referring more particularly to the drawings , fig1 shows a fragmentary portion of a typical evaporative cooler , which is indicated generally by the reference numeral 10 , to which is attached the automatic flushing and draining reservoir apparatus of the present invention , with that apparatus being indicated in its entirety by the reference numeral 12 . the evaporative cooler 10 , includes among other things , a floor pan 14 wettable cooler pads 15 , and a water distribution plumbing system or network 16 . since evaporative coolers are well - known in the art , it is not deemed necessary to completely illustrate such a structure and only a brief description of operation will be given to facilitate understanding of the reservoir apparatus of the present invention . typically , water under pressure is supplied to the plumbing system 16 which carries the water to the upper portion of the cooler &# 39 ; s cabinet and distributes it to the top of each of the cooler pads 15 . the cooler pads are thus wetted so that air being drawn into the cabinet through the pads by means of a suitable air handler such as a centrifugal blower , ( not shown ), will be cooled by evaporation . some of the water trickling down through the cooler pads 15 will , of course , evaporate and the remaining unevaporated water will drain into the floor pan 14 . in accordance with the present invention , the floor pan 14 of the evaporative cooler 10 is formed with an opening 18 so that the unevaporated water draining from the cooler pads 15 will pass through the opening 18 into the automatic draining and flushing reservoir apparatus 12 of the present invention . as will hereinafter be described in detail , the automatic flushing and draining reservoir apparatus 12 of the present invention , includes the major components of a tank 20 for containing water 22 that is used in operation of the cooler 10 , a pump 24 for supplying the water 22 to the cooler , a float controlled shutoff valve 26 for initially supplying the water 22 to the tank and periodically supplying makeup water thereto , and a siphon drain valve 28 which is employed for draining purposes . as seen in fig1 and 2 , the tank 20 is an upwardly opening structure having a bottom wall 30 with integral upstanding sidewalls 32 . the tank may be of any convenient configuration , such as the rectangular shape shown , and is mounted to the bottom of the floor pan 14 immediately below the opening 18 formed therethrough as will hereinafter be described in detail . with regard to size , the tank 20 is formed with a depth dimension sufficient to contain an amount of water 22 for proper operation of the cooler 10 , with that amount being determined by the size of the cooler , pumping capacity of the pump 24 , and the like . the area of tank 20 is to be as small as possible for reasons which will become apparent as this description progresses . a water supply line 34 passes through one of the sidewalls 32 of the tank 20 and has the float controlled shutoff valve 26 threadingly or otherwise attached to its outlet end . the opposite end ( not shown ) of the water supply pipeline 34 is connected to a suitable source of water under pressure such as a domestic water line . in this manner , the water 22 will be initially supplied to the tank 20 and thereafter will be periodically opened under control of the float 35 , to supply makeup water thereto and thus maintain the water level at a predetermined normal operating level 36 . the pump 24 may be of any suitable type which will pump the water 22 from the tank 20 through the pump outlet hose 38 to the water distribution plumbing network 16 of the evaporative cooler 10 . the siphon drain valve 28 as seen in fig4 includes a standpipe 40 that is mounted in a downwardly upset dimple or depression 42 formed in the bottom wall 30 of the tank 20 . the bottom end of the standpipe 40 passes through the bottom of the depression 42 and is provided with threads 43 by which a hose ( not shown ) or other disposal means may be connected thereto . a cylindrical cap 44 is coaxially demountably mounted on the standpipe 40 and is provided with internal webs 45 in the upper closed top portion thereof . the webs are designed to engage the upper end of the standpipe 40 for mounting purposes and to provide an open water passage zone 46 between the top of the standpipe 40 and the closed top end of the cap 44 , with the zone 46 being located above the normal water level 36 in the tank 20 . the cap 44 is provided with an elongated skirt portion which has a bottom edge 47 that is located within the depression 42 . locating the bottom edge 47 of the cap in the depression 42 , and locating the open zone 46 immediately above the normal operation water level 36 will herein after be described in detail . in normal operation of the evaporative cooler 10 , water under pressure is initially supplied to the tank 20 through the float control valve 26 to achieve the normal operating level 36 , and the float controlled valve will periodically open to supply makeup water to replace that lost by evaporation . the pump 24 will deliver the water 22 to the distribution plumbing network 16 of the cooler 10 , which wets the cooler pads 15 as hereinbefore described . the unevaporated water drainage from the pads 15 will return to the tank 20 through the opening 18 in the floor pan 14 of the cooler , and recirculation of the water will continue as long as no externally applied interrupting force is applied . the water 22 in the tank 20 will become increasingly contaminated with dirt and the concentration of minerals will increase during the above described normal operation of the cooler 10 , and periodic flushing and replacement of the water is desirable to prolong the life of the cooler . periodic flushing may be accomplished by simply shutting off the power to the pump 24 which allows the water in the cooler &# 39 ; s plumbing network 16 to drain back into the tank 20 , which in conjunction with the unevaporated water draining from the cooler pads 15 , will raise the water level in the tank 20 from its normal level 36 to a flooded level 50 which is shown in dotted lines in fig1 and 4 . when the water 22 reaches the flooded level 50 , the zone 46 will be underwater which results in priming of the siphon valve 28 . with the siphon valve 28 primed , the water 22 will be drained from the tank 20 . it will be noted that the size of the standpipe 40 is considerably larger in diameter than the water supply line 34 , therefore , the rate at which the tank 20 is drained is considerably faster than the incoming rate of fresh water supplied through the float controlled shutoff valve 26 . in this manner , a flushing action will take place and when the drainage is complete , the siphon valve 28 will lose its prime and fresh water will fill the tank 20 to the operating level 36 and normal operation of the evaporative cooler 10 may be resumed . the above described flushing and water replacement operation should be accomplished at periodic intervals during operation of the evaporative cooler 10 as hereinbefore mentioned . when operation of the cooler is to be terminated , such as at the end of a cooling season , or at other times of prolonged nonuse , shutting off of the power to the pump 24 and shutting off of the water supply to the tank 20 will completely drain the tank . complete drainage is desirable so that the cooler 10 will not contain a standing body of water during periods of nonuse . it will be noted that positioning of the bottom edge 47 of the cap 44 within the depression 42 formed in the bottom of the tank 20 , will cause complete drainage of the tank &# 39 ; s bottom and only a relatively small amount of water will remain within the depression 42 . in the preferred embodiment , the tank 20 includes an endless water collection trough 52 which is affixed , such as by welding , to the upper ends of the interior surfaces of the tank &# 39 ; s sidewalls 32 . the trough 52 is configured and sized so as to catch all of the unevaporated water that passes downwardly through the opening 18 in the floor pan 14 . as seen best in fig3 the trough 52 is provided with an aperture 54 in the bottom thereof and an overflow pipe 56 . the purpose of the trough 53 is to collect the returning uneavporated water and control the flow of that water into the bottom of the tank . the size of the aperture 54 is such that the outflow from the trough 52 will be slower than the rate of inflow thereto so that the trough 52 will fill to a level determined by the position of the top of the overflow pipe 56 , and a constant outflow from the trough 52 will take place during normal operation of the cooler 10 . during the above described flushing and / or complete draining operations , the constant outflow from the trough 52 will continue for a period of time after initiation of either of those operations . this feature insures that there will always be a sufficient amount of water to raise the level in the tank to the flooded level 50 upon initiation of either the flushing or the complete draining operations . in most evaporative coolers , the trough 52 will not be needed , however , in some instances , such as in coolers having relatively small water distribution plumbing networks , and in exceptionally dry regions where the evaporation rate is high , the troughs will insure proper operation of the reservoir device 12 of the present invention . mounting of the automatic flushing and draining reservoir apparatus 12 on the cooler 10 may be accomplished in a number of suitable manners , such as that shown in fig1 and 3 . in this preferred embodiment , a plurality of l - shaped brackets 60 are affixed to the endless trough 52 so as to extend upwardly therefrom toward the opening 18 formed in the cooler &# 39 ; s floor pan 14 . a plurality of fasteners 62 , such as the screws shown , are mounted in a planar cover member 64 and extend downwardly therefrom into threaded engagement with suitably tapped holes provided in the l - shaped brackets 60 . the cover 64 is configured to overlay the opening 18 provided in the floor pan 14 , and is somewhat larger than the opening . a plurality of spacers 66 are suitably affixed to the downwardly facing surface of the cover 64 adjacent the periphery thereof with those spacers being in resting engagement with the upwardly facing surface of the floor pan 14 . thus , the cover rests on top of the floor pan 14 in spaced relationship above the opening 18 , and the tank is suspendingly mounted from the cover 64 by means of the screws 62 and brackets 60 so as to be in bearing engagement with the bottom surface of the floor pan 14 . in addition to suspendingly mounting the tank 20 , the cover 64 serves to shield the interior of the evaporative cooler 10 , and its components , from direct exposure to the water 22 within the tank 20 , and this reduces the moisture content and mineral deposition within the cooler . it will be noted that the cover 64 is provided with an opening 68 formed therethrough , and the pump 24 extends upwardly from the tank 20 through that opening so that the motor of the pump is located within the cooler rather than within the tank 20 . this will isolate the pump &# 39 ; s motor as much as possible from the damaging effects of moisture and mineral deposition . it will be further noted that the pump 24 need not be located within the tank 20 at all , in that the same results could be obtained by mounting of a suitable pump ( not shown ) on the side of the tank , or at any other remote location , and supplying water thereto by suitable plumbing lines . the above described automatic flushing and draining reservoir apparatus 12 of the present invention is automatic only to the extent that it will automatically flush , or drain in response to the pump 24 being shut off and such will , in most instances , be accomplished manually . a fully automatic system can be employed such as those shown in fig6 and 7 and as will not be described in detail . in fig6 a suitable normally closed timing and delay device 70 is mounted in the power supply line 72 leading to the pump 24 , and at predetermined intervals , such as 24 hours , the timing and delay device 70 will open the power line 72 leading to the pump 24 . such interruption will start the flushing operation and the delaying function accomplished by the timing and delay mechanism 70 will continue such interruption for a sufficient length of time to allow the completion of the flushing operation . in fig7 a normally closed solonoid 76 is mounted in the power supply line 78 of the solonoid 76 and energization of the solonoid is controlled by a conductivity sensing mechanism 80 . when the water 22 in the tank is relatively fresh , i . e ., having a relatively low concentration of dissolved minerals , the water will act as an electrical insulator so that no current will flow between the probes 82 of the sensing mechanism 80 . when the concentration of minerals increases in the water , which will occur as hereinbefore described , to a point where the water is sufficiently conductive , current will flow between the probes and the solonoid 76 will be energized thus , interrupting power to the pump 24 . while the principles of the invention have now been made clear in illustrated embodiments , there will be immediately obvious to those skilled in the art , many modifications of structure , arrangements , proportions , the elements , materials , and components used in the practice of the invention , and otherwise , which are particularly adapted for specific environments and operation requirements without departing from those principles . the appended claims are therefore intended to cover and embrace any such modifications within the limits only of the true spirit and scope of the invention .