Do you have to install an expansion tank on electric heaters if you are using Pex?

Hi Winglover

In most states, you are not required to install an expansion tank at a water heater unless you have a closed water system where you have an pressure reducing valve, a check valve or other similar device installed on your water main. Here, these types of devices stop water from flowing backwards and therefore when water expands due to heating the expansion has no where to go so it will usually leak out the relief valve of the water heater or boiler. An expansion tank is installed in these cases to "absorb" the expansion via air pressure and a neoprene diaphragm inside the tank.

Finally, you should not connect PEX directly to the water heater... come off the heater about 18" with copper or brass and then transition over to the PEX. If you connect the PEX directly to the water heater and it should ever overheat the PEX connections can weaken and burst off the pipes, OK?

Any more questions just let me know, OK?

Mark

Thank you very much!

:)