Water heater TP valve leaking after shower removal

[min10]

Hello,

I removed a fiberglass shower to install tile, and shortly afterward, my water heater started leaking from the temperature/pressure relief valve. I have drained the water heater, replaced the TP relief valve, lowered the water temperature setting, and lowered the inlet water pressure, all to no avail (lowering the water pressure slowed the leak, but it's still present).

When I removed the shower head and mixing valve, I shut off the main water supply, and capped off the hot/cold water pipes by soldering caps onto the ends. Could the introduction of air into the shower pipes (from an upstairs bathroom) have caused a leak from the water heater TP relief valve (in the garage)? If this is plausible, would installing temporary valves that would allow me to bleed out any air from the shower water lines help?

Many, many thanks for any advice you can offer.

 

[Mr_David]

You said you lowered the inlet pressure.
How? What is the pressure now?


If you don't know what the pressure is, how do you know you lowered it?

 

[min10]

There's an existing whole-house pressure regulator that I adjusted. I admit I don't know the exact pressure, but it's significantly lower than it was before.

 

[frodo]

did you at any time, open the T&P valve ?

 

[min10]

Not before the leak started, but I did open the lever on the old one to release pressure before draining the tank and replacing the valve. I also opened the lever on the new one to check functionality. Bad idea...?