piston guide 65 in conjunction with the o ring 75 and the tapered portion 140 of the valve body 45 helps to create a funnel to minimize turbulent flow from the valve 50 as the valve seats on the tapered portion 140 of the housing 45 thereby minimizing water hammer similarly the tapered portion 225 and the rounded portion 220 of the broach body 70 collectively and individually smooth flow around the piston body also minimizing the effects of water hammer in the valve additionally the neck portion 200 of the broach body 70 allows inlet pressure to be more equally distributed therearound thereby centering the valve more efficiently thereby easing translation of the valve in the piston cap 55 and extending valve life referring now to fig1 5 and 5 a the anti backflow cartridge 30 is shown the cartridge has a tubular housing 250 that slips into the discharge tube 35 the tubular housing has a lip 255 that prevents the housing from slipping down into the discharge tube thereby giving a user easy access to the cartridge if maintenance is required a pair of anti backflow check valves 260 manufactured by neoperl are arranged in series in the tubular housing and each are held therein the tubular housing 250 the anti backflow valves provide enough resistance to minimize backflow while allowing enough flow to maximize the use of the toilet or urinal the o rings 265 also prevent fluid from flowing around each anti backflow check valve back to the valve assembly 10 a flange 280 may depend inwardly at a bottom of said tubular housing 250 in an alternative embodiment shown in fig1 the cartridge 250 is the discharge tube and if the cartridge needs replacement the discharge tube is replaced therewith the discharge tube 35.