determining the proper pressure for an expansion tank


Old 03-21-08, 03:39 PM
Member In Good Standing
Thread Starter
Join Date: Jan 2008
Location: usa
Posts: 159
Received 0 Votes on 0 Posts
determining the proper pressure for an expansion tank

My hot water heat system recently was more than doubled in the number of zones and length of pipe. The expansion tank needs to go from a 15 to a 30. Currently with the 15 tank the water pressure is about 12-15 # when the system is cold. It rises to 22-30# when hot, which is the reason for the larger tank. What is the proper pressure to charge the new tank before installing? I've heard 12 and also 15. The highest baseboard radiator is about 15 feet above the center of the boiler. Don't know if it matters but the house is at 8500' elevation.
Sponsored Links
Old 03-21-08, 03:54 PM
NJT's Avatar
NJT is offline
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 3 Votes on 2 Posts
The tank should be pre-charged to the same pressure as the system when cold. Anywhere from 12-15 is fine ... not super-critical. If you start with 15, and the tank will typically lose 1 PSI per year, then you won't have to mess with it but every 3 years or so.

If there is no isolation valve between the boiler and the tank, install one at this time unless your local codes dis-allow it. This will make later tank servicing much easier.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

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