Water Heater Themal Expansion Tank... Needed?


  #1  
Old 09-04-14, 12:02 PM
S
Member
Thread Starter
Join Date: Dec 2006
Location: USA
Posts: 97
Received 1 Vote on 1 Post
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.
 
  #2  
Old 09-05-14, 06:58 AM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,853
Received 114 Votes on 101 Posts
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  
Old 09-05-14, 07:15 AM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,161
Received 69 Votes on 61 Posts
Increasing the size of the tank is not in the equation.
Usually it is.. Bigger heaters have bigger burners sometimes with a 40 to a 50...

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  
Old 09-05-14, 06:54 PM
CasualJoe's Avatar
Member
Join Date: Jan 2010
Location: United States
Posts: 10,853
Received 114 Votes on 101 Posts
Increasing the size of the tank is not in the equation.
Usually it is.. Bigger heaters have bigger burners sometimes with a 40 to a 50...
I guess I should have said, in my opinion the size of the tank is not in the equation because I am not a plumbing pro, but I have had some experience. The way I see it, installing an expansion tank when there is no check valve in the meter will allow the service line and expansion tank to equally absorb the added pressure created by the water expanding as it heats. Yes, a larger tank would mean more volume is being heated which would normally increase the pressure in a closed system even more, but when a system isn't closed I see no need for the expansion tank and have never seen one in a community that doesn't have check valves in their meters. Is an expansion tank required by code when there is no check valve?
 
  #5  
Old 09-05-14, 08:10 PM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,161
Received 69 Votes on 61 Posts
Is an expansion tank required by code when there is no check valve?
Yes,,,,, as I stated below with higher output burners....
 
  #6  
Old 09-06-14, 12:38 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
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.
 
  #7  
Old 09-06-14, 06:49 AM
lawrosa's Avatar
Super Moderator
Join Date: Dec 2010
Location: Galivants Ferry SC USA
Posts: 18,161
Received 69 Votes on 61 Posts
I think NJ they decipher it from the gas code..?

But I would have to dig into the code..

Also It could be a town requirement just because of the inspector...
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: