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DHW - Airlock or something else?

Have a 30 gal domestic hot water tank fed from my home furnace. This season I keep running out of hot water. When I investigate it seems the taco-007 Circe that’s right in front of the heater intake is airlocked. The motor itself feels very hot and i have hot pipe on furnace side and cold on tank side. What I end up doing is opening a drain that is on the return pipe from the tank to the boiler. Sometimes I need to play around with things like shutting the valve after the drain that goes into the boiler.

This doesn’t happen on any of my other 7 (yes 7 zones!) taco circs. I do have some air bleed mechanism that I can hear release air. I am tempted to get a replacement cartridge for the circulator. But someone told me the coil is bad and I should just get a regular gas fired water heater like everyone else.

Any suggestions from people who know this type of system?


  • kcopp
    kcopp Member Posts: 4,443
    You may have a bad circulator.
  • hot_rod
    hot_rod Member Posts: 22,258
    Does the pipe downstream a foot or so get hot? If not the circ is bad, locked, or airbound.

    Purge first if you can. if it has isolation valves you may need to pull and check if it is stuck or fried.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Zman
    Zman Member Posts: 7,573
    You have an indirect water heating system. I would never trade that for a stand alone hot water heater. You likely have a bad circulator. 007's are inexpensive. Just replace the whole unit.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • drosner
    drosner Member Posts: 45
    Thanks for the help! 007 is 100 bucks and if the old one still works then I have a backup for another time. Will try that out.

    I guess I was wondering if a 10 year old indirect water heater would be near end of life? Is there any kind of maintenance on a unit like this?
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,335
    Hello, As for tank upkeep, it depends on what sort of tank you have. If it's glass lined, there will be an anode to check and with either glass lined or stainless, there should be a relief valve to test. The condition of the anode rod, (if there is one) will let you know how the tank is doing. Ideally you'll find six inches of bare core wire on the anode and this is the right time to replace it.

    Yours, Larry