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Want suggestions for best practices piping to potable expansion tank

I've got an Amtrol potable expansion tank installed circa 2001, when we had the lead service replaced and required back flow preventers installed. I suspect the potable tank has failed internally - it's suspended from threaded tee in 3/4" sweated copper running across ceiling as cold supply to water heater, and it sounds 'full' when I thump it. The water heater TPRV has burped and reseated a couple times - so something's clearly amiss. I plan to check my city water pressure with a gauge, shut down water heater, shut off incoming water supply, drop and drain the potable tank, check and recharge to same as city water pressure? slightly higher? - then reinstall if I don't hear hissing through a blown diaphragm, and replace if I suspect a problem. I know it's a heavy wet mess to take down an expansion tank, and I'm thinking of adding isolation valve between tank and cold water supply - then wondered if one valve is enough, or if I want one to leave on the water line, and another on the tank, and maybe a third on a bleeder tee.... am I overthinking this, or do any of you have an favored clever arrangement that makes servicing potable expansion tanks less of a dripping pouring nuisance?


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited November 2015
    Yes tank pressure same as water pressure.
    Use this valve at the exp tank

    There was an error rendering this rich post.

  • Bob Vennerbeck
    Bob Vennerbeck Member Posts: 105
    Hatteras guy: yes, but at least one valve would be a d...n sight better that what I've got now, and once I start shopping.....

    STEVEusaPA: thanks for the link - looks great for hydronics with make-up inlet right at point of no pressure change, but clearly states not for potable use.

    So I'm going to swap out my waterlogged-bladder-busted Amtrol ST-12 for a new one, and install a ball valve between the new tank and the existing tee for the NEXT time - and hope that's all that's making the water heater burp. Pretty sure the ST-12 wasn't pumped up to match Providence Water Supply Board delivery pressure when I installed it, because I wasn't that smart fourteen years ago, and where were you guys when I needed you then?
    JUGHNE Member Posts: 11,077
    If you depress the Schrader valve and get more than a touch of water out of it, then a new one is in your future. If when the system is drained and after you remove the tank and it weight about 20 pounds, it is done also.