100 psi is too high. Reduce pressure to 55 psi for the house and to 90 psi for the sprinkler system. There is a chance that pressure is blowing through your seals. This could happen just about on any plumbing fixtures and also at the anti-siphon valves outside.

The loud hum is being herd all over---it is the shuman resonance and it is getting louder. It is caused by solar activity most believe(the new loud very low frequency sounds that are being herd all over the world.) v l f as it is called ------ 2012?? John king

It sound the same as what we experience. Every night between 1130 and 12. Then stops at about 4 am. My husband hears it too so I know its not just me. We also live in a ranch style in the country. But we do have power lines across the street.

Look for leaks near the well pump. We replaced a pipe with a tiny leak and it made the house quiet again.

We actually heard it really loud Sunday morning which usually we don't hear it in the morning only at night. So my husband decided to try turning off all the power to the house at the circuit breaker and guess what it stopped. Now I am concerned that we are actually hearing the humming of an electrical current coming into our house. Is this normal or should I be calling our electric company??

Have you tried shutting off each toilet to see if the flush valves are the culprit?