Having a check valve will make sure that the water lingering in the sump pump’s discharge line does not flow back into the basin of the sump pump after you shut the pump off.
 Make sure that you have everything you will need throughout the entire process to be better prepared. You will need the following:

Tape measure
Pipe cleaner
PVC cement
PVC cement applicator
Utility knife
Sump pump check valve
Adapters or couplings
Pipe cutter

, Pay attention to the diameter of your existing discharge pipe. You can go to the local hardware store and buy the corresponding check valve (which comes with the correct diameter). It is important that you do not buy a valve with a smaller diameter than your current drainpipe.,  If you are going to a hardware store, it is a good idea to bring a sample of your pipe with you if possible. This allows you to try to fit the valves with your pipe, just to be sure that you have a good fit. Because there are so many different valves available, you can opt for whatever suits your needs., You also need to make sure that you buy the adapters or couplings that are going to fit according to the size of your drainpipe. Again, if you are unsure, having the pipe with you at the store is going to eliminate a lot of the confusion., You also need to make sure that you buy the adapters or couplings that are going to fit according to the size of your drainpipe. Again, if you are unsure, having the pipe with you at the store is going to eliminate a lot of the confusion., Just to be sure, before you ever get started, you should turn off the electricity to the pump. If you want to be extra cautious, make sure that you unplug the sump pump altogether., Now you have your sump pump check valve. The next step is looking at the discharge pipe and figuring out where exactly you should place your check valve. The traditional option is to have it close to the sump pump itself, next to the sump pit. This is going to ensure that you do not have too much water trapped between the pump and the check valve., Use a pipe cutter to cut the discharge pipe in two places. This is going to ensure that there is enough room to fit your new valve. You want to make sure that you do not cut too much of the pipe right away. Instead, measure first and then cut little by little. It is better to have to cut the pipe two or three times than realize that you took out too much., After you have made the cut the right way and you are happy with the result, you can smooth out the edges of the pipe. You want to file down the edges of the pipe as much as possible in order to smooth them out., You have a gap in your discharge pipe, now you want to fit the check valve into the recently created gap. If you were secure in determining the appropriate size at the start and with your cutting of the pipe, you should find that the valve actually fits perfectly., Both ends of the discharge pipe go into both ends of the valve. Now all you have left to do is secure it. Join all the ends together by using the couplings., If you have your sump pump check valve in place, you will now want to seal the points of contact. Use some PVC cement to create a good seal. Grab an applicator, put some cement on the applicator, and apply the cement across the gaps between the connections., Before you try your sump pump check valve make sure that you thoroughly clean the area. There should be no more open gaps., Now we have arrived at the final test, actually running your valve for the first time. In order to test your check valve, you have to open the pump and pump in some water from the sump pit. Pay close attention and listen carefully when the initial water pressure runs through the valve. You should be able to hear the flap inside of the valve open as the water pressure increases.
Understand why installing a sump pump check valve matters.The installation of a sump pump check valve is vital to the functioning of the entire system.
Make sure you have what you need.
You need to have the right tools for the job.
Bring a sample of your pipe.
Buy the right couplings.
Drain the basin.
Turning off the sump pump.
Locate the discharge pipe.
Cut the pipe.
File the edges.
Fit the valve.
Fit both ends together.
Seal the points of contact.
Let the cement dry.
Test your sump pump check valve.
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