exspansion tanks

jaybee

When do annual maint. on a system with the older style exspansion tanks do u drain all the water thats ion the tank or do u drain out most of it?

Brad White_2

Ideally

there should be no loss of water to the system and hence no need to drain...
Back to reality.

If you find yourself doing this annual ritual, there is a water leak somewhere and the air charge in the tank is being reabsorbed and lost. Classically the ritual is to vent radiators that become airbound (which reintroduces water via the fill valve). Source of said air is only present in the expansion tank in a normal older system. When the air is reabsorbed and vented, it is displaced by new (oxygenated) water and the "cushion" of air is lost. The pressure relief valve (and your spouse) start to weep. And you are compelled to drain the tank and re-start the cycle.

Can I make a suggestion? Install one or more diaphragm type sealed expansion tanks. If an older large volume system, base the tank size on volume not "btu's". A #30 tank, the equivalent of a 30 gallon old style tank, will run you about $30 per.

Once done and vented (connected to the suction side of the pump thank you, and with a Spirovent air separator if you are feeling good about yourself) you ought to spend the time you spent draining and venting on other more joyous pursuits.

Big Ed

Old Compression tank

The old tanks in the basement ceilings need to be fully drained about once a year unless they sport a B&G airtrol . The airtrol prevents the loss of trapped air ,thus no draining needed.....

Also if the system(boiler and radiation) is lower then the tank you also don't need to drain the tank. Unless someone installed a auto vent....

Ken D.

Exp. tank

As a rule I do not drain the tank as part of maintenance unless I see a problem or it has been a problem. I prefer to keep the addition of fresh water to a minumum.If the system has been piped properly, you will never have to drain the tank. I haven't had to drain my tank in 16 years.