expansion tank replacement proceedure?

[peabbles]

Can someone walk me through the proceedure of replacing an expansion tank.

This is an inline tank with the air valve at the bottom. Pre-charged to 12psi.

Is it as simple and shutting off the water/boiler, unscrewing and screwing the new one on?

Thanks,

Jim

[jadnashua]

Shut off the fresh water makeup valve, too (if you have one). Relieve the pressure in the system, then unscrew the old one (it will likely be heavy since you're probably replacing it for a failed bladder - it is full of water), install the new one (use pipe dope and/or teflon tape), repressurize the system by turning on the make up valve and you are nearly done. If you have an auto air extraction valve, you probably are done, if not, then you may have to purge some air. My unprofessional experience.

[peabbles]

replaced the expansion tank last night. No more water coming out the PRV. Thanks for the help.

[jadnashua]

One of the pros will probably comment, but you may want to put some more air in the tank, as the bladder will be stretched more than it needs to be if it is only at the 12 pounds. To get the pressure right, you need to relieve the pressure first, then check the pressure, add as necessary. I thought you were putting it in a boiler circuit, and 12 pounds is right for it. On a house potable water system, I think it needs to be higher. Saw somewhere else on here that it should be higher than your normal pressure.

[peabbles]

it is in a boiler circuit. Should the pre charged 12psi be enough. It is only for baseboard heat not for potable water.