How to Check the Valve for a Water Pump


Valves used in conjunction with water pumps serve a very important function. Whether they have flapper valve designs made from metal, rubber or plastic, or use ball bearings and seats, they both stop a surge or back flow of water when pressure lowers in the line, or the pump motor shuts off. Protective devices, check valves can keep contaminated water from backing up into a public water utility line, which insures that the water source remains safe and pure. Inspecting, repairing and replacing check valves requires only a few hand tools and easy steps.

Things You'll Need

  • Penetrating oil
  • Pipe wrenches
  • Drain pan
  • Large end wrenches
  • Carburetor cleaner
  • Wire brush
  • Rags
  • Work bench
  • Vice
  • Determine if your sump or water tank level has been rising with the pump in the "Off" position. Any unexplained water rise in the tank will indicate a bad check valve that allows a back-flow of water through the valve device and seat. Remove the filler neck on the tank and smell the contents of the tank. Mold, sewer-like or bitter odor indicate back-flow contamination.

  • Locate your check valve on your water pump line. It will be located on the line between the holding tank or sump and the water pump. Many check valves have brass construction, shaped like large T-fittings, while other check valves have plastic designs, with tubular or cylindrical shapes. Either type can be mounted-spliced into the line in a horizontal or vertical configuration. Look for external leaks at the valve line fittings or at the inspection cap. Wipe the valve down with carburetor cleaner and rag.

  • Shut off the main water supply to the pump and place a large drain pan under the valve. Depending upon the clamping devices, use a screwdriver to loosen the flexible hose clamps, or use an end wrench to loosen the metal or PVC plastic retainer nuts. Pull the hoses or lines off the valve, allowing residual water to drain in the pan. Take the valve to a work bench and place it in a vice.

  • Clamp the valve securely in a vice. Use an end wrench to unscrew the inspection cap, if so equipped. Examine the inside. If encrusted with debris and rust, use a wire brush and carburetor cleaner to cleanse the inside. If the valve contains a ball bearing, spring and retainer seat, test the spring action to make sure it has tensile strength and has no broken parts. Make sure the ball bearing seat has no rust or deterioration. The ball bearing must be smooth, with no burs or rust pits.

  • Check the flapper valve, if you have this design. Flapper valves can be make of rubber, polymer plastic, or metal, mounted on a hinge or fastened to a mount inside. Some have springs. Examine the flapper valve to see if it has closed in the non-pressure position. If it appears only slightly open, the valve flapper can not seal and will allow back-flow. Look at the valve seat for rust, deterioration or any particle obstructions. Rubber valves can crack and deform. If you see any of these symptoms, replace the entire valve assembly.

Tips & Warnings

  • You can clean and lubricate the inside of the valve with penetrating oil and replace the system if the valve only needed cleaning. Use new hose clamps to refasten the hoses to the valve. If made of PVC line, use plumber's thread tape to assemble the line lock nuts, as well as on the threads to the inspection cap. Do not forget to prime the hoses or lines with water via the inspection cap opening before you start the pump.

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  • Photo Credit plumbing image by Inger Anne Hulbækdal from
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