Home boiler- Expansion tank
Any idea on what the psi in that expansion tank should be?
I want to try adding pressure to it.
I’m hearing a new noise pattern that I think sounds like expansion-type noises. There is some regular drainage too from what I think is a pressure relief valve.
thanks, Ed
Replies
Your pressure should be approx. equal to the operating pressure of your system, if you are talking about a heating system the pressure should be in the 12lb. range. If we are talking about a water heater you will have to check your incomming pressure and go with that no. If you try to pump up the tank and it won't hold, you need a new tank. Hope this helps.
If you have the old type expansion tank (where the water and the air are in contact with each other) you may have a waterlogged tank. You can usually bang on the side of the tank with a metal object and tell where the water line is.
If you have the newer bladder style (with the bladder separating the water and the air charge) you may have a ruptured bladder or not enough air pressure in the tank.
It is also possible that you have a defective pressure reducing feed valve on your main supply line, which is letting the system pressure in your boiler build up too high.
Unless you have been messing with the relief valve and it got a bit of debris in it, the leaking valve usually indicates a pressure that is too high for one reason or another.
if this is on a hot water heating system and is an older bladderless tank you need to drain the expansion tank periodicaly as the air in the tank becomes saturated and will no longer work as intended and cause the pressure relief valve to leak. There should be a valve on the bottom of the tank and a valve to isolate the tank from the rest of the system. Isolate it and then open the valve on the tank to drain the water.
If it is not a hot water heating system then nevermind.
I have a tank with a bladder.
I went and pumped it with a hand air pump. I couldn't get an accurate pressure reading off the valve. So I don't know where the pressure in the tank is right now. I'm approaching the whole thing on a trial and error basis.
I know that I have the system pressurize to well over the 12psi recommended by Shacko. That 12psi really caught my attention. The boiler gauge reads 24 psi. I'm responsible for that because the first thing I did yesterday was to manually override the pressure limiting intake valve to get some more water in there. At that time I noticed the unusually low boiler gauge pressure.
Adding air to the expansion tank has reduced the frequency of the expansion noises. The noises are still there. I'll keep working with this over the next few days, get the boiler pressure down, and then try adding some more air.
I'll replace the tank if I need to, but I would really rather wait until after the heating season before taking on the risks of shutting down the system.
Thanks to everyone.
You left a few details out of your original post??!!
1) Was your automatic fill valve open when the boiler was in service? If it was, you either have a sticky fill valve ( which is common) or you have a leak somewhere in your boiler piping system, or perhaps both.
2) How low was the "unusually low" pressure on your boiler gauge?
3) You should immediately drain some water out of the boiler and get the pressure back down to around 12 psi when it is cold.
4) What happened when you went to put air in the bladder tank? If you didn't see any sign of water, it's not ruptured.
5) Get yourself a good pressure gauge and make sure you have 12psi in the tank.
6) With your boiler pressure down just below 12 psi, let the automatic fill valve build the pressure up to 12 psi, just to see if it is functioning properly.
7) I would install a backflow preventer in the feed line before the fill valve when you get an opportunity.
8) The "expansion" noise you are hearing could be water about to boil in your boiler if your water is low and the pressure is down.
9) Check for system leaks.
10) If you have piping below the boiler, I would also install a low-water cutoff.
Good Luck!
One other thing to add, you can't check the pressure in the tank unless it is isolated.
Add a isolation valve and a boiler drain between the iso and the tank. Close the iso, open the boiler drain, then check the pressure in the tank.
Let a little air out of the air fitting to make sure no water comes out. If there is water,you need a new tank.