Water Heater Themal Expansion Tank... Needed?
#1
09-04-14, 01:02 PM
Water Heater Themal Expansion Tank... Needed?
Getting ready to replace a 15 year old water heater and was wondering if I should also install a thermal expansion tank. Currently, there is not one.
I am thinking about installing a 50 gal heater to replace my 40 gal. Would this be any reason to install a thermal expansion tank?
Thanks in advance.
I am thinking about installing a 50 gal heater to replace my 40 gal. Would this be any reason to install a thermal expansion tank?
Thanks in advance.
#2
09-05-14, 07:58 AM
Member
In my area thermal expansion tanks are required and necessary because as the water company replaces water meters, the new meters have a check valve that keeps the thermal expansion from pushing back to the street. Some pressure reducing valves also have a check valve that causes this as well. The result is the pressure in the closed water system within a house exceeds the pressure rating of the Temperature & Pressure relief valve (I think 150 PSI is common) on a water heater as the water heats and expands and water is forced out on the basment floor through that safety valve. Some areas in MO do not have the check valves in the meters. I think I'd suggest checking with your local building office (AHJ) and ask them if they are required. Increasing the size of the tank is not in the equation.
#3
09-05-14, 08:15 AM
Super Moderator
Increasing the size of the tank is not in the equation.
IN NJ a 75 gal heater has 75K btu burners.. They are required by code to have an expansion tank..
IMO a expansion tank is good for any heater if check valve on the main or not.. Helps prevent bulging of the heater that puts stress on the seem....
If your on a well then the well tank acts as an expansion tank..
Last, most expansion tanks are set to 40 psi from the factory.. Most dont know but you need to set the exp tank psi to the homes static pressure before you install....
#4
09-05-14, 07:54 PM
Member
Increasing the size of the tank is not in the equation.
#6
09-06-14, 01:38 AM
Join Date: Mar 2006
Location: Wet side of Washington state.
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The Uniform Plumbing Code (UPC, applicable in my area) makes no mention of an expansion tank being necessary EXCEPT when a check valve in the supply piping makes it a closed system. There is no expansion tank requirement based upon the BTU input of the burner. There ARE other plumbing codes besides the UPC and any LOCAL code may add to or delete from the model code when enacted into law.
That stated, water utilities across the nation are slowly, but surely, replacing their meters with models that DO incorporate a check valve. I think (don't know for certain) that this retrofit is because of a USEPA requirement. Adding an expansion tank, sized for the amount of water in the heater, simply makes good sense since the water utility does not need to notify you of their using a check valve type of meter.
That stated, water utilities across the nation are slowly, but surely, replacing their meters with models that DO incorporate a check valve. I think (don't know for certain) that this retrofit is because of a USEPA requirement. Adding an expansion tank, sized for the amount of water in the heater, simply makes good sense since the water utility does not need to notify you of their using a check valve type of meter.
