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DHW Indirect Air Elimination

ced48ced48 Member Posts: 383
All of the piping diagrams I have seen provide no air elimination provisions in their setups. Is this standard? I am having trouble with air in my DHW loop, should I install something, if so, where, and what?


  • SWEISWEI Member Posts: 7,356
    SMART indirects

    come with an air vent.  Both diagrams and instructions cover installation.
  • hot rodhot rod Member Posts: 7,068
    does the boiler have an air vent?

    most mod cons have a vent on the HX. As long as you get the "big air" at the fill and purge, the vent should find the rest and eliminate it.

    Got the expansion tank connection correct?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ced48ced48 Member Posts: 383
    HTP Superstor-

    maybe not so smart?
  • ced48ced48 Member Posts: 383
    Lochinvar Boiler

    I added a vent in a cross at the top for pressure release and LWCO-
  • icesailoricesailor Member Posts: 7,265
    Air Elimination in Indirect:

    Do you have enough pressure in your system? Do you have an accurate 12 to 16# pressure?

    I've never seen so much fuss over air elimination as I see here. Any system I ever worked on, once air was purged initially, that was the end of it.  Proper pressure will compress air into the water. Don't go by the pressure on the front of the boiler until you prove that it is accurate.

    I always put can vents on to shut people up but tightened down the caps tight so they couldn't suck air into the system.

    What are some of you doing wrong?
  • ced48ced48 Member Posts: 383
    So, Air in the DHW

    loop doesn't seem to be an issue very often, so no one adds any air elimination devices?

    My system seems to get air into the DHW loop when the heating loop works hard at higher temps, like last night's 5 degrees. The air seems get into the DHW loop and than takes days to work it's way out. I think maybe I need to add a scoop to the loop to take care of the air more efficiently. Any reason not to do this, or am I treating the symptoms, not the real problem?
  • icesailoricesailor Member Posts: 7,265
    Size:Broken records:

    What size is your expansion device (pressure tank, is it big enough, and is the system pressure high enough?

    Like just because you fast fill it to 16#, and don't adjust the pressure adjustment on the fill valve, doesn't mean that the system is running at 16#. And you have to adjust the tank pre-charge pressure to.

    I don't mean to sound like a broken record, but I used to turn on and off a ton of houses with all types of systems. In all my years of doing it, installs and services, I never EVER saw all these issues with air that I see here. Its like an epidemic. Do we need to call the CDC about it? It must be contagious
  • ced48ced48 Member Posts: 383
    I Did Notice

    the system pressure was on the low side this morning, 12 pounds or so- I'll boost it up to 16, and check the tanks pressure-Thank you for your help
  • Pughie1Pughie1 Member Posts: 116
    Air seperator

    If I might suggest - since you mentioned adding an air scoop. I would re pipe it with a microbubble air separator instead of a scoop. There are several on the market. They create a low pressure zone and along with high temperature will allow entrained air to come out of suspension and be removed from the system, a can vent cannot remove air in suspension.

    It's been my experience that once you initially purge the system and start circulation the separator will take care of the rest. Within one day in normal circumstances the system will be air free.

    Ice is right - if you know what you're doing - pipe um right, start um right and air becomes a no issue.

    John Pughe
  • hot rodhot rod Member Posts: 7,068
    what type of air eliminator

    do you have on the system. the fluid in the DHW indirect loop will at some point circulate through the boiler and heating loop. A few different causes of air problems.

    Air elimination device faulty or plugged, not installed properly, PONPC

    waterlogged expansion tank

    low static fill pressure

    entrained air not being removed

    restrictive valve or device in piping causing cavitation

    There is a lot of value in the modern type micro bubble type of air separators, they trap air and micro bubbles that just pass through scoop type vents. Money well spent.

    If the indirect creates a high spot in that piping, not a bad idea to add a float type air vent at the high point.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ced48ced48 Member Posts: 383
    Watts AS-MB

    on the sytsem-heating loop has no problems with air, quiet. I have had a rattle in the DHW circulator. I was able to get rid of it this morning by closing the isolation valve down enough to cause some disturbance, which shook whatever loose, I assume from the internal check valve. Rattle is gone, maybe it was causing some cavitation,we will see-
  • hot rodhot rod Member Posts: 7,068
    maybe pull the circ

    if you have good isolation, and check the check! I have see a few of them dislodge from their appropriate resting place and cause flow issues (noise)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • ced48ced48 Member Posts: 383
    Stupid Me-

    After reading icesailor's and hot rod's suggestions, it became obvious that I had screwed something up. Thinking about the fact that the condition got worse after higher operating temperatures, I keyed in on the expansion tank. It was brand new, and large enough, but what about it' s charge, had I checked it? NOT-Added about 12 pounds of air, and presto, all air noise was gone-I guess I assumed it had 12 pounds of air, it only had a couple of pounds, dumb, amateur, mistake. System pressure is now at around 16 pounds, tank has about the same charge, and all is quiet as a mouse. Again, thanks to icesaiior and hot rod for all your help.
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