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old rads

Beckster Member Posts: 1

I have an old house with cast iron rads. we recently did a reno and replaced some of the old pipes with flexible plastic. the rads that were changed to 3/4 flexible tubes do not heat up as well or not at all. It's not an air lock. Could it be because the flexible tubing is too narrow.




  • EddieG
    EddieG Member Posts: 150
    Need more info

    Do you have a gravity system? or do you have a circulator(s) at the boiler? Did you have a main pipe running around the perimeter of the house with tee's in it supplying the radiators? If so you probably had a Monoflow system. If this is the case, you are going to need a pro to evaluate and correct the issues you may have caused, without knowing.
  • Al Letellier_21
    Al Letellier_21 Member Posts: 402
    old rads

    If your old rads with piped with larger pipe, like 1 1/4" or so, and you went to PEX, chances are you pipe them just like they were....in and out the bottom of the rad??

    If so, the water is now moving faster and passing right through the bottom of the rad without giving off much heat. You have to slow the water down or consider piping in the top of the rad on the supply and out the bottom. Water always takes the path of least resistance and will run right through a rad when piped at the bottom only.
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