Selecting right expansion tank

I have a boiler from around 1968. The pressure is building up and releasing so I figure that I need a new expansion tank. Reading through this forum, I see that current expansion tanks last around 6 to 8 years. The expansion tank that is on my boiler says it is from 3/68 (see pic). The only markings on the tank are 8 GAL. and 3/68. I am wondering if that is possible or am I looking at something different? and will replacing it with a #60 Extrol Expansion Tank (7.6 Gallon Volume) be the correct replacement? Thank you for any info!

 

Welcome to the forums.

I'm not the boiler pro but some observations.

I believe that is a bladder less tank. You would recharge that tank by shutting off the supply to it, removing the side plug, draining the water out until it's at the plug level, replace the plug and restore water pressure. Old school technology. Tanks today have a rubber bladder that keeps the air (charge) and water separate. I would definitely replace it. I don't know if the one you choose is the correct one. The boiler crew will be by and should offer some help.

Be careful with that tank. It will be heavy if it's full of water.

 

No need to replace that exp tank. It just needs maintenance.

we would need more pics well lit all around boiler.

You need to turn off water supply to boiler and drain that tank. Then when the boiler gets refilled it will air charge the tank. That is whats causing your relief valve tripping most likely. Although your fill valve can be faulty also causing the high pressure.

If you did install a bladder type tank then you will need to add air vents to your system. So IMO keep what you have. You should have no air vents on that system.

 

Thanks Guys! I figured out it was a bladderless tank after thinking it over. I shut off the supply and drained as much as I could out of the tank and then opened up the side plug to drain the rest. Of course after refilling I believe the reduction valve is faulty, so I pressurized the system to 20 psi and shut off the supply valve. Everything is running perfect, I am just waiting for my replacement reduction valve and keeping a close eye on the pressure. I really appreciate the input. Thank you Pete and Mike.

 

You're welcome. Thanks for letting us know how you made out.

 

No air vents on the system? I thought that all hydronic (FHW) systems need air vents at the radiators.

A new bladder tank sized for your system will generally be smaller than the old non-bladder tank. The larger size of the non-bladder tank allowed for less precise instructions for recharging it, longer time between servicings and rechargings, and still getting excellent performance.