flows through conduit 32 filter 33 and conduit 36 to the sump 25 a check valve 34 in bypass conduit 35 allows flow around the filter when the filter is clogged or is otherwise unable to handle all of the flow in line 32 the above described operation requires that solenoid valve 37 whose operation is hereafter described be in the closed position opening of the solenoid valve 31 allows flow through the conduits 39 and 40 and through a second pressure relief valve 30 the second pressure relief valve 30 is set to open when the pressure in line 28 exceeds a second predetermined value which is lower than the first predetermined value so that the hose may be readily coiled on the reel as explained hereinafter typically the second predetermined value is in the order of 500 psi but may also be varied so long as the pressure is sufficient to hold the piston 21 in the position shown in fig2 with the tines 10 in the closed position accordingly when solenoid operated valves 31 and 37 are in their closed positions the pressure in lines 28 and 23 are at the higher pressure controlled by valve 29 but upon opening of solenoid operated valve 31 by moving same to position the passage 31a in communication with line 39 the pressure in lines 28 and 23 are reduced to the second predetermined pressure by reason of the pressure relief through the valve 30 the first predetermined pressure is set at a value sufficient.