I have read tons of your humming pipe problems, but none are exactly like mine. I have a 2 stroy home and I have my own well. A year or so after flushing the upstairs toilet, when it was nearly full of water it would hum until it was finished filling. Then it would quit. It didn't do it all the time but now and then. Sometimes it would go for several months and then hum again for a few days. Recently it started humming again. Oh, and it always stops when I flush that toilet. But now it happens regardless if using the upstairs toilet. BUT it doesn't do it at the highest pressure point. It always does it when the pump is re pressurizing the system. I hear the pump come on and then about 40 psi or so it starts humming and hums until the pump shuts off at about 62 psi. It never hums while the pressure is up and pump not running. The hum will still quit if I go upstairs and flush that toilet. It will not stop if I open any other valve including the downstairs toilet. I took the drywall off that exposed the supply pipe going to the upstairs toilet and everything is tight without vibration. When the lawn sprinklers are running the pump never shuts off and holds pressure around 60 psi and it NEVER hums, Any ideas?