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Indirect tank expansion?

BoattailBu Member Posts: 12
edited March 2015 in Domestic Hot Water
Got a call today because the PRV on a Triangle Tube indirect tank was venting. Just for the heck of it, I pushed the valve down on the high vent to ensure there was no air there and there wasn't. It ended up being the expansion tank which I changed. When I opened the valves to return the system to operation, I heard the tank "creak" as if it expanded a bit. I don't have too much experience with indirect tanks so I didn't think much about it.

Toward the end of the day, I got a call back because the high vent was leaking water. I went back and prepared to change the vent so I closed both supply and return valves and drained off a little water. Turns out, I didn't have the correct high vent on my truck so I opened both valves again.

When I did, I very clearly saw the high vent move 1/4" to 3/8" and heard the "creak" again. Just to be sure, I repeated the process and confirmed the movement.

I'm no expert, but that doesn't seem right. I'll let the experts tell me what I missed. :s



  • Abracadabra
    Abracadabra Member Posts: 1,948
    what's the pressure of the water at? you sure PRV is working?
  • Jamie Hall
    Jamie Hall Member Posts: 23,455
    Are there any check valves on the system between the supply (cold) and the indirect? If there are, there should be an expansion tank in there on the hot water side. Could it be waterlogged?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BoattailBu
    BoattailBu Member Posts: 12
    I set the boiler pressure to 20psi. I was close to 25 when I arrived but the homeowner said that was the "normal" pressure.
    The PRV vented and then shut off so I feel that it is work OK.
  • BoattailBu
    BoattailBu Member Posts: 12

    Are there any check valves on the system between the supply (cold) and the indirect? If there are, there should be an expansion tank in there on the hot water side. Could it be waterlogged?

    There is an expansion tank for both the boiler and the DHW. The boiler one is fine and I replaced the DHW tank.

    I believe there is a backflow preventer on the domestic water supply.
  • Robert O'Connor_12
    Robert O'Connor_12 Member Posts: 728
    Maybe the tank/coil inside failed and it's bleeding city pressure into hydronic side
  • Zman
    Zman Member Posts: 7,579
    The tank within a tank design can make some funny noises. That much movement is a bit odd. It is important to fill the inner tank first when installing as the metal between the 2 tanks is thin and can be easily damaged.
    If I were guessing, it sounds like either the inner tank has been damaged (probably on the original installation) or the house pressure is really high.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • BoattailBu
    BoattailBu Member Posts: 12
    I was thinking it might be the coil leaking and city water was feeding the boiler but the system is allegedly only 8 years old and I wouldn't expect that on a fairly new system.

    While we are on the subject, does anyone have a quick and reliable method to determine if this is in fact the problem?
  • SWEI
    SWEI Member Posts: 7,356
    Turn off the auto-feeder if there is one. Drain some water out of the boiler and confirm that the pressure gauge drops. Note the pressure and wait a day or so to and see if the pressure rises.
  • Don_197
    Don_197 Member Posts: 184
    In our area, the manufacturers rep told me that those tanks will handle 75psi on the domestic side, and not a pound over......just thought I'd mention that. On the other hand, I have seen movement like this on Smart tanks ever since I started using them 6 years ago. there are some kind of flexible connectors from the shell to the hot and cold inlet on the inner tank, and I kind of visualize those connectors having to "center" themselves or something like that upon startup (maybe another reason why you are supposed to fill the inner tank first?) I have never once had a leaker, or a low output one, or any trouble at all with the Smart series......I Love em! The recovery rates are unbeatable IMHO.
  • Jimbo_5
    Jimbo_5 Member Posts: 218
    I had a TT Smart 40, installed in 2008, and in the beginning it was fine, worked great, no noises or venting issues. Then last year I noticed it would randomly make popping sounds as if expanding & contracting, and moving slightly. Yet no one was using the hot water and the Solo 110 was not fired to heat the tank, nor the house. I found this very strange. But since it was working, no visable leaks, so I disregarded it.
    Well, just before Thanksgiving it showed its true colors, rusty streaks running down the sides emanating from under the top cover. Why? Totally unknown. Upon installing the new tank I did notice several new twists. A new style air vent, to be kept "closed," the fact that they furnished a tube of "special" pipe dope to be used on all tank connections, and a notice NOT to use Teflon tape on any tank connections. It also seemed as though the tank to boiler threaded outlets were moved slightly too.
    This one is not making any noises nor moving, yet anyways. Who knows. TT made good. But GPS took well over 2 months to send me a check for for what TT had credited them.

    Now THAT really pissed me off. Fortunately for me it was installed in a relative's house, rather than a customer, so I simply swapped them out rather than have a customer screaming about waiting 2 months for their $$$$ to be returned.