Low pressure 25l underbench hot water cylinder (Rheem).
There was a leak in the pipe on the top part of the cylinder. It must have leaked for months because there was extensive gradual damage around the walls, carpets in the lounge next to the cylinder. That was fixed by the plumber then several days later the overflow leaked HEAPS like a running tap.
We replaced the washer of the reducing valve. It leaked again but dripped first then gradually leaked like a tap. But not as bad as running tap.
Today we replaced the reducing valve with a new one. Several hours later it’s leaking AGAIN like a running tap. Ahhhhrrrrggggghhh…
That Temperature/Pressure releif valve is doing was it supposed to do. Replacing it will not stop the problem. Either the pressure or the temperature are exceeding set limits, check both. Never, ever remove this valve and plug, for it could explode without this releif.