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In-fllor heating - drain the system

Jake Member Posts: 2
If my floors do not warm up and the return leg is always cold (although the supply is hot), can it be due to the air in the system ??

If so , what is the best remedy ? Purge the system ? Am I right ?

Now ho do I purge the system ....Here is my plan - please, give your comments:

1. shutoff the hot water supply to the heated floors (I do have a valve that would allow me to isolate the floors)
2. shutoff the return leg of the floors

Basically after (1) and (2) my floors will be isolated from heater on both the supply and the return leg.

(3) Connect the hose to the vent on on the return leg and have the water drain.

(4) I also have a vent on the supply line. Should I drain through it as well ?

(5) When all set and done, the floor system will be dry ? I will connect it back to the boiler .

Your comments appreciated.


  • darin_2
    darin_2 Member Posts: 12

    Let's cut to the chase. You need to force the air out using pressure and flow. Ideally, there should be somewhere in the piping a boiler drain, a valve, and a boiler drain. Using a utility pump force fluid in one drain, through the system and into the same 5 gallon bucket the utility pump is drawing fluid from. When the bubbles stop, the air is gone. You have to be mindful of air elimination at the time of the install. If your not, you weave your own web. If you have manifolds in the house, with luck the same process will work there(are boiler drains present?).
  • hr
    hr Member Posts: 6,106
    It helps

    to be able to isolate loops and purge one loop at a time. You may not have enough volume to purge multiple loops at once. Especially if you are using the 12psi fill valve as your make up source.

    If you use a garden hose, be mindful of the pressure relief valve setting on the boiler or heat source. You will need to stay a few psi below that valve setting.

    If you can isolate the manifolds from the boiler, by all means use a high pressure to blast out the air. it can take a few minutes per loop. put the purge hose in a full 5 gallon bucket to see the air bubbles come through.

    hot rod

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