Expansion Tanks

Mike T., Swampeast MO

If bladder-type tanks loose a bit of charge (1-2#) per year and you have to bring the system down to 0# water pressure to accurately check the air in the tank, do you routinely drain the system every year?

I know people seem to hate plain tanks because they tend to waterlog, but with an Air-Trol such seems history.

I hate to be obtuse but if draining to check the air pressure IS routine, wouldn't it be easier (even better on the system) to use a plain tank and Air-Trol?

If such is NOT routine (my suspicion) then I guess you just wait until the tank looses its charge, waterlogs and system water pressure starts going bonko?

ed broderick_2

Expansion Tanks & Air

When cold, is the pressure in the tank (diaphram)always 12 lbs.? I checked the pressure with a good tire gauge only to find about 10lbs. I attempted to pump air into the bladder but had some resistance. Is it better to add air with the tank disconnected? I have a closed system using 30% Cryotac anti-freeze. All answers appreciated. Ed

Alan(CaliforniaRadiant)Forbes

X-tank

Before charging your x-tank, make sure the system side pressure is down to zero, otherwise you will get incorrect readings.

The air charge on your x-tank should be equal to the fill pressure on the hot water system, normally 12-15 psi for a 1 or 2-story building.

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Unknown

If the system pressure is below tank pressure, in reality, (rather than believing two different gauges) the bladder and air are occupying the whole tank space. The air charge is believeable from a reading at the tank valve. I never actually drained anything, I just cracked a drain valve for a few drips to ensure that the tank wasn't pushing back (as the pressure gauge drops fast to below the air charge pressure). If the pressure stays high, the tank is pushing back on the water and the bladder is NOT fully extended.

If you put air in the tank and the boiler pressure goes up with it, there is a problem.

My point is that very little water needs to be removed to check a tank, unless the tank itself has water in it.

Charge it to 12 PSI with the system water at 12 psi. Then drip some water out of a drain valve. If the tank pressure drops with the system pressure, do it again. At some point, the bladder will push the water out of the tank and the pressure reading will hold. If the tank is good, still, that is. Removing this water is nessesary, as the bladder tank needs to be full of air at 12 psi.

Noel

Alan(CaliforniaRadiant)Forbes

X-tank

Ideally, you install a ball valve at your x-tank connection so you don't have to drain your system each time.

As far as the charge on diaphragm x-tanks, it should hold for many years unless something is wrong.

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Mike T., Swampeast MO

Thanks

Glad there's a "better way"! I just work on the old ones with plain tanks...

Unknown

It has no diffusion barrier

For the same reason you need an oxygen diffusion barrier on pex tubing, tanks lose charge, slowly, constantly.

About 1 psi per year. It's verifiable, check a few. Let us know what you find on recently installed tanks.

Noel