Water Heaters - Electric heater safety valve overflow

I have five Rheems 50 gal. electric water heater. One overflow pipe is connected to three seperate heaters. I have two more connected to another overflow pipe. The first overflow pipe is leaking and I replaced one of the safety valves to the heater I thought was the problem. The leaking is continuing and mostly seems to occur during the night or early morning. It leaks about a gallon of water.

I contacted Rheems help line and was told that I needed an inline expansion tank for external pressure fluctation. But, why does the overflow only occur with the three connected to a single line and not the other two. I tried turning off the water to each of the heaters, but could not sustain that due to demands of the families. These heater have worked fine for over three years.

I would appreciate some suggestions on how to troubleshoot this problem as I am a novice about water heaters.

Unfortunately you'll get the same answer from most of us. Expansion tank. Not sure how your cold lines are tied in...but if pressure is being relieved from the 1, then the other 4 wouldn't leak.

Other possibility is the thermostats on the 1 heater are a little out of whack and they are overheating the water causing extra pressure in the 1 tank.

If your on a closed system, meaning you have a backflow prevention device on your incoming water, you should have a expansion tank anyways.

I agree with CSG that an expansion tank is needed. The size and where to install it is dependent upon the piping of these five heaters.

The reason that only one of the T&P valves is relieving pressure is due purely to the fact that these safety devices are not set to an absolute pressure but have a tolerance factor. You may be able to replace the valves on the three heaters with a manifolded drain and then get on of the other tanks to pop.

Or you may simply be playing musical valves among the several heaters and never find enough valves that are set within the tolerance and yet higher than the two other heaters.

Buck up, kiddo, even if you have to install expansion tanks separately on each heater it isn't that huge of a job.

Thanks for the reply. I can see where it might be as you suggest. With the single weakest valve leaking might be a consideration. As I mentioned two are on a seperate relief outlet of the three, but the same water supply and is not leaking. It is only the 3 with the same outlet that is leaking.

I called the water company in Tacoma and they strongly disagree with the possibility of pressure or flow fluctuation from the supply source to the extent that would cause the valve to release.

Perhaps I don't understand the hydraulics behind pressure and volume flow of the water supply. If I am compelled to add expansion tanks to all of the heaters, then I will do it, but I need to feel that it is ndeed the cause. After three years of not having a problem and then having a problem almost nightly, and there is no significant change in the water supply, leads me to want to look for something more logical.

Having replaced one valve, it could have been the wrong heater. I am considering purchasing two more valves to see what the difference is before going with the expansion tanks. It it continues to leak after 3 new valves, then I think your recommendation would be the most viable.

As to the thermostat, I would think that one would have to be going bad, as no one has adjusted them.

Is putting the expansion tanks on the individual heaters something that I could do. Is there instructions online for doing it?

Thank you,
Michael

You need just 1 expansion tank on the cold water line somewhere convenient.

I bet you do get strong objections on pressure and flow fluctuations from the water company. They deal with large mains and it is a big deal with these. On the lines your dealing with, the loss of flow from friction is much higher.

If the the 3 heaters are connected parallel with the supply line in the middle and using all the exact same lengths of piping and exact same fittings on the inlet side, then a common manifold built for the outlets using the same principal, you will have a pressure differential within the system in a static state. Chances are it's the closest tank to the supply line that is leaking. This will have the most pressure, not flow.

Don't want to go the expansion tank route, look at a PRV (pressure reducing valve with a built in bypass). install this and set pressure around 50 PSI.

Hope this helps.

Yeah, but if you install a PRV that acts as a check valve...your back to a closed system in which case you still need an expansion tank. :)

There are PRV's that allow water to bypass back into the supply system, due to over pressure. These only work when there is not a backflow preventer on the supply line or the meter set.

I was just making the statement so he was careful about which PRV to use IF he went that route.