What is a Thermal Expansion Device for a Hot water heater and how do I install it?
I have been told by a plumber that I have to bring my NEW hot water heater up to code, but I don't know what he is talking about. We installed (by ourselves) a brand new hot water heater 5/3/00 and it is leaking at the relief valve. The warrantors said I have to bring the installation up to code before they will fix it!

 

Thermal expansion occurs when your hot water heater cycles to heat water after use. The water wants to expand everywhere in your house but new restrictors probably at the meter now do not let pressure relieve itself back across the meter. Since water is incompressible, it builds pressure. The T&P relief valve purges if no other pressure relief is available (such as running a tap or flushing a toilet). This can occur numerous times, typically at night after hot water use and then no one uses water until the next morning. The T&P valve on the hot water heater is not made for cycling. To fix the problem, install a thermal expansion tank in line with the hot water heater OR get a governor ballcock for one toilet. Either device will allow the expanded water somewhere to go. Until you fix this, all items in your house are experience increased pressure during the reheat cycles. Lots of people are just getting educated on this, myself included. I had to convince my own plumber that I had an expansion problem. He didn't agree until he had replaced 2 T&P valves AND the house pressure regulator and still didn't fix the problem. You can convince yourself of the increased pressure by putting a pressure gauge ($10) on the faucet outside your house (not the street pressure faucet) and checking it. If the heater has cycled and no one has used any water, the reading can be over 80 psi. As soon as water is run or a toilet flushed, the pressure will drop.

 

Thank you very much for your help! I appreciate you getting back to me so quickly! Have a happy day!

quote:<HR>Originally posted by kevin:
Thermal expansion occurs when your hot water heater cycles to heat water after use. The water wants to expand everywhere in your house but new restrictors probably at the meter now do not let pressure relieve itself back across the meter. Since water is incompressible, it builds pressure. The T&P relief valve purges if no other pressure relief is available (such as running a tap or flushing a toilet). This can occur numerous times, typically at night after hot water use and then no one uses water until the next morning. The T&P valve on the hot water heater is not made for cycling. To fix the problem, install a thermal expansion tank in line with the hot water heater OR get a governor ballcock for one toilet. Either device will allow the expanded water somewhere to go. Until you fix this, all items in your house are experience increased pressure during the reheat cycles. Lots of people are just getting educated on this, myself included. I had to convince my own plumber that I had an expansion problem. He didn't agree until he had replaced 2 T&P valves AND the house pressure regulator and still didn't fix the problem. You can convince yourself of the increased pressure by putting a pressure gauge ($10) on the faucet outside your house (not the street pressure faucet) and checking it. If the heater has cycled and no one has used any water, the reading can be over 80 psi. As soon as water is run or a toilet flushed, the pressure will drop. <HR>