Leaking Indirect coil causing Boiler Pressure to increase= pop of t+P

I really appreciate all of this input.
My current status is:
Boiler pressure still between 20 and 28 PSI. Auto-fill still off. 30PSI Pressure Relief Valve Still dripping.
Assuming a pin hole in the Water Heater, should not the pressure in boiler approach domestic pressure? Or is the PRV preventing that?
I was replacing these PRV's so often that I've install a valve between it and the boiler as not to have to drain the whole system for replacement.
Question, if I close that valve, will I then see pressure increase towards the domestic pressure because there is no PRV at this point?
Hmmmm?

Shut off the water to the water heater, drop the boiler pressure to 12 lbs and wait. If the pressure stays at 12 lbs the water heater is leaking.

Tom Sawyer said:

Shut off the water to the water heater, drop the boiler pressure to 12 lbs and wait. If the pressure stays at 12 lbs the water heater is leaking.

Click to expand...

OUTSTANDING!!!!!!!!
Thanks Tom.
Conducted that experiment this morning. Turned off domestic feed to Hot Water Heater and opened a hot side faucet to relieve pressure. Watched the boiler pressure go to 12!
Funny thing though, When I turned the domestic back on, it blew out the PRV violently. Guess I opened it too fast.
YOU GUYS ARE THE BEST!!!!!!!!!!!!!!
WISH I HAD YOU HERE TO SWAP IT OUT!