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Adding rads to existing branch

metrosilo Member Posts: 16
I'm installing a new hot water system in an old building. On the plans, it shows every single rad having its own supply and return off the main loop. There is one section of building where the piping is going to be quite difficult and I wanted to add a tee off of a branch line to connect another rad. 
For example, there is a 2" main and it shows 2 , 3/4" branches off the main to 2 rads. Could I just have one 3/4" branch from the main and then add a 3/4" tee off that to the 2nd rad?
Then do the same for the returns. 

Hope that makes sense. 


  • Jamie Hall
    Jamie Hall Member Posts: 18,923
    How well that would work would depend very much on the lengths, but in any case you might run into some real balancing troubles. that said, you'd be much better off to use a one inch branch off the main, and split that into two 3/4 inch branches to the radiators, and likewise for the returns.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • metrosilo
    metrosilo Member Posts: 16
    One rad is about 8-10 ft from main and the other is about 20 ft. Both rads will have balancing valves on them. I was thinking of up sizing to 1". 
    Do you think that would work?
    EBEBRATT-Ed Member Posts: 11,989

    You need to know the water flow that you need. You find the water flow from the BTU rating of the radiators at the water temp your using.

    3/4" pipe or tubing will flow a maximum of 4 gpm. 1" will do 8 gpm