Cold Water Tank Help

Discussion in 'Plumbers' Talk' started by skybluekev, Oct 14, 2019.

  1. skybluekev

    skybluekev New Member

    Hi, please help.

    I have a vented tank hot water system and standard boiler. In the loft I have an expansion header tank for the heating and a large cold water tank for the hot water. Currently when the heating is on, after a while the cold water tank starts to fill (not the heating header tank) and seems to run slowly but constantly until the heating turns off either through the timer or thermostat. This usually starts to happens when the heating has been on for about half an hour and only happens when the heating is on (except when hot water is being used by the shower or taps etc.). Logic would suggest water is leaking from the hot water system, but no sign in the house, and why only when the heating is on? We have just had some new radiators fitted, and we didn’t have the issue when just the hot water was on before turned the heating on too.

    Any help appreciated.
     
  2. kiaora

    kiaora Guest

    Hi
    If the cold water storage tank starts to fill ?
    Do you mean the water level rises without the ball valve operating?

    if so, it’s probably the coil in the cylinder with a pin hole

    good luck
    Peter
     
  3. skybluekev

    skybluekev New Member

    thanks, no it is filling through the ballcock valve because the level is dropping.
     
  4. kiaora

    kiaora Guest

    Ok
    I’m not understanding the question,
    It’s an age thing !
     
  5. terrymac

    terrymac Screwfix Select

    If the water level is dropping ,then water is leaking out the distribution pipework or outlets. How many pipes exit the loft tank at low level ? It may also feed some cold water outlets ,bath / basin tap/ shower/ wc.
     
  6. skybluekev

    skybluekev New Member

    Just for clarity. Heating comes one, about 30 minutes later the water level in the cold water tank in the loft falls to a point where it starts filling from the ball cock valve. It appears to remain slow but continuous until the heating turns off from the timer or thermostat. There is no overflow, and no obvious leaks (I know the water must be going somewhere). The heating seems fine. As far as I can tell and am aware, the cold water tank feeds the hot water cylinder in the airing cupboard only. The level of the header tank for the heating seems unaffected.

    It's a real head scratcher unless anyone knows why it might be happening.
     
  7. terrymac

    terrymac Screwfix Select

    Your domestic hot water and the central heating water are independent of each other and are not connected .The only place where they can " mix" ,is within the hot water cylinder ,if the coil inside the cylinder is perforated.
    Does your programmer allow you to choose heating of the domestic hot water only ?
     
  8. skybluekev

    skybluekev New Member

    Yes, it doesn't seem to happen when just the hot water is on.
     
  9. terrymac

    terrymac Screwfix Select

    OK ,that's weird. If the central heating is on for say 5 or 6 hours, does the loft tanks ball cock continue to allow water into the tank for the entire period ( obviously you wouldn't be able to use any taps etc ). And please take a look at the loft tank to confirm that there is only one outlet from it.
     
  10. skybluekev

    skybluekev New Member

    It continues to flow as far as I can tell when the central heating is pumping, if the pump stops (i.e. the thermostat turns it off) it seems to stop, but then starts again once the pump kicks back in.
     
  11. terrymac

    terrymac Screwfix Select

    If water is continually going into the tank ,then it has to be going out somewhere. Please confirm the amount of outlets from the tank.
     

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