I had that exact problem a few months ago. The water heater worked fine for
years and then suddenly began to leak from the pressure relief valve. The
leak would generally occur just after a heavy use of hot water. I figured
the pressure relief valve had become defective so I replaced it. The new
valve did exactly the same thing. So, I purchased an expansion tank,
installed it and the leaking at the valve stopped and hasn't occurred since.
When I installed the expansion tank, I also installed a pressure gauge to
monitor the water pressure. It was initially at about 60 psi, so I reduced
it at the pressure regulator valve to about 50 psi.

I strongly suspect that the water company had increased the pressure or had
installed a check valve in the line (possibly when changing the water
meter). I also suspect that water companies are strongly opposed to any
water being forced back into the main lines because of possible
contamination problems and so they are prone to installing backflow
preventors. For all I know, water meters have backflow presentors built in
now days.

Harry

wrote in message
oups.com...
Since last week every time someone takes a bath the T&P valve
discharges a small amount of water. When this happens, the water looks
a bit rusty. If I pull lever on the valve, the rusty water will drain
and for a day or so there'll be no more leaks, then it starts again. I
checked the water line pressure and it's at 60 PSI.

I've replaced the valve and flushed the tank for about 30 min - two
days later the leak is back and water is rusty again when the lever is
pulled.
Any ideas?

thanks,
GE