My sump pump runs but but does not discharge. I have noticed if I release some pressure by way of loosening hose clamp where check valve connects, I re-tighten then pump will discharge water perfectly for about 20 seconds then reverts back to no discharge. It is like I keep getting air blockage? Can this be the problem?

Is it at all possible that the check valve is reversed? If not it has failed and needs to be replaced

Is it at all possible that the check valve is reversed? If not it has failed and needs to be replaced

Thanks for you response. Do u mean pump has failed or check valve?

OK, this is getting confusing. Is this a new or existing installation?

What side of the check valve did you loosen? Pump side, outlet side?

What does the piping look like. Rises and runs. i.e. How far up does it have to pump?

Some pumps require a small hole at the pump in the discharge pipe. This is usually about 1/8" diameter. This prevents the air lock. It's called a weep hole.

Inspect the check valve.

I am thinking your check valve hasfailed or its reversed. Answer KISS's question , which side of the valve did you loosen, above or below the valve.

Actually, the first two times I removed the "outlet side," then I realized that if I removed the "pump side" it would make a less water mess. Either way, the result was the same. Pump would work great for about 20 seconds then just hum and eject no more water. I thing I have what is called an "open system," meaning the eject pipe runs up my basement wall, goes outside, then elbows down into city sewar pipe that is lager than my pvc... so it is open. Outside air can easily come in and out of my pvc. Sorry if I am not explaining this right. But my check valve seems to be fine. Yesterday I was able to get it working for about 2 hours, it was running through its cycles fine, then just stopped working again. Could the pump just be getting weak and allowing the water to fall back and close check valve? I did not notice a weep hole at all. The pump has worked fine for 4 years until now. Thanks.

Run it until it hums, them open they ckeck valve connection. Was there water trying to be pumped or just the hum? If it was just a hum, replace the pump.

Thanks for the help guys. I decided to just change out the pump for peace of mind. All is working fine now. Thanks again!

Great! Had to be one or the other.