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Discuss Cold water loft tank overflow problem in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. kevtheplod

    kevtheplod New Member

    Evening all,
    Need advice....I have recently purchased a house which needed lots of work doing. It has no mains gas so everything is electric, radiators and immersion for domestic hot water. The main stop cock has been off for about a month whilst refitting the kitchen and bathroom. A week or so again turned it back on and within a day or two I noticed that the cold water loft tank was overflowing. I replaced the entire ball valve unit and observed it working fine, closing the inlet valve when water was about 2 inches below the overflow pipe. Within a day or two noticed the overflow dripping again. Upon checking appears that the ball valve is working fine with no leaks or dripping whatsoever. The only other potential source of water is via the immersion tank expansion pipe which enters the cold water storage tank at the top, although upon checking this it appears dry. The immersion tank has not been changed or altered in any way, nor has the cold water tank (with the exception of the ball valve unit). The immersion heater element thermostat is set at 60 degrees and the water hot temperature when checked is coming out of the tap at about 56 degrees. Any idea what could be causing the problem?
  2. Craig Watson

    Craig Watson Plumber GSR

    You could be getting mains water passing through a mixer tap/shower. This will backfill through your cylinder and into the tank.
  3. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Sounds likely
  4. kevtheplod

    kevtheplod New Member

    Hi Craig & Riley,

    Thanks for your replies. I've got to be honest I didn't think that was even possible...that said I am absolutely no expert. I'll be getting a plumber in to check the system out asap! Out of interest are you suggesting that it is back filling via the cold water tank outlet pipe or via the expansion pipe?
  5. Craig Watson

    Craig Watson Plumber GSR

    It can back fill through the outlet.
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