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Discuss Cold water tank in loft overflowing in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Fireblade9

    Fireblade9 New Member

    hi this has us a bit baffled our heating systems is cold water tank and little f e tank in the loft immersion cylinder in airing cubard and boiler in kitchen
    The problem was the overflow to the cold tank keep dripping so I replaced the ballcock turned mains on watched it fill up and cut off nicely job done
    Next day noticed overflow dripping went in loft looked in cold tank ball valve under water so turned isolating valve on mains in ran a few taps so water level dropped left it isolated over night the next day the water level was right up again to the overflow
    The cold feed pipe from the bottom of the cold tank goes into bottom of cylinder now that pipe gets hot all the way back up to tank can even see in the tank swirling like it’s back filling with hot but run any hot tap and the cold feed pipe goes ice cold again for about a hour the heats back up
    Iv had two plumbers look and are not sure
    All taps are mixer type no taps or showers have been changed in last 4 years
    Any help or ideas much appreciated I apologise for long post just trying to give as much details
     
  2. Jim Goodenough

    Jim Goodenough Member

    Is your hot water hotter than usual?

    Is your heating system fully pumped? or gravity for hot water circuit and pumped for heating? If it's a gravity system your boiler thermostat could have failed. This will overheat the water.

    Alternatively do you use the immersion heater? Has it been left on by mistake (if it's on a high setting and left on it could be expanding your hot water excessively)?
     
  3. Ric2013

    Ric2013 Plumber

    If you have a hot water cylinder fed from that cold water cistern, the coil in the cylinder could be leaking. If so, the water from your heating system could be pushing into the coil from the small F&E and then passing through the leaking coil and up the cold feed into the cold water storage cistern.

    If the ballcock of the F & E is not dripping or the water level in the F & E is lower than the water level in the cold water storage cistern, then I'm probably wrong in the above paragraph.

    I like your approach to actually finding the fault, by the way.
     
    • Agree Agree x 1
  4. Fireblade9

    Fireblade9 New Member

    At a guess I think the system is pumped there is a pump near bottom of cylinder

    We did leave the immersion heater on for a few weeks straight just so we didn’t have to keep remembering to put hot water on
     
  5. Fireblade9

    Fireblade9 New Member

    Th
    Thanks

    The level in F E tank never moves I put a mark on the side and water level still there weeks later

    The two tanks are side by side on a platforms the cold shut off level is a fair bit higher than F E water level

    I worry about if it’s over flowing and overflow pipe iced over then the tank would over flow hope that made sense lol
     
  6. Fireblade9

    Fireblade9 New Member

    Thinking heating system is pumped
    HW gravity also should have mentioned we never switch immersion on just use boiler for hot water
     
  7. Jim Goodenough

    Jim Goodenough Member

    Is your hot water hotter than usual?
     
  8. Fireblade9

    Fireblade9 New Member

    No just the same it’s not discoloured either
    Would any pictures be of any help in loft or cylinder layout
     
  9. Fireblade9

    Fireblade9 New Member

    74F08ECF-6258-4EBA-95B5-8999DA08ADFA.jpeg
     
  10. Fireblade9

    Fireblade9 New Member

    B0CBA0B0-8B5E-48E7-91CC-EFE1FC63AE95.jpeg ABC8AB59-DDCC-4A81-8A61-05A95DF8ABD6.jpeg 90B236AD-26D3-4977-835C-8432472964F4.jpeg 827DBE3E-2DC0-44EA-9ADE-7BC530E9BC95.jpeg Few pics
     
  11. Jim Goodenough

    Jim Goodenough Member

    Thanks for the pic, your system is fully pumped - it's great to see the pipes in the cupboard insulated as well!

    BTW did you replace the float "ball" when you replaced the ball cock? What I'm getting to is the float "ball" filling with water and opening the valve?
     
  12. Fireblade9

    Fireblade9 New Member

    I didn’t replace the ball I gave it a good clean and shaked it couldn’t hear any water inside it but there only cheap I’ll get on tomorrow and give that a try
     
  13. Jim Goodenough

    Jim Goodenough Member

    If there was no water in it that won't be the cause of your overflow problem.
     
  14. Fireblade9

    Fireblade9 New Member

    Also when the cold feed pipe is hot and I go in the loft look in cw tank I can see the swirls like it’s filling up from the bottom Iv filmed it but can’t upload clip yet
     
  15. Best

    Best Trusted Plumber

    A mixer (shower or tap) can be passing mains cold water into the hot pipework and it will back fill through copper cylinder and up the cylinder feed pipe and into cold tank.
    Monobloc mixer tap, like on a kitchen or basin are suspect.
    Water passes through them while they are turned off if they have a fault. Even a pin hole of a connection inside the mixer tap between gravity hot & high pressure mains cold will cause an overflow on cwt.
     
    • Agree Agree x 2
    • Informative Informative x 1
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