My hot water heater is leaking from the pop off valve, I have replaced it several times, and now I have a new heater, and guess what it is leaking through the pop off valve. I have had 4 different plumbers check this out, they put a new regulator at the water meter, turned the temp of the water down, replaced every thing in the old heater. I have a new one, and it has started to leak, I give up.
If I were you I would demand refunds from your plumbers and sell your old water heaters for they are still in worrying order. The tmps are not whats malfunctioning and the plumbers you called must be want to be's. You have a pressurization problem in your water system it is very common. The answer to your problem is you need to install an expansion tank in the system. Whatever you do, do not cap the tmp, if you do you are creating a "bomb!" If you cant get it to stop I would shut the water feed to the heater when you dont need hott water call a company that knows about installing an expansion tank in your hot water system and your headache will be taken care of. Im sorry for all the bad luck with those other plumbers I am very surprised none of them ever mentioned it.
I have a 50 gallon heater, and the valve that was installed at the water line decreased the water flow, all this was checked, it is a standard house water heater, there is no need for a reserve tank
Here is an article on expansion tanks and why you need one.
An expansion tank has nothing to do with being a reserve tank. It has to do with hot water expanding and contrapting and keeping your tmp from opening up when it doesnt need to. Please just read the article and educate yourself on them..Dont forget this is what I do for a living.
The prv they installed at the mainline is doing nothing but reducing the psi's going into your home. The tmp is set to mutch higher psi & temperature. It is easy to isolate your problem to the hott water not the water feed, just read the tag that comes on all the tmps they have a preassure rating at witch the will set off your water heater is the only thing that can heat water up to those psi to make it go off.
every time I go to the link you sent I get kicked off line so I haven't been able to see an expansion tank
do these come in different sizes and if so what size would you recommend for a 50 gallon
They make small ones for residential they are not very big I would like to call it a 5gal not sure off top of my head if I saw it I could point it out. They will proble mount it on the ground or up high in the corner of wall.
10+ years experiance in the pipe industries.