I had a new water heater with extra anode rod installed for 10 year warranty. But because my water pressure measures 95 psi, I also need to get a pressure reducing valve (PRV) and Expansion Tank to meet code and preserve my insurance coverage. My concern is that expansion tanks typically only have a one year warranty. So how long can I expect the expansion tank to last?

One problem is that once the expansion tank goes, I'm no better off than I am now because every time I use hot woter, pressure will rise at least to 95 PSI to engage the internal bypass of the PRV. Fortunately, I am allowed to get a PRV with internal bypass, otherwise pressure would rise to the 150psi of the Temperature and Pressure valve (T&P).

I'm thinking I'd better replace the expansion tank every 5 years just to be safe. And be alert for changes in pressure meanwhile. Because my lowboy electric water heater is in the center of my house, I need to be sure that neither it nor the expansion tank will ever leak.

Another question is, how long can I expect the PRV to last, and especially the internal bypass feature of the PRV? And with all these extra parts which might fail and cause even higher psi, am I really better off than just living with the 95 psi as I have done for 10 years?

I guess I'm a bit confused.

Why do you think you need a PRV with an internal bypass instead of a regular PRV without one -- Are you on a well system?

Are you certain your local code requires an expansion tank on an electric H/W Tank?

With the H/W tank in the center of the house, how is the tanks T&P valve plumbed?

The local plumbing code requires PRV and Expansion Tank when line pressure exceeds 80 PSI. I'm not sure whether the code requires a PRV with internal bypass feature or not, but as I explained, I think it's a good idea, in case the expansion tank fails it's a second measure preventing pressure from rising to 150 PSI (or even higher, if T&P valve fails).

Local code is apparently not concerned with backflow, so I am not required to have a backflow preventer. Having a PRV with internal bypass means that backflow due to thermal expansion is permitted when system pressure exceeds line pressure. With an expansion tank this shouldn't normally happen so long as the expansion tank is working.

Going without both RV and Expansion Tank for 11 years, nothing has failed because of 95 PSI line pressure. I replaced the water heater now simply because it was old and due for replacement. 11 years ago, the previous water heater failed with a rupture sometime after the expansion tank failed. At that time, I was given the option of proceeding without an expansion tank so long as I also had the PRV removed also and signed a waiver.

It concerns me that expansion tanks aren't apparently designed to last as long as the best water heaters. Or so it appears. And when the expansion tank fails, you are in worse trouble than if you had no PRV.