Hot water overflow

Discussion in 'Plumbers' Talk' started by Jonesy123, Jul 23, 2018.

  1. Jonesy123

    Jonesy123 New Member

    Hi guys, I’ve looked through threads but can’t get an answer to my issue so here’s the details.
    I have a zoned non-pressurized oil fired heating system, hot water, upstairs and downstairs heating. Each is controlled by a room stat and a cyclinder stat (mounted 1/3 up and set at 60deg) which I have just replaced with Honeywell stat.

    The issue is that after approx. 20 mins of the heating (hot water only) being on the pipes start rattling and the water is flowing out the overflow until I run off the hot water. The upstairs hall radiators are also really hot. I first thought the cyclinder stat was faulty but I checked when it happens and the cyclinder temp is only at 45-50deg(turning down until I hear click and then the hearing shuts off) and the motorised valve is also still open (light on) so it’s still on.

    Please help as I’m beat.
  2. chippie244

    chippie244 Super Member

    Check the t's and c's. No spamming.
    The Teach likes this.
  3. kiaora

    kiaora Guest

    Sounds like a circulation problem, may be just an air lock, in the primary flow and return, or maybe a faulty valve, you think it’s open but it’s not!

    May be pump?

    A plumber will figure it out I’m sure.

  4. rogerk101

    rogerk101 Screwfix Select

    It sounds to me like your pump is continuing to run on when all your valves are closed, and the water it is circulating has nowhere else to go than out the overflow.
    You demand heat for your hot water tank, so the hot water tank zone valve open and the pump starts. (The upstairs and downstairs zone valves are shut because the current ambient temperatures are higher than their respective thermostat settings.)
    Your hot water tank reaches its required temperature after about 20 minutes, so it shuts off the hot water tank zone valve. However, it's not turning off the pump. Your upstairs hall radiators may be the intended bypass for when all zone valves are closed, but maybe they have TRVs fitted, so they will heat up. They will only heat for a short while in this weather, but as soon as they're have heated enough, their TRVs turn off. Now the pumped hot water has nowhere to go except out the overflow.
    This may be a long-time existing problem that has always been there, but these hot weather conditions have only revealed it now. Are there any other differences in your lifestyle? (e.g. would you normally be away at this time of the year?)
    Has anything else changed?
  5. Dennisplamer

    Dennisplamer New Member

    Hot water flows from tank basically caused by corrosion, sediment build up inside the tank or valve may be defective.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice