Kentucky Air vent on pressurized loop field?

Discussion in 'Maintenance and Troubleshooting' started by JeffM, Mar 18, 2015.

  1. JeffM

    JeffM New Member

    After installing a new flow center (thanks to the help of members here!) and purging air out of the system, I still notice a slight gurgling sound of air in the pumps. I notice when I hear the sound that the system pressure drops a bit so I'm pretty sure it is caused by air moving through the pumps. Not bad at all, I'm just hyper-focused on the system after replacing the flow center!

    I know many closed loop boiler systems, as well as geothermal applications, use an air vent such as this one:

    2 questions:
    1. Would there be any reason not to install an air vent? I realize they can become clogged or fail over time, but is there any technical reason why I would regret installing one?
    2. If it's ok to install, the highest point in my system is where the hose comes out of the top of my flow center. The hoses come out of the top of the flow center and then drop 18" or so to the bottom of the Waterfurnace unit. I'm thinking of installing a 6" tall pipe out of the top of the flow center (1" lines) with an elbow and a 1/8" fitting for the air vent. The air vent would then be at the highest point in the system, just above the pump bringing water from the loop field. I'll probably use CPVC.

    If I'm about to step off the curb in front of a bus I hope somebody can warn me! Any advice would be appreciated. Jeff
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I would point you towards an air separator over an air vent. And if you're going that route, you'll want to have makeup water and an expansion tank involved as well.
  3. JeffM

    JeffM New Member

    Thanks, Chris. Are you saying that if I install an air separator or air vent that makeup water and an expansion tank are necessary due to that device? Or are you saying that as long as I have the lines open and am going to the trouble to install an air vent/separator I might as well add an expansion tank and makeup water also?
  4. dgbair

    dgbair Just a hobby Forum Leader

  5. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Yes, air vents will lose water, so makeup is required unless you want to deal with an annual hassle.

    The expansion tank (and likely a pressure reducing valve and dual check valve) all now have a roll to play now that makeup water is involved.

    Am I recommending you do this? Not really. I guess you could just install an air vent with a shutoff and just open it occasionally when required.

    But, to do it properly...

    And, thus, non-pressurized was invented:)
  6. JeffM

    JeffM New Member

    Thanks, Chris and dgbair. I appreciate the explanations and advice. Maybe I should leave well enough alone. The system is 20 years old and it seems to be running as good as ever. I might be wasting time and effort trying to "improve it"!
  7. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I vote yes to the air eliminator, make up water. back flow preventor PRV and expansion tank. You could craft up an assembly and hose to and from the machines. I would install the assembly with service ball valves in the side of the loop the pumps back to the yard so that you are pumping away from the expansion tank that then becomes the point of no pressure change for that pump.

    While in plumber mode add a boiler drain to sample loop fluid. I do not think your plan is over improving the neighbor hood. If any thing it will make the eventual replacement a much easier job.

    Besides what you are thinking I add thermometer wells and pressure gauges.

  8. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    I would add that in your situation I would add a air separator after a shut off valve. This would allow your system to bleed air until final purge is reached. At that point you could shut the valve and boost the pressure via a needle valve in the PT port and life is good with no annual maintenance.
  9. ACES-Energy

    ACES-Energy Member Industry Professional Forum Leader

    Just be careful when you re-pressurize via a needle and the PT port. I have seen some DYI do this, but they hook it to a hose and open it up before purging the air out of the hose, and that gets pushed into the loop, now introducing more air...
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I have seen that more than once. LOL.
  11. Eric Mitchell

    Eric Mitchell New Member

    Sorry to hijack your thread, but I recently purchased a house with a geothermal system. Being a complete idiot on the unit, and after a quote to flush the system that was flushed a few years ago, I found this forum and a wealth of information. Thanks to all of you.

    First I have a seven loop system and one loop is closed (leaking I was told), but there are two ball valves into the header pipes I can plumb into. I have no idea on the length or depth of the loops, and the original owner moved out of state, so I don't have contact with them.

    The hvac contractor wants $1250 to flush the system and perform PM. There is a slight gurgling sound. Is that price reasonable? My loops don't have an air seperator, don't have an expansion tank, and of course don't have any makeup water.

    Should I plumb all of those components in, and let the seperator work, and if so, what size expansion tank?
    Also since I am admittedly an idiot, which side do I plumb everything to, the entry or exiting loop (which is which btw, two manifolds approximately 1 foot higher than the other).

    As for thermometers and pressure gauges, what and where on my loops?

    It's a WF Envision circa 2010, 2 ton unit, if that helps.
    Thanks in advance,
  12. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    One wants to pump away from and expansion tank.

    I'll drive up from Cleveland for that kind of money and help you plumb in the new stuff.

    I do not think I would bother replacing the leak if the system does it's job.

  13. Eric Mitchell

    Eric Mitchell New Member

    Sorry, I wasn't clear, the $1250 is to just flush the air out then perform maintenance. I was asking if adding the air seperator would do the same? If so, where do I plumb in the air seperator? One for each loop?
    Thank you,
    Last edited: Aug 26, 2015
  14. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    I think loops should be plumbed just like any wet system, which includes air removal and make up water. I put air eliminators in the high point of the system. The tank should be on the suction side of the pump.

  15. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Why don't you just get a non pressurized flow center and call it a day. Easy to install. They are cheaper than $1250 for flushing. BTW, with a good flush card, it should take them a couple hours to flush the system. Are you headered inside or outside?
  16. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Just as a side note. Yesterday I replaced a circ pump on a closed system and flush and purged the unit and the field in 1 hour. If nothing else get a quote from someone else in your area. Or call Mark.
    Mark Custis likes this.
  17. Eric Mitchell

    Eric Mitchell New Member

    My headers are inside, and I will look into the flow center.
  18. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    When they are inside, a non pressurized is specifically great, assuming you can shut off each circuit. That way the flow center can purge the air out of each circuit one by one. Chances are that gases will participate out again, and you need to pay again for purging. A non pressurized flow center will not undergo pressure fluctuations, thus much less gases participating out, and even if they do, will be purged out by the canister.
    Last edited: Aug 27, 2015
  19. Sino King

    Sino King New Member

    If the air purge valve was not mounted at its right position, it does not work. The right position is at the water running down elbow.
    For further information please contact

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