Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Backflow Preventer to a HW Boiler

RobLund Member Posts: 10
I recently changed out a vent valve on one of the HW radiators. I had to drain part of he system. I turned off the valves on both sides of the BFP and vented the system. After changing the valve I turned the valves back on and vented the system to the highest point, and filled the system. Now the bfp is leaking. Is there an easy remedy?


  • dopey27177
    dopey27177 Member Posts: 885
    The BFP may have dirt under check valve seat. Try draining some water out of the system and refill the boiler. Typically a BFP dumps water when the pressure in the boiler and heating system is greater than the pressure on the house side of the domestic water supply.

  • RobLund
    RobLund Member Posts: 10
    I will give that a try. I find it interesting that is the cause as there was virtually no flow when taking changing out the vent valve. It makes sense but kind of hard to fathom.
  • RobLund
    RobLund Member Posts: 10
    The boiler needs to be completely drained? That would be draing the entire system.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,036
    If you're draining the boiler, and you have a LWCO, put a ball valve upstream of the WF/BF and one right after. I don't like leaving the water feed open all the time. Check the pressure weekly (if no change in pressure). If you have a leak it will keep feeding.

    There was an error rendering this rich post.

    EBEBRATT-Ed Member Posts: 13,331

    Make sure the backflow preventer is on the upstream side of your PRV. If not they will act funny and cause problems