Expansion tank replacement

aaplumber

I have an old hydronic system with radiators that has a leaking cushion type expansion tank. Can I replace it with a proper size pressurized type tank without an air separator fitting? Or should I try to find another cushion type replacement? In this case it's impractical to pipe in an air separator. Thanks.

kcopp

So do you have the old style tank that has no diaphragm? Those usually last forever.
If you want to convert to a diaphragm tank you can...what do you have for air removal? Many times that old style tank acted as air removal.
here is the chart to figure out the size....

http://www.amtrol.com/support/extrol_res_sizing.html

aaplumber

Thanks. I replaced with a new old style tank. Interestingly I think the tank was leaking because of high pressure in the system, it caused the tank to swell at the seams.. The customer purchased the house about a year ago and it was vacant for several years. I assumed the tank froze at some point because of the bulges in the seams. After I replaced the tank and fired the system, I couldn't trip the relief valve! When I removed it , the outlet side was corroded completely closed! The owner said that the home inspection report said the pressure was too high in the boiler! The fill valve was "serviced" to correct the issue by another contractor. I think the boiler was running on house pressure of 75-psi cold! The high pressure swelled the tank at the seams and it began rusting there. It finally started leaking. It took a hammer and chisel against the seat of the old valve while in a vise to free it! The drip tube on the old relief was black iron. Lucky for the owner that the tank started leaking!