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How to repipe to fix these rads?

sixplex Member Posts: 89
edited September 2020 in THE MAIN WALL
So again, this is over 60 years old. Is this piped completely wrong and if so how to best repipe.
This radiator gets hot but the return pipe is barely warm.
Air is not an issue for this one 100%.
On the diagram X marks the monoflow tees which are about 2 feet apart.

The real problem is this radiator which has never worked. I don't know how it connects to the loop but i'm assuming the same way as the one above because the pipe connected to the top (right one) seems to also be the supply because it is somewhat warm.


  • Danny Scully
    Danny Scully Member Posts: 1,429
    I guess one question to ask is: did it ever work? 
  • sixplex
    sixplex Member Posts: 89
    No one knows. But not with the current boiler setup which is 15+ years. Maybe original circular was was more powerful and the system had fewer restrictions.
    EBEBRATT-Ed Member Posts: 15,829
    Does the radiator have two monoflow tees on on the supply and one on the return as your sketch shows?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    Downflow connected radiators in a monoflow system can be very hard to purge of all air.

    There was an error rendering this rich post.

  • sixplex
    sixplex Member Posts: 89
    edited September 2020

    Does the radiator have two monoflow tees on on the supply and one on the return as your sketch shows?

    yes! and the arrow is pointing in the same direction on both, according to the FAQ they should be pointing in different directions
  • ratio
    ratio Member Posts: 3,696
    If the tees are actually the same (& not something like a 'supply' tee & a 'return' tee, where the arrows are supposed to point in the same direction), that would certainly be an issue. With both the arrows pointing the same direction, both tees will try and force water into the bull.
  • neilc
    neilc Member Posts: 2,715
    doesn't that Tee label say bottom outlet on it,
    and is it pointing up, instead?
    known to beat dead horses
  • JohnNY
    JohnNY Member Posts: 3,244
    In your diagram, there is an elbow between the supply and return tees. That fitting may be the equivalent of 5' of pipe's worth of restriction. I can't make the connection right now but I'm guessing that is having a negative impact on your flow.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • retiredguy
    retiredguy Member Posts: 929
    See if you can find any of the old engineering drawings to find out what circ pump was used on that old system. A lot of these Monoflow systems used high velocity pumps or a pump with a higher head than those used on other systems to move the water. If the system is very old, I would suspect that it worked until the newer boiler was installed. These old systems worked well until someone changes something.