My dad installed a check valve on his sump pump... it works but the float doesn't turn off when the sump is empty... WHERE should the check valve be place on the system? Closer to the pump? Higher up on the vertical line? Or should it not matter and he has a different problem?

We always place the check valve next to the pump. Place it anywhere else and you'll have all the water in the hose drain back into the pit once the pump stops. Regards, Tom

Are you talking about Check Valve or Float ? Please verify...

Check Valve: What kind of check valve is it ? Flopper type or spring loaded ? What position is it installed in ?

There is also a possibility that there is debris inside the valve preventing it from closing. Also, make sure it is installed with the flow.

Float: If float doesn't turn off than one of 2 things may be happening:
1. Debris preventing float from going freely up and down
2. Float is installed too low or hitting pump or side of the pit

Best is to open up the pit, put in garden hose, open water - and watch the pump operate.

It is a check valve. I'm not sure what kind. I'm not there with him - but he installed the valve to his existing system (which has never had a problem running) about 12-15" up from the pump on the vertical line - when he checked it the float will not turn off... He is going to move the check valve closer to the pump and see how that works... he said it's a flopper type and it has an arrow to follow the water flow.

Thank you Milo and Speedball1 for the quick replies! I appreciate your time and knowledge!

It appears to me the float is hitting the check valve, preventing it from switching pump ON and OFF. Make sure float has enough space so it can freely operate.