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Thread: Rads dont get hot with mono valves

  1. #1

    Default Rads dont get hot with mono valves

    I have added a few new rads to my home heating system and 3 of them don't get hot. These 3 rads have new mono type valves (which means the flow and return are together connecting to one side of the rad).

    Both flow and return pipes are hot going into the valve, but it seems the water just goes in the flow pipe and out the retrurn pipe without actually heating the rad.

    Could it be that the shop forgot to give me a short piece of plastic tube which forces the hot water some distance inside the rad? And without this tube the hot water doesnt get inside the rad? Because I remember fitting similar valves before, but they came with a short piece of tube, about 10 cm long.

  2. #2
    Consultant cwhyu2's Avatar
    Join Date
    Aug 2007
    Cincinnati OH


    Are there bleeder valves at the top of rad,if so you may have to bleed
    the rads of air.

  3. #3


    I have spent ages bleeding the 3 rads individually. While Im bleeding they do get hot , but when I finish, they just return to normal, almost cold.

    But my main question is: should this type of mono valve (Giacomini) come with a short piece of`plastic pipe to make the hot water actually get inside the rad? Thats the only thing I can think of because other mono valves I had installed before came with a short piece of plastic tube.

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default rads

    Without something to divert/direct the flow the water will just enter the radiator and then exit immediately out the return line.


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