We have a newly built townhome with a strange sump pump issue. The sump pump drain pipe runs underrated the master bedroom. It's PVC pipe.

Now the problem. When the sump pump runs, it hums so if you are in the utility room it is in, you can hear it. It actually sounds louder in the master bedroom a floor up and 25 feet away.

To get it to run less, we connected a flex pipe to the drain pipe outside our home, that caused water to back flow pretty loudly when the pump shuts off (sounds like a stream).

We have replaced the check valve and do not have any issues with the valve slamming shut.

So the questions:

1. The PVC pipe seems to be vibrating and amplifying the pump. Lise/vibration. What options are there to fix that. The PVC pipe from sump pump to ceiling is 9 feet. Could this be a bad pump causing the vibration?

2. How loud should a pump be when running?

3. Why does adding the exterior flex pipe cause the vacuum effect on the water?

Thanks