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Thread: Monoflow heating system/ Air in system

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  1. #1

    Default Monoflow heating system/ Air in system

    My house has monoflow hot water heat. Since buying the house we have made a couple changes, nothing major to heating system. The problem I have is that I cannot get the air out of the system. I have gotten it to a point that you could not hear any air flowing in the pipes but then a day or two later its back. My wife thinks I am nuts, spending countless hours bleeding and searching for air/water leaks to eliminate this problem.

    A friend of mine said that this is a common problem with this type of system, and if I wanted to keep it this way that I need to make a couple changes. These being to install an "air scoop" ( to remove the air in the main loop)and a new expansion tank (current one is the original bladderless type).

    Any insight and advise would be appreciated. Thanks, Ed

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default air

    Air in the system has nothing to do with it being a MonoFlo system. And all systems need some type of air removal device, although many MF systems had a BoilerTrol which separated it at the boiler. A new expansion tank will also not do anything to cure it. The most likely source of ongoing air problems is a bad seal at the pump which allows air to enter but not water to leak out.

  3. #3

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    I installed new gaskets on the circulator pump this year and it has not helped. Other than the bleeder valves on the baseboad units there is no other way to let air out. Given this, should I install a "bleeder valve" in the loop pipe? and if so what is the correct location?
    Thanks Ed

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    Did you install an air scoop? One brand is Spirovent...there are others. All closed systems need something. I'd replace the expansion tank with a bladder type. They last awhile, but put a shutoff valve to make changing it easier when the time comes the next time.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5

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    On which side of the boiler would the air scoop and expansion tank be installed?

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default boiler

    At the boiler's outlet to the radiation. Gaskets on the pump's flange have nothing to do with air entering the system. If they were the problem, water would be leaking OUT. The pump's shaft seal is in a low pressure area, which is why it can move water, but it is also where air can be sucked in if the seal is going bad.

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