Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

air burst on indirect water htr

Weezbo Member Posts: 6,232
that there is excess cavitation from the water source .

either due to draw down times or a devise or fitting in line.

that is ,if the check valve and sized expansion tank are in the picture. and the water temp of the hot water is not going into over heating condition in which case are you Sure you dont want an anti scald
devise to protect your customer at this time?


  • Dave_98
    Dave_98 Member Posts: 9
    air burst on indirect water htr

    We installed a Buderus G115/5 oil-fired boiler with a Buderus ST150/2 indirect water heater. We had removed a older oil-fired boiler with tankless coil. The customer has stated that whenever they turn on the hot water, they recieve small bursts of air in the beginning of using the hot water. Once they run it a while it seems ok, but after a while the will alwys get this happening. Has anyone one else ran into this? I had talked to my Buderus Rep and he felt it is a problem with the well pump, but.......this person is a very good friend of mine ( I know, dont work for friends) and he stated that it did not do this before, which I believe him. Any ideas on this? thanks
  • Paul Rohrs_4
    Paul Rohrs_4 Member Posts: 466
    Several things I would look for

    Is there an old gate valve that is partially opened/closed? I have seen this culprit not let adequate pressure/flow cause a blast of air.

    Is there a water softener? A brine-draw float assembly stuck open will also let air back into the system.

    There might be other simple answers, but these two have plagued me before.


  • Weezbo
    Weezbo Member Posts: 6,232
    Dave, are we liking the idea of :St-12's ,check on the cold,

    anti scald devise and domestic HW recirc in that lash up?

  • Dave_98
    Dave_98 Member Posts: 9

    there is not a antiscald device and the recirc loop is not used
  • Tim Weaver
    Tim Weaver Member Posts: 49
    buderus tank

    Another problem to look at is the magnesuim anode rod in the tank, sometimes due to water conditions, the water can attack the anode very quickly causing gas to form at the top of the tank and when the tap is opened the homeowner gets these bursts of air. Also, sometimes associated with this issue there can be a rotten egg smell especially if the tank is on a well system. I work for a indirect tank mfg here in Vancouver BC, and we have run across this problem from time to time. We have found that making sure the tank is well grounded to prevent electrolysis seems to take care of the problem. Hope this helps

    Tim Weaver
  • Dave_98
    Dave_98 Member Posts: 9

    tank is brand new, only been in roughly 2 weeks. This may have been a problem before and they just never realized it. I just have to find out what is causing it. I know sometimes if you have a faulty bladder in your well tank, that you can have probles simular to this. The house does have a well water system.
  • Tim Weaver
    Tim Weaver Member Posts: 49

    Dave, I know how frusrating it can be, but I can tell you that we have had similar situations, 2-3 weeks after installation and the air bursts began. We encouraged the use of di-lectric unions and checking of the anode every six months to get a read on how quickly the anode was being attacked and we were very surprised to see how quickly it had taken place, the homeowner is replacing the anode every 6-8 months. Yikes, not nice, but with his water condition it was needed.

    Tim Weaver
  • steve_29
    steve_29 Member Posts: 185

    I'll bet it's a jet pump not a submersible
  • ScottMP
    ScottMP Member Posts: 5,884
    Tim said it best

    I think your on the money with this one. Check the condition of the anode rod, lokk for white and milky.

    Check with Buderus if they make a different anode. I've never had the problem with there tank but we don't do so many and not many wells.

    My bet is the anode

  • Larry Weingarten
    Larry Weingarten Member Posts: 3,286
    I'll add...

    ... that it's not too hard to test. Remove the anode and put a plug in the port for two or three days and see if the gassing stops. If so, a less active anode, like the aluminum/zinc anode used for odor could be the fix.

    Yours, Larry
  • Joe@buderus_2
    Joe@buderus_2 Member Posts: 302
    Anode Rod

    It sounds like it might be the anode rod being attacked. Does the air burst occur after no hot water use? We now offer an aluminum anode rod for most tanks. Please contact me if there are any questions.
  • Mitch_5
    Mitch_5 Member Posts: 102
    Did you have the water tested

    you may need to treat it after it comes in and before the heater.

    Mitch S.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Guy Woollard
    Guy Woollard Member Posts: 82
    Too simple?

    Perhaps there has always been a small amount of suspended air in the water supply; With a tankless coil, there was no place for any appreciable volume to accumulate. It was there, just not in a mass. The top of a storage tank would capture and accumulate the small bubbles, making a larger burst of air. If I am not mistaken, the DHW piping comes off the top of that tank as well, allowing that accumulated air to eventually rise within the system. Is this happening in primarily one outlet (the first), or is it house wide?

  • Dave_98
    Dave_98 Member Posts: 9
    air burst

    Problem is pretty much house wide, there is absolutly no smell at all...i was there last week and there was a small amount that came out of the hot when i used it. We will keep monitiring this, installing a plug to replace the anode may be a way to check if it may be causing this.
  • Joe Brix
    Joe Brix Member Posts: 626
    check the well pump/press tank

    I bet ya air is moving from that tank to the indirect.
This discussion has been closed.