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Rusty expansion tank

CBRobCBRob Posts: 154Member
edited December 2019 in Domestic Hot Water
Hey guys. So one of the houses in the neighborhood I manage just had an expansion tank rust out on them. It's the first one I've seen go like this. It was full of rusty water. Failed at a little pinhole leak.
None of my other houses seem to have this issue.
Is there anything water quality wise I should be checking to see if it's corrosive? No water softener in the house.
Is there a more rust resistant expansion tank? Do I need something with a liner or a stainless steel?
Appreciate any info thank you.


  • hot_rodhot_rod Posts: 12,584Member
    How old is it? Tanks do fail from time to time. Is it sized properly?
    The pre-charge pressure needs to be checked and sometimes adjusted when you install them.
    Directions will be in the box or go online for sizing and installation info.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Larry WeingartenLarry Weingarten Posts: 1,677Member
    Hi, I've got a few thoughts and questions. Are you on a municipal system so you can get a water quality report? That would be useful info. What is the static water pressure? Is there a backflow preventer or some other regulator/check valve in the supply line to the house? I'm asking to see if there is really a need for the expansion tank. Is the tank required by the local code enforcement folks? Might the water treatment being used by the supplier be bad for the rubber in the X tank? See this:

    Yours, Larry
  • CBRobCBRob Posts: 154Member
    Thanks hot rod. I'm not exactly sure how old the tank is but probably about 10 years.
    The house pressure is about 65 psi city main is probably 85 but there is a pressure regulator by the water meter.
    I think it will come typically pre-charged at 45 psi so I should pump it up to 65, does that sound right.
    Is there anything I need to look for that could be causing this corrosion? Is there a better quality replacement tank that I can put in its place?
  • CBRobCBRob Posts: 154Member
    Good question Larry. It seems to be a redundant tank anyway. The house was recently retrofitted with a solar assisted under floor radiant heat.
    It's got a 50 gallon non-condensing water heater, and a storage tank for the solar heat system.
    There's a four gallon expansion tank on the domestic hot water, and then there's two gallon tank that was leaking that is part of the circulation loop running through the storage tank.

    Probably doesn't need two separate expansion tanks on one 50 gallon heater.
    The contractor that installed the solar system is not answering the phone now, and I just threaded in my pressure tester in the 3/4 inch hole just to cap it off and get this guy some hot water going again.
    I was about to order up a replacement expansion tank for him while we wait for a call from The solar heating contractor. I think I'll wait before I order up another tank. I bet we don't need one there.
    But it might be time to replace the other 4.4 gallon expansion tank that's on the domestic hot water. If one has rusted the other one might be right behind it.
    And I can call the water department and see if there's anything that could be causing corrosion. Those guys are easy to work with and I'm sure they have reports on hand
  • CBRobCBRob Posts: 154Member
    Here is a link to the town's water quality report. It's a PDF file and it's the one labeled MCB.
    We generally have some really good water up here, low on the parts per million.
    Pretty much at the very top of the water supply chain, we're getting it from 9,000 ft elevation
  • CBRobCBRob Posts: 154Member
    As far as quality goes? Is there much difference between Watts and amtrol?
    Any other players in the expansion tank game that I need to look up
  • hot_rodhot_rod Posts: 12,584Member
    I think all brands are comparable ,

    Zilmet is another brand and they offer stainless with NSF certification if you think you want a shinny tank :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • JUGHNEJUGHNE Posts: 6,533Member
    Even with a whole house exp tank, if there is a check valve on the supply to this unit then probably need a tank.
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