Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

How to control radiators in a 1 pipe hot water system

I have a hot water system originally installed around 1955. It is a 1 pipe system with Venturi tees. I am tring to figure out how to cool down the radiators in the front of the loops. I have been told to use TRV's but now am told they will not work on my system due to the Venturi tees.I have 2 loops with 1 1/4" mains that tee from a 2" main. There are 15 radiators on one loop and 13 on the other. There are about 4 radiators on the front of the first loop that make the rooms to hot. Any suggestions?



  • Paul PolletsPaul Pollets Member Posts: 3,022

    Without re-piping the radiators to either a reverse-return or supply- return, you won't be able to add TRV's. Re-piping in heating season is not the best idea.

    You can control the output by setting the heating curve on the boiler correctly, but will not be able to fine tune on a room by room basis without TRV's. Monoflo one-pipe systems don't have much leeway. If the radiators were sized incorrectly, it's hard or impossible to balance the system.

    Re-piping is costly, and in a finished space creates inconvenience. If you want ultimate control you'll have to bite the bullet. If not, you'll have to see how your system responds by adjusting the heating curve.
  • jumperjumper Member Posts: 1,001
    enclose radiators

    Greening Steam has a section on this subject. It applies to hot water as well as steam.

    If you use louvres you can adjust each room whenever you like.
  • CanecreekCanecreek Member Posts: 21
    edited November 2013
    Radiator enclosures

    Excelent! I was already thinking if I had to i could partially block the radiators that were running too hot. I am a very accomplished cabinet maker so with the technical info I have seen I can make covers that will reduce the output of the affected radiators while not interfering with system flow. I will mockup a few designs then make some really nice furniture pieces from the one that works the best. I will post pics of the final product.

    Thanks again guys.

  • jumperjumper Member Posts: 1,001
    consider carefully

    Keep in mind that you can increase output of a radiator with appropriate enclosure.

    If you haven't done so already, get ahold of Greening Steam.
  • CanecreekCanecreek Member Posts: 21
    Radiator covers

    Already been there. I am working on a design with adjustable metal shutters that will take the radiator in either direction. Proper sizing, some properly placed reflective insulation, and possibly a low speed air circulator may be involved. I will be experimenting with a few design mock ups measuring supply and return temps to check performance. I would like to be able to predict the output with a given shutter adjustment. I hope to avoid an air circulator because of the value of low or no air movement has on the air quality but it may be required to improve output. I will post pics when I have results. If I am successful I will share design dimminsions and specs.

This discussion has been closed.


It looks like you're new here. If you want to get involved, click one of these buttons!