For starters my home is about a year old. The other day I added a thermal expansion tank because the pressure relief valve popped off causing water to drain from the hot water tank. i followed the instructions:

1. Checked the themal expansions tank pressue to insure it was 40 pounds.

2. Install the thermal tank

3. Drain the hot water tank so water was below the pressure relief valve. Open the pressure relief valve.

Next I opened all of the facwetts (inside and out) and flused the commodes. Then I opened the main water. After the water started to flow, I shut the the vales off staring at the lowest point.

I left a hot water facett drip until the hot water tank quit heating.

I no longer have a promlem with the pressure. it stays around 58 pounds.

BUT NOW I GET A SINGING NOISE A FEW SECONDS AFTER A FACWETT IS SHUT OFF OR COMMODE SHUTS OFF.

The noise appears to come from the main shut off area, but, I cannot be sure.

Any suggestions on how to identify the problem area or possible solutions.

regis