I finally got around to replacing the T&P Valve. As I was shutting the cold water off I noticed something I hadn't before. I seem to have to cold water lines that run together at the heater. Once has the cut off valve, the other doesn't. Turning the valve off did stop pressure to the tank. I'll be darned if I have any idea at all what the second line is for. I also noticed the copper pipe with the cutoff valve has something that looks like a solenoid maybe with '50 psi' printed on a green and white metal disk at the top. It has been 2 weeks since I replaced the valve. I ran all water sources in the house until all the air was gone. I only get a little bit of water out of the new T&P valve now. This is discouraging, but it is a small amount. Maybe 1 inch in the bottom of a 5 gallon bucket in two weeks. I do have one weird thing. When I flush the upstairs toilet now the pipes (not the toilet) upstairs make a moaning like noise until the tank is full. Today, the other upstairs toilet started doing this. The first toilet started doing it the very first night. If anything, I expected a water hammer. I don't have that. Call me mystified. I have never heard this in any house I've lived in. Thank you for any idea's you may be able to offer folks.