expansion tank

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mark123

Member
Jan 27, 2009
174
PEI, Canada
Are you supposed to add air pressure to a bladderless expansion tank? I recently heard a plumber on a radio show say to add 25-30 psi of air from a compressor. I thought you just let it fill with water to creat the air pressure inside it.
 
You have to add air. Fill your system, being cold put a little water in your expanshion tank. then fill tank with air till you reach your minimum operating pressure. usually 12 psi.
 
Now what about the auto vent on the boiler, after the system is bled and working fine, should the auto vents be tightened as not to let air out? The reason I ask these questions is my tanks becomes waterlogged about once a year, I added a second tank thinking I needed more volume and it is still getting waterlogged. Is it possible the air is dissolving into the water and then escaping out the auto vents? 2 X 15 gallon tanks
 
If there is air in your system, I think you want it to get out. I keep my auto vents closed (after the system was up & running for a while), but open them once in a while to let out any bits of air that might have accumulated there.

On your expansion tanks, I have a non-bladder tank on the floor. I don't think it's waterlogging, even though I was worried it might. I should try to check it I guess - haven't checked for a while. But I also run pretty lower pressures - like 12 psi tops when hot (drops to 6-8 when cold). Higher system pressure might lead to more waterlogging?
 
Why do you have your tank on the floor, I thought it should be above the boiler to collect any air?
 
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