Expansion tank

I am confused as to what they call a closed system and the need for an expansion tank.

Currently i have a lp gas 40 gallon water heater tank. no expansion tank, been in use for 10 years, no issues.

Switching to electric 80 gallon heat pump water heater. Keep reading about expansion tanks.

I have city water, meter is 1000 feet up my driveway. I have no pressure reducing valve or any restrictions on my 2" line coming from the road. 2 inch black poly line coming in the house. It drops to 1 inch copper in the house, then feeds 3/4" to my water heater. 1" line feeds a fire sprinkler system. Never been used, thank goodness.

Is this a closed system and do i need an expansion tank?

Thanks

A closed system is when thermal expansion or excess pressure from expansion is unable to get pushed back to the city main. An expansion tank is designed to absorb this excess pressure. Some pressure regs have a bypass built into them to allow the pressure to go back into the city. Here is the issue. If city pressure is lets say 95psi and your expansion is 85psi then the pressure you are creating cannot push the city pressure back so other fixtures will absorb this expansion which will lead to leaks or blown pipes. You want to set an expansion tank to the same pressure as you house pressure. Alot of time the t and p valve will start to leak if presure gets to high which is what you dont want. Also that black tube or black poly you have is going to be an issue somewhere down the line. In my area it is code to install an expansion tank. The code states on a closed system but the bylaws state it needs to be installed on every heater. The expansion tank mounts on the cold inlet with a check valve. It needs to be properly braced also

OK, Thanks.

I will find out the pressure of the city system at my house. I know it picks up a few pounds running down my driveway, it drops about 30 feet from the meter set.

I have always had city water in the 4 houses I have lived in (all had gas water heaters) and none had an expansion tank.

The water pressure at the spigots in my current house is 60 psi. Do I need an expansion tank?

Why do you say the black poly line will be an issue? That is a 2 inch line that has almost a 1/4" thick walls. It ain't the crap you buy at home box stores.