Help sizing the Expansion Tank.


Old 10-26-11, 09:47 PM
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Help sizing the Expansion Tank.

We just had our Hot water heating system replaced with a Burnham. Used the system for a few days, and now I noticed the pressure relief valve had spilled some water.
After a week of trying to reach the plumber that installed the system, unfortunately, I found out that he got hurt and is hospitalized for about a month. I explained to him what was going on, and he emailed back that we have to replace the Expansion tank to a size 60, or add another 30 size tank to the existing tank.

The house is about 2500 s.f. It has 8 good sized cast-iron radiators, and the whole second floor is Baseboard (fin type). The system is 115,000 BTU.

Does this sound right? Do we need the 60 size tank, and would that solve the issue of leaking water when hot.

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Old 10-26-11, 11:27 PM
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That would be correct, I would say a 60 size.

Possibly a 90 size if large amounts of water.

Here is some data.

Make sure you secure it properly. Straps...etc... Those suckers get heavy when they fail.

Mike NJ

Last edited by NJT; 11-18-11 at 05:43 PM.
Old 10-27-11, 05:00 PM
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It would be a good idea to add a few things to your expansion tank pipe when you change it. If you don't already have one, add a ball valve so you can isolate it from the rest of the system for maintenance. Next, add a tee after the ball valve. Put a length of pipe with a hose bib at the end. The idea of this is so you can check your tank pressure every year easily. You shut off the ball valve and open the hose bib to bring the pressure down to 0. You need to the pressure at 0 to properly check the air charge in the expansion tank. The pipe with the hose bib should be long enough so you can put a bucket under it to catch the water. You could also attach a hose to it. More water than you think will come out of there.
Old 10-27-11, 05:45 PM
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Thanks a lot lawrosa and drooplug. It all makes sense, and I'll try to do all that you suggested.


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