Hot water is coming out of the overflow pipe..Help !!!!

Discussion in 'Plumbing and Central Heating' started by tometoyou, 8 Apr 2008.

  1. tometoyou

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    After a couple of hours of the central heating coming on we sometimes get hot water pouring out of of one of the overflow pipes in the back garden.

    We have two tanks in the loft which both have connected overflow pipes. One is for water and I asumme the other one is related to the central heating.

    The smaller tank (related to the central heating) is the one which suffers from this problem.

    The tank is supplied by cold water which is attached to a ballcock and another chopper pipe which hangs over the tank. The water level is fine as the ballcock level is around 5cm below the overflow tank. What is strange is that the water in the tank is hot. I can only assume that the overflow is being 'tripped' by the pipe which over hangs the tank.

    I'm not 100% sure what the pipe is but I believe it must be connected to the central heating. Could it be that the boiler is producing too much hot water and is using the tank to get rid of the excess hot water ?

    This would explain why the water in the tank is hot and why the overflow is being tripped even the the ballcock level looks ok ?

    How do we prevent this from happening over then not running the heating ?

    We have tied turning the temperature down using the gauge but the problem persists.

    Any pointers ?

    Cheers !
     
  2. Bahco

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    Drain off water and set the float to cut off water at 4 inches from the bottom.

    Do this with the system cold. :D
     
  3. Watchmaker

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    A DIY reply here so, the experts might well pinpoint the problem more accurately.
    "I'm not 100% sure what the pipe is"
    This a vent pipe. In the central heating system, the central heating water (as well as indirectly heating the domestic hot water tank) is being circulated by a pump somewhere in the circuit. This circuit, connected to the boiler must, in most cases, not be sealed, and any excess pressurized water, or air, must be able to find it's way out of the system.

    It is likely that the "head" of the pump is set too high and most pumps have a device to adjust this "head". If you inspect the pump, you might find a graduated scale and adjuster and, as an experiment, you might try to lower the pump head/pressure slightly. The pump does not shift a lot of water, it only circulates it and assists the natural thermo syphon (hot water rises, cold water falls) effect but, in your case the heating water is being pushed over the vent and into the small make up tank.

    As this hot water will stay at the top of this usually cold tank, the water which you see coming from the overflow is likely to be hot. The system should be checked to see if there are any obstructions etc and a drain down and re-fill, should assist the removal of any debris or foreign matter which could be restricting the water flow.

    If you are not familiar with the system, I suggest that an expert examines the layout and, if all is well, raising the height of the vent pipe, above the tank, might help but, only after any other causes have been eliminated.
     
  4. tometoyou

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    Thanks for the tips.

    I will certainly take a look at the pump tonight to see if I can adjust it.
     

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