Cold water tank overflowing with hot water

Discussion in 'Plumbers' Talk' started by Tiago, Oct 8, 2019 at 5:31 PM.

  1. Mike83

    Mike83 Well-Known Member

    At least the new plumber knows his stuff and it coming out with solutions.
    But turning the pump off should stop the fault occurring.
     
  2. Tiago

    Tiago New Member

    Yeah, those two red lines are the same pipe, the guy today was very shocked with that, that apart from feeding the house (going down and left), it was also going up (through the non-return valve and connected to the tank again).

    Also, once he closed the valve that feeds water from the cold tank to the hot tank (the pipe from which the water is entering the cold water tank instead of only exiting from it, the main problem), the water started to enter the cold water tank through the top (the pipe that according to him only should carry steam from the hot tank, and it's also connected to the pump through the non-return valve).

    @Mike83 sadly it happens even with the pump off (from power).
     
  3. Mike83

    Mike83 Well-Known Member

    The pump could pump water upwards and back into the tank with that plumbing setup with the faulty nrv.
    But with the pump turned off this couldn’t happen.

    What make and model of boiler do you have?
    Is it a pressurised system?
     
  4. terrymac

    terrymac Well-Known Member

    If the water level in the loft tank is rising ,and the pump is not switched on ,then the water has to be coming from the mains or a tank at a higher level.
    With pump off ,turn off your mains stopcock ,and see if the water level in loft tank stops rising.
    The plumbings a rats nest ,and there should not be any non return valve on the expansion pipe. Have it removed.
     
  5. Tiago

    Tiago New Member

    It's a Vaillant, but I think the model is "thermo compact" but I don't know about pressurised or not,
    here's a picture of it:
    IMG_2029.JPG
     
  6. Tiago

    Tiago New Member

    The water only raises if the mains are open - independent of the pump being on/off.

    Does it make any sense for the pump to also be connected to the expansion pipe?
    Because the guy wants to remove that connection, as a person with zero experience as I am, I'm scared.
     
  7. terrymac

    terrymac Well-Known Member

    The boiler pressure is Zero ,how often are you topping it up ? That's a possible source of mains water into hot water system via the cylinder coil.
     
  8. Tiago

    Tiago New Member

    omg, it has been pretty low since I moved in, I thought that was only for the house heating :(
    Is there anything I can safely try to do to increase it and double-check?
     
  9. Mike83

    Mike83 Well-Known Member

    Have you been having to top the pressure up on your boiler recently?
    Just noticed terry asked the same.
     
  10. Tiago

    Tiago New Member

    Not really, I have no idea how to do it. I've moved to this place about 7 months ago, I had house heating on for a couple of months and didn't have it on yet (for that)
    I was going to get it serviced after this water situation was solved
     
  11. Mike83

    Mike83 Well-Known Member

    It’s needs topped up but it’s not important to this issue.
    If the pressure was regularly getting topped up it could have explained the issue.
     
  12. Mike83

    Mike83 Well-Known Member

    49369E1E-276F-40AB-AC66-E516C4DBB562.jpeg
    None of this section in needed.
     
  13. Tiago

    Tiago New Member

    This is good to know! Because that's exactly what the guy from today wants to remove.
    Do you think this alone would solve the problem?
     
  14. Mike83

    Mike83 Well-Known Member

    If turning the pump off fixed the issue then probably.
    There’s something else happening with this.
     
  15. Tiago

    Tiago New Member

    Damn :(
    pump off (from power) doesn't fix the issue...
    The water can still go through it when it's off, but I guess that doesn't matter right
     
  16. terrymac

    terrymac Well-Known Member

    Just realised the non return valve is a lot lower than I originally thought, so not as much of an issue .
    Do you use the boiler to heat your domestic hot water cylinder ,or the electric immersion heater ?
     
  17. Tiago

    Tiago New Member

    I'm not super sure, but I always thought that it heated the hot water cylinder, it's a gas boiler
     
  18. terrymac

    terrymac Well-Known Member

    Mike ,any experience of this boiler ,wondering if filling loop is internal and letting by ,maybe ??
    If there are no other mixer taps /shower valves in the property and given the following facts
    1. Mains off ,no water level rise at cwsc.
    2. When pump is off ,level rises ( obviously rules pump out)
    3. Kitchen mixer isolated ,but mains on ,level rises.
    4. Hot and cold from same head.
    I cant think it can be anything other than the filling loop.
     
  19. terrymac

    terrymac Well-Known Member

    Yes it will ,but you must control it/ create the demand,either with a timer or programmer,etc.
     
  20. Mike83

    Mike83 Well-Known Member

    Once that pump starts, coupled with a faulty nrv it may continue to run as the water is pumping around a circuit.
     

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