as shown in fig1 a standard sump 10 having a sump bottom 11 and a sump cover 12 is provided with a typical electric sump pump 14 ( which also may have a battery powered back up pump ) having a discharge line 15 to waste 16 . the sump pump 14 is line powered and / or batter powered may be actuated by any normal water level sensor such as , for example , by a float . as is well known , sump pump such as 14 experience failures either due to the loss of electric power , motor bum out or pump bearing failure . in the case of battery powered pumps , draw down of batter power my also lead to failure . in such situations , it is desirable to have a back up pumping system , and preferably one not subject to failure for the same reasons as pump 14 . my invention provides a water - powered sump pump generally indicated at 20 which includes a drive chamber 21 containing a power cylinder 22 which , as illustrated , is positioned preferably exterior of the sump and a pump chamber 24 which includes a pump cylinder 25 , located in the sump preferably adjacent to the bottom 11 . if desired , a support tube 30 may connect the drive chamber and pump chamber 21 and 24 to provide an overall housing assembly . the pump chamber 24 is illustrated as receiving a piston 31 which may be provided with seals such as an o - ring seal 32 and which is received in the cylinder 25 . a piston rod 33 attached the piston 31 extends through seals 35 into the pump chamber 24 and connects with a pumping piston 40 in the pump cylinder 25 . the piston rod 33 thus mechanically links the two pistons together . by use of a solid piston rod , one to one linear movement between pistons is achieved . it will be apparent that by substituting a lever linkage , that different relative movements could be obtained . the pump cylinder 25 is provided with inlets 50 and 51 which may be equipped with ball - check valves 52 . it would be appreciated that normally the inlet 50 will extend to adjacent the bottom of the sump as will the inlet 52 . the openings from the inlet to the interior of the pump chamber 25 are positioned on either side of the piston to provide a double acting positive displacement pump where one of the areas above , or below , the piston will be drawing sump water in while the other is discharging previously drawn in sump water upon reciprocal movement of the piston 40 . it will be appreciated that although i have shown a double acting piston / cylinder with two inlets , if desired , the pump could be constructed as a lift piston having a single inlet to the lower position of the chamber and a one - way valve opening through the piston to a single discharge from the upper portion of the pumping chamber or as a single stage , two cycle piston pump . the pump chamber as provided in the illustrated preferred embodiment is equipped with two discharge lines 54 and 55 provided with check valves 56 . the two discharge lines can communicate to a common discharge pipe 57 which discharges to waste 16 . the drive chamber 21 is similarly provided with two inlets 60 and 61 at positions on opposite sides of piston 31 . the inlets 60 and 61 are formed as a part of a reversing valve assembly 65 which will alternately supply pressurized fluid to either inlet 60 or 61 . such self - reversing valves are well known and may , if desired include pilot valves controlling movement of a main spool valve which controls the flow of fluid to the inlets 60 and 61 . such valves are common and are shown , for example , in u . s . pat . no . 5 , 931 , 395 , the teachings of which are herein incorporated by reference . in the embodiment illustrated in fig1 the reversing valve 65 utilizes inlets 60 and 61 as combination inlets / outlets so that as pressurized fluid is being provided to one side of the piston 31 , the other side of the piston is open through valve 65 to exhaust . of course , separate inlets and outlets may be substituted . the reversing valve 65 is provided with pressure water through a conduit 70 which in turn is connected to a source of pressure water such as the community potable water supply 71 . an outlet conduit 73 may be provided from the reversing valve 65 to waste 16 , in which case , in order to prevent contamination of the potable water supply , a back flow preventer 76 may be provided in conduit 70 or an air gap in conduit 77 . however , as illustrated in fig2 one advantage of separating the power cylinder 22 from the pumping cylinder or chamber 25 by a distance sufficient to raise the power cylinder above the maximum flood water level is that the discharge from the reversing valve 25 may be directly back into the sump . by providing an air gap between the reversing valve discharge and the maximum water level in the sump , back flow contamination is avoided . thus , as illustrated in fig2 the discharge 73 may extend back through cover 12 to the upper portion of the sump 10 where the sump top is above the maximum water level . where the top of the sump is below the maximum water level the discharge may be provided with an air gap above the sump . activation of the system can be by any desired water level sensor . i have illustrated a standard float valve 80 incorporating float 81 linked to operate valve 82 in the pressure water line . preferably float 81 will be positioned at a higher level in the sump than the level sensor for electric sump pump 14 whereby the water - powered sump pump system 20 will be activated only upon failure of the electric sump pump . alternatively , if desired , an electronically operated normally closed valve 83 may be provided connected to an electronic water level sensor . since the power necessary to open and maintain open such a valve can be nominal , long lived batteries may be employed for such as system . it will , of course , be appreciated that other valving assemblies , level sensors and conduit arrangements may be utilized as desired . further , where conditions may warrant , the driving housing 21 and pump housing 22 may be assembled together as a single unitary assembly to be positioned exterior of the sump with an intake conduit extending from the bottom of the pump to the inlets to the pumping chamber such that both the power chamber and the pumping chamber are positioned exterior of the sump . conversely they could both be positioned within the sump with the reversing valve positioned exterior of the sump . finally , it would be appreciated that the reversing valve similarly could be positioned interior of the sump and the outlet conduits for the reversing valve either ported direct to waste or open to the top of the sump above the maximum water level . by providing a self - acting reversing valve , operated by the pressure of the inlet water , the systems acts totally based upon water pressure to maintain the sump pump . if desired the reversing valve could be operated by a physical connection to piston 31 or to piston rod 33 , such that movement to adjacent top dead center or bottom dead center activates a linkage to a vale shifter . moreover , although i have shown both the driving assembly and the pumping assembly as employing pistons , it will be appreciated other positive placement pumps may be utilized . for example , in fig2 the pumping member is a diaphragm 85 . the power member in the power cylinder 22 could similarly be a diaphragm . importantly , as illustrated , the volume in the power cylinder 22 on each side of the piston or diaphragm is considerably less than the volume on either side of the piston or diaphragm in the pump cylinder 25 . this allows for conversion of the energy stored in the pressure water to a larger volume flow from the pump . for example , if the volumes in the power assembly are one - fourth the volume in the pumping assembly , approximately four times as much water can be pumped from the pumping assembly , at a correspondingly reduced pressure . this can provide for a relatively highly efficient pumping system while allowing the discharge from the power assembly to be ported directly to the sump to be pumped away as part of the gray water waste . it will be appreciated that , as used herein , the term volume is directed to the volume encompassed within the movement of the pistons . although i have shown my invention as embodied in a preferred embodiment shown in the drawings , it would be appreciated that others may wish to utilize my invention in different forms and use different component parts . those skilled in the art will readily recognize that the embodiment described herein represents merely one possible use of my invention .