Hi,

I have a hot water furnace(Hydro-Therm) baseboard with a seperate water heater. 2-zone system. has an automatic air eliminator. 2-story home. there is no shut off valve going to the expansion tank.

Problem: I noticed that the Extrol expansion tank air valve is leaking water. This past heating season, the furnance ran great, the water temp=170F and the pressure=18-20 psi.

My questions:

1. I believe the expansion tank is shot and needs to be replaced. i tapped the side of the tank all the way up to the top with a hammer and it sounds like it has no air in it.
2. Can someone provide the method for draining the system, replacing the expansion tank, and refilling and purging any air? I noticed that the system has 4 drain valves; Zone1(ground floor) has 1 drain; Zone2 has 2 drains and there is 1 drain next to the water pump that looks like it has never been opened.
3. Expansion tanks. Home depot has a Watts expansion tank ET-30, 12 psi sealed tank for $32.00 but it is a sealed unit with no air valve. what do you folks recommend?

sorry for the long-winded post, but i wanted to give as much info as possible. tia

 

NOTE: To make future replacement easier, it would be a good idea to install a valve between the tank & where it connects. I like full port ball valves.
I do not suggest a tank without an air valve. Get the new tank. It should be pre-pressurized to 12#. Use a bicycle pump or small compressor to increase the pressure to 15#. Check the pressure with a low pressure tire gauge. Apply teflon tape or pipe dope to the threads. Have the tank sitting as close as is practical to where it will go. The idea here is to do a quick swap. Turn off the power to the boiler & all the boiler related valves you can find. Use a hose (washing machine hose works well) from the bottom drain valve into a bucket & drop the boiler pressure to zero by draining water via the drain valve. When the pressure is at zero, close the drain & unscrew the old tank (CAUTION: When it comes loose it will be heavy) & screw the new one in it's place. Open the water feed valve slowly & pressurize the boiler to about 15#. After the boiler is at pressure, open the valves you closed (except the drain, obviously), restore power & set the thermostat for the second floor to call for heat. With luck, you won't have to purge air from the system.

 

Grady many thanks for your reply!

i was able to replace the expansion tank without a hitch by following your excellent suggestions.

 

My Honeywell setup came with an automatic cutoff valve between the SuperVent and tank. Small spring loaded cutoff--about 1/2" long. Not sure how good it will be when I need it to work, though...

 

Glad it went well. If you installed the valve, the next time will be pure gravy. You won't have to purge air at all. Start to finish 10 minutes max.

 

Grady glad you cautioned about the tank being heavy one other caution for the future is don't tighten to much, the air scoop is only cast and I have had to replace many because of someone changing the tank and screwing the new one in way to tight!

 

Thank you. You are absolutely right. I use no tools when installing a new tank. Teflon tape on the threads & hand tight is plenty. You can get a good bit of leverage just by using your hands on the tank.

 

Your instructions to replacing the expansion tank was very helpful.. It was done in about 20 minutes.. Thank you

 

In replacing a new expansion tank, I have a ball valve between the tank and the connection. Do I still have to reduce the pressure and shut off all the valves?
Also si it necessary to refill the burner to ppressure and how .

 

To prevent the tank from blowing off as you unscrew it, it's a good idea to drop the pressure. To prevent loss of water out of the system, close all valves you can find.

 

Donnie, if you have the room below, you can add a tee with a drain on it between the ball valve and the new tank. This makes it even that much easier.

 

can i replace hydronic with diaphragm expansion tank?

 

Kevin, I think your terminology may not be correct.

Hydronic = a cooling or heating system in which heat is transported using circulating water.

I think you are talking about replacing a large steel 'compression' tank that is above the boiler with the modern type, correct?

Yes, it can be done, but there is more to it than meets the eye.

Why would you want to?

 

Nj

I'm really new to the terms so let me explain.. I was told I needed to replace my expansion tank and went out and bought a new one, after the instal I realized that both tanks (old,new ) had different labels . Old - pressurized tank with diaphragm and the new one is hydronic expansion text, my concern is that the difference might be damaging to my system ..also my psi is still really close to 30 which was the issue with old tank...

 

Kevin, I've just had the same thing happen to me, please say more about the brands of your "new & old" tanks. I had previously bought an EXT-30 Watts tank (knock-off?) at Home Depot , but then my plumbing supplier commented it was made overseas and that for just a few bucks I could buy Amtrol's true EXTROL-30, made in NJ, USA.

Phgs - How right you are. I've just discovered that some gorilla must have installed my expansion tank, seemingly without using joint compound, badly rusted and impossible to remove! Even soaking with WD40 and pounding my 7/8" wrench with a steel mallet (counter-clockwise looking upward) will not budge!

Next my plumber will need to cut & replace more pipes in that area - Thanks for the advice.

 

Hi Kevin, thanks, I understand your question now...

The new tank which you purchased is the same 'type' of tank as the old. It should also be the same CAPACITY in order to work properly, size matters here.

Quality does differ from manf to manf ... but if the tank is properly maintained with yearly, or at LEAST semi-annual, checking and adjusting of the air charge any tank should last a good long time.

Read this for instructions on how to properly maintain the air charge, there are step by step instructions included:

http://www.doityourself.com/forum/bo...sion-tank.html

Read this for why you should never trust the pressure gauge on your boiler:

http://www.doityourself.com/forum/bo...ure-gauge.html

There are more than one reason for high boiler pressure. The expansion tank problem is number one.

1. Expansion tank has either low air charge, or defective rubber membrane/bladder.

2. PRESSURE REDUCING VAVLE ( aka "automatic fill valve" and other names ). This is the pressure regulating valve that feeds water to your boiler system and they will sometimes leak through... you won't see a leak because it is internal. This valve has city water pressure on one side and is supposed to drop that city pressure to the 12-15 PSI required by your boiler. If they develop an internal leak, the boiler pressure will rise.

3. If your boiler is also used with an internal coil to heat your domestic hot water this coil may develop a leak and pretty much do the same symptom as the pressure reducing valve in #2 above.

I would recommend that you first follow the step by step instructions to be certain that you have the expansion tank properly charged. Then test... and see if this corrects the trouble.

If not, next suspect the pressure reducing valve. This can be diagnosed by properly setting the boiler pressure when the system is COLD and then CLOSING THE MANUAL WATER SHUTOFF for a few days and monitoring the boiler pressure in the meantime. If the problem stops when the manual valve is shut, the pressure reducing valve is bad and needs replaced.

If you have a tankless domestic coil, the process is basically the same... shut off the supply to the boiler and monitor... you will be without domestic hot water during this time.