The short answer
Tools and Materials
Before you start, gather the necessary tools and materials. You will need a hacksaw or PVC pipe cutter, PVC primer and cement, hose clamps, and a check valve sized to match your discharge pipe. Most sump pumps use 1.5-inch or 2-inch PVC pipe, so measure the outside diameter to select the right valve.
Having a bucket and some rags nearby helps manage any water that remains in the pipe. You may also want a small level to ensure the valve sits straight. If your discharge line has a union fitting, you can install the check valve on a removable section, which makes future cleaning much simpler.
- Hacksaw or PVC cutter
- PVC primer and cement
- Hose clamps or PVC glue
- Check valve with arrow
- Measuring tape and marker
- Bucket and rags
Locate the Right Spot
The check valve should sit as close to the pump as possible, but always below the floor level to avoid freezing. Look for a straight section of the discharge pipe where you can make two cuts. The valve must be accessible for inspection and cleaning, so avoid placing it inside a wall or tight crawlspace.
Keep the valve location written down, as spring storms can bring heavy rain that makes your sump pump work hard. A clear path to the valve helps you check it quickly after big weather events. Mark the pipe with a marker where you plan to cut.
Cut and Dry Fit
Turn off the sump pump and unplug it before cutting. Use the hacksaw to make two square cuts in the discharge pipe, removing a section roughly the length of the check valve plus a little extra for the fittings. Clean the cut edges with a file or sandpaper to remove burrs.
Dry fit the valve and any coupling pieces to confirm everything aligns. The arrow on the valve must point in the direction of water flow, which is away from the pump and toward the discharge outlet. If the valve has a flapper, check that it swings freely and seats properly.
Glue and Clamp
Apply PVC primer to the outside of the pipe ends and the inside of the valve sockets. Then apply PVC cement to both surfaces and push the valve onto the pipe with a slight twisting motion. Hold it in place for about 30 seconds to allow the cement to set. If you use rubber couplings with clamps, simply slide them over the pipe ends and tighten the clamps securely.
For a threaded valve, wrap plumber's tape around the male threads before screwing it on. Make sure the valve is oriented so the arrow points correctly, then hand-tighten and use a wrench for a snug fit. Double-check that all connections are secure before restoring power to the pump.
Test Your Work
After the glue or clamps are secure, plug the pump back in and pour a small amount of water into the sump pit to trigger the float switch. Watch the pump cycle on and off. The check valve should prevent water from flowing backward when the pump shuts off, keeping the discharge pipe full but not allowing backflow.
Listen for any rattling or water hammer, which can indicate the valve is not seated properly. If you notice any leaks, turn off the pump and tighten clamps or reapply cement. A properly installed check valve extends the life of your pump and reduces wear from frequent cycling.
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Call Now (817) 799-6732Frequently asked questions
Should I use a swing check valve or a spring check valve?
For sump pumps, a spring-loaded check valve is the right choice. It closes quickly and prevents water from slamming back, reducing water hammer. Swing valves are slower and can allow backflow if the pump cycles frequently. Choose a valve with a clear arrow and a removable cap for cleaning.
How do I know if my check valve is installed backwards?
Look for the arrow on the valve body. It must point in the direction the water flows, which is from the pump to the discharge pipe. If the arrow points toward the pump, water will not flow out, and the pump may run but move little water. Test by pouring water into the sump and watching the pump discharge.
Can I install a check valve without cutting the pipe?
Some check valves are designed to fit into an existing pipe using flexible rubber couplings, which require cutting but allow easy removal. There are also inline valves that slip over the pipe without glue, but they still need a clean cut. Cutting is usually necessary for a secure, leak-proof fit.