return valves or the liquid insertion cap  3118 , and is coupled at one end  304   a  to the first conduit  3106   a,  and at an opposite end  304   b  to the third conduit  3106   c.  It is to be appreciated that the connecting conduit  304  is arranged to be positioned above the walls  102   a,    102   b  of the first reservoir  102 . As opposed to in the first embodiment, the third conduit  3106   c  is now arranged to be of generally U-shaped. Specifically, the third conduit  3106   c  includes a U-shaped portion having a left (vertical) arm  3106   c   1 , a right (vertical) arm  3106   c   2  and a horizontal arm  3106   c   3  which is coupled orthogonally to the left and right arms  3106   c   1 ,  3106   c   2  at their base. The liquid insertion cap  3118  is included at the left arm  3106   c   1  of the U-shaped portion of the third conduit  3106   c,  which is coupled to the connecting conduit  304 . The third return valve  3110   c  is arranged proximal to the liquid insertion cap  3118 . The right arm  3106   c   2  of the U-shaped portion of the third conduit  3106   c  is bent at a free end and coupled to the fifth conduit  3106   e;  and the bent portion of the right arm  3106   c   2  includes the fourth return valve  3110   d.  A horizontal arm  3106   c   3  of the U-shaped portion of the third conduit  3106   c,  connecting the left and right arms  3106   c   1 ,  3106   c   2 , is arranged to be positioned at a level below the floors  102   c,    104   c  of the first and second reservoirs  102 ,  104 . Further, it is to be appreciated that the bent portion of the right arm  3106   c   2  is located above the walls  104   a,    104   b  of the second reservoir  104 , similar to the connecting conduit  304 . The fifth conduit  3106   e  now includes the fifth and sixth return valves  3110   e,    3110   f  in the vertical arm  3106   e   1  of the L-shaped portion of the fifth conduit  3106   e,  while also including the seventh return valve  302  in the horizontal arm  3106   e   2  of the L-shaped portion of the fifth conduit  3106   e.  The fifth return valve  3110   e  is located above the sixth return valve  3110   f.    
         [0050]    According to a third embodiment, an alternative drainage apparatus  400  is proposed as per  FIG. 5 , which is largely similar to the drainage apparatus  300  of  FIG. 4 , but with minor differences. It is highlighted that like components of the drainage apparatus  400  of  FIG. 5  are similarly labelled as those of the drainage apparatus  300  of  FIG. 4 . In particular, for the third embodiment, the connecting conduit  304  couples to the first and third conduits  3106   a,    3106   c  at a much lower vertical position such that the connecting conduit  304  is now arranged to pass through the wall  102   b  of the first reservoir  102 . This is also similarly the case for the bent portion of the right arm  3106   c   2  of the U-shaped portion of the third conduit  3106   c,  which is now arranged to pass through the wall  104   a  of the second reservoir  104  to be coupled to the fifth conduit  3106   e.  In addition, unlike in  FIG. 4 , the fourth return valve  3110   d  is now arranged to be positioned in the horizontal arm  3106   a   2  of the L-shaped portion of the first conduit  3106   a.    
         [0051]    According to a fourth embodiment, yet a further variant drainage apparatus  500  is shown in  FIG. 6 , which is largely similar to the drainage apparatus  300  of  FIG. 4 , but with minor differences. So for referencing convenience, like components of the drainage apparatus  500  of  FIG. 5  are similarly labelled as those of the drainage apparatus  300  of  FIG. 3 . For the fourth embodiment, the horizontal arm  3106   c   3  of the U-shaped of the third conduit  3106   c,  connecting the left and right arms  3106   c   1 ,  3106   c   2 , is now arranged to be positioned at a level below the height of the walls  102   a,    102   b,    104   a,    104   b  of, but above the floors  102   c,    104   c  of the first and second reservoirs  102 ,  104 . In addition, the fifth conduit  3106   e  is now also configured with an inverted U-shaped portion  501  which extends from the free end of the horizontal arm  3106   e   2  of the L-shaped portion of the fifth conduit  3106   e,  similar to how the first conduit  106   a  is arranged in the first embodiment. Of course, this inverted U-shaped portion  501  is configured with the outlet  3114 . Further, the check valve  3108  is omitted and replaced by an eighth return valve  502 , which is arranged to be in the horizontal arm  3106   a   2  of the L-shaped portion of the first conduit  3106   a.  Also, this embodiment is configured such that liquid can be transferred/diverted from the first reservoir  102  to the second reservoir  104 , or vice versa, improving the versatility of the drainage apparatus  500  of this embodiment. It is to be appreciated that the drainage pipe  1042  of the second reservoir  104  is omitted during to the said improved capability of the drainage apparatus  500 . 
         [0052]    According to a fifth embodiment, another alternative drainage apparatus  600  is shown in  FIG. 7 , which is largely similar to the drainage apparatus  500  of  FIG. 6 , except that the inverted U-shaped portion  501  of the fifth conduit  3106   e  is now omitted, and the outlet  3114  is positioned in the same manner as described in the first embodiment. In addition, the eighth return valve  502  is omitted, and replaced with the check valve  3108 , similar to the arrangement in the first embodiment. 
         [0053]    According to a sixth embodiment, a variant drainage apparatus  700  is shown in  FIG. 8 , which is largely similar to the drainage apparatus  400  of  FIG. 5 . The only difference is that the horizontal arm  3106   c   3  of the U-shaped portion of the third conduit  3106   c  is now arranged to be positioned on a same level as both the connecting conduit  304  and the bent portion of the right arm  3106   c   2  of the. U-shaped portion of the third conduit  3106   c.  That is, the horizontal arm  3106   c   3  of the U-shaped portion of the third conduit  3106   c  (as in the third embodiment), the connecting conduit  304  and the bent portion of the right arm  3106   c   2  of the third conduit  3106   c  together forms a straight transverse member, which is labelled collectively in this sixth embodiment with reference numeral  702 . 
         [0054]    According to a seventh embodiment, a further drainage apparatus  800  is proposed and shown in  FIG. 9 , which is similar to the drainage apparatus  700  of  FIG. 8 , except that the outlet  3114  arrangement follows the configuration (using the inverted U-shaped portion  501 ) as described per the drainage apparatus  500  of  FIG. 6 . It is also to be appreciated that the drainage pipe  1042  of the second reservoir  104 , and the check valve  3108  are omitted in the seventh embodiment. The seventh embodiment is particularly configured such that liquid can be transferred/diverted from the first reservoir  102  to the second reservoir  104 , or vice versa. Thus the versatility of the said drainage apparatus  800  is improved. 
         [0055]    It is to be appreciated that the method  200  of  FIG. 2  is applicable to all of the second to seventh embodiments as described above. 
         [0056]    The proposed drainage apparatus  100 ,  300 - 800  discussed in afore embodiments advantageously enables transferring/diverting of liquid from a source reservoir to a destination reservoir by way of siphoning, without requiring usage of any pump or any moving part, thus saving costs. In addition, as long as the conduits of the drainage apparatus  100 ,  300 - 800  are filled with the liquid, the siphoning action will work to automatically divert the liquid, when the fluid pressure in the two reservoirs are not equalized. This means minimal human monitoring and maintenance are required for operation of the drainage apparatus  100 ,  300 - 800 . Therefore, the drainage apparatus  100 ,  300 - 800  beneficially helps to prevent overflowing and flooding at the source reservoir (which may be a monsoon drain for example). Further, the drainage apparatus  100 , 300 - 800  may be used to channel water from a water storage facility to a water treatment facility. 
         [0057]    The described embodiments should not however be construed as limitative. For example, the number of the return valves or check valves used is not limited as described above; any number of the return valves or check valves may be used, depending on the requirements of an application. This applies similarly to the number of conduits to be used, and is not limited to those described in the foregoing embodiments. Further the valves may be automatically (instead of manually) configured. In addition, the plurality of conduits  106   a - e  need not be of uniform diameters; each conduit may have a different diameter. Moreover, other suitable types of arrangements of the conduits are possible so long the siphoning effect is deployed and maintained to enable liquid transfer between the first and second reservoirs  102 ,  104 . Furthermore, the drainage apparatus  100 ,  300 - 800  may also include the first and second reservoirs  102 ,  104 . Additionally, the second reservoir  104  may be deeper than the first reservoir  102 . Also, the inlet  112  and outlet  114  may be arranged to be three times or four times the diameter of the conduit arrangement. The conduit arrangement may also be a single integral conduit, rather than a plurality of conduits  106   a - e . It has been found that the greater the depth of the first and second reservoirs  102 , 104 , the stronger is the siphoning action. Thus, the depth of the first and second reservoirs may be planned depending on the expected rate by which water needs to be transferred from the first reservoir to the second reservoir or vice versa. Although the embodiments described having a plurality of valves, which is preferred, but it should be mentioned that only one valve may be required. 
         [0058]    While the embodiments describe only two reservoirs but it should be appreciated that a number of reservoirs may be “cascaded” together to form a network of reservoirs with first reservoir transferring water to a second reservoir, and water is transferred from the second reservoir to a third reservoir and so on and so forth. 
         [0059]    Indeed, the flexibility of the drainage apparatus to be used in all sorts of imaginable terrain. For example, the embodiment of  FIG. 4 or 5  allows the pipe  316   c   3  to be buried underground or under water (such as beneath the ocean bed) to perform the water transfer. 
         [0060]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary, and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practising the claimed invention.

Summary:
A drainage apparatus ( 100, 300 - 800 ) for siphoning liquid between first and second reservoirs ( 102, 104 ) is disclosed. In a first embodiment, the apparatus ( 100 ) includes a conduit arrangement having a first opening ( 112 ) disposed in the first reservoir ( 102 ), a second opening ( 114 ) disposed in the second reservoir ( 104 ) and a liquid injection inlet ( 106 M 2 ) arranged between the first and second openings ( 112,114 ), and a plurality of valves ( 108, 110 ) for controlling flow of the liquid along the conduit arrangement. A method ( 200 ) for priming the drainage apparatus ( 100 ) comprises directing liquid into the conduit arrangement at ( 202 ) via the liquid injection inlet ( 106 M 2 ) to fill up most of the conduit arrangement as controlled by the valves&#39; configuration; directing liquid into the first reservoir ( 102 ) to enable more liquid to enter into the conduit arrangement via the first opening ( 112 ) to flood the conduit arrangement to form a continuous liquid flow path which extends from the first opening ( 112 ) up to at least the second opening ( 114 ), the continuous liquid flow path creating a siphon; and with the first opening ( 112 ) kept below the liquid&#39;s surface level in the first reservoir ( 102 ), stopping the flow of liquid into the first reservoir ( 102 ) to achieve a state of equilibrium of the siphon to prime the conduit arrangement. After the priming and in use, the siphon is triggered when more liquid is added into the first reservoir ( 102 ) which causes the added liquid to be siphoned to the second reservoir ( 104 ) via the primed conduit arrangement.