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

    Do you mean letting by in conjunction with a split coil in the cylinder?
     
  2. Tiago

    Tiago New Member

    Yes! Usually, I set it to heat for 1 hour a day in the evening.

    But since this started I turned the program off, and I've heating it just for a 20-30 minutes a day, enough to have a quick shower before the tank fills too much with the mains open.
     
  3. terrymac

    terrymac Well-Known Member

    Exactly.or a pin hole.
    If the pumps electrically isolated and water level continues to rise ,it can't possibly be the pump.
     
  4. Mike83

    Mike83 Well-Known Member

    F1DF0851-6781-49BD-9CBB-87AF5211A145.jpeg So warm water is definitely going up this pipe.
     
  5. Mike83

    Mike83 Well-Known Member

    There could be a plumbing issue elsewhere judging by that airing cupboard
     
  6. Mike83

    Mike83 Well-Known Member

    It’s possible but unlikely.
    I’m not sure if it has a built in filling loop.
    Most older system boilers didn’t.
     
  7. terrymac

    terrymac Well-Known Member

    Are you sure no other mixers are fed cold water from mains ?
    Turn main stopcock off ,and run all cold outlets ,if cold water still comes out they are tank fed.
    Can you also please take pics of pipework around boiler , would like to see if there is an external filling loop.
     
    Mike83 likes this.
  8. Mike83

    Mike83 Well-Known Member

    Someone could have tried to fit an outside tap with both a hot and cold with isolation valves.
    Maybe the cold is turned on but the hot passing.
    Sometimes diy plumbing throws up allsorts.

    Not seen allsorts in a while on here.
     
  9. terrymac

    terrymac Well-Known Member

    Another possibility. I think I know why previous occupants of the property left !!
     
  10. Mike83

    Mike83 Well-Known Member

    It just seems like there’s a water main connected to the hot somehow.
    Your water level wants to reach higher than tank level.
    It can only be caused by a pump or water main.
     
  11. Tiago

    Tiago New Member

    @terrymac & @Mike83, here's the tap situation, I filmed it in 2 different scenarios - always with pump off, and cold water tank with water.

    Mains Off:



    Mains On:



    ^ weirdly the bathtub tap seems to have water once opened in the cold, but switching to hot and back made the flow a lot lower.

    I tried to take a picture of the boiler pipes, but someone had a great idea of making it very hard to remove the board with some kind of sealant, does this helps at all:


    IMG_2030.JPG IMG_2036.JPG IMG_2037.JPG
     
  12. Tiago

    Tiago New Member

    I left the bathroom tap open for a few minutes (with mains off) and it went dry. But it's definitely fed by the pump because it kicks the pump in when open and I can see the pressure.
     
  13. terrymac

    terrymac Well-Known Member

    Basin tap is a bit suspect ,if its cold position runs dry with mains off ,it would be indicative that its not tank fed ,unless the loft tank was short of water. There was definitely more flow when mains was put on at the basin tap ,but I would have expected it to be even greater, unless there is a valve under the basin that's part closed.
    Can you take pics of pipes under basin ( looking for valves like you took pics of under kitchen sink).
    Boiler pics don't show much ,but I can see a silver braided flexible hose ,which is likely the filling loop, one end is visible. Can you follow that flexi and take pic of the other end of it ,which should have a lever valve.
     
  14. Tiago

    Tiago New Member

    Thanks @terrymac,

    So for the boiler part, I think these are the 2 ends:
    IMG_2041.JPG IMG_2043.JPG

    Then for the sink, it's quite hard to get a closer look. The same sealant between the tiles was applied to the "removable" plate of it.
    This is what I could reach, and with a zoom:

    IMG_2048.JPG

    IMG_2050.JPG

    But this is all protected by this, do you think it will come off if I unscrew it?
    IMG_2051.JPG
     
  15. Tiago

    Tiago New Member

    Also, the insurance is sending a boiler engineer tomorrow, is there anything technical I could tell him to look for?
    I'm going to mention the loop thing, probably see if he would be kind enough to read through this thread haha.
     
  16. terrymac

    terrymac Well-Known Member

    Thanks ,the isolators to basin taps look OK ,full on.
    The braided hose is your filling loop ,if you look closely you will see a black plastic lever at the end.Its that lever that you turn ,only a quarter turn ,to let water into boiler to top up pressure to 1 bar.
    When 1 bar is reached ,make sure you fully close the valve.
    Hopefully your engineer will suss out tomorrow what's going on ,and I doubt he will want to read all this thread ,he can establish on site far more than we can with a few pics.
    Here is what you should tell him as facts established by yoiu....
    1. The loft tanks water level rises to overflowing ,despite the ball valve not letting water in.
    2. You have seen water coming into the tank from the tank outlet( cold feed to hot water cylinder),and this happens when shower pump is electrically isolated ,and boiler is off.
    3. When water mains is closed at stopcock ,water no longer back fills the loft tank.
    4. The boiler pressure gauge is zero.
    Then its down to him ( or her)
     
    Mike83 likes this.
  17. Mike83

    Mike83 Well-Known Member

    Let us know what happens tomorrow.
     
  18. Tiago

    Tiago New Member

    Thanks so much!
    You guys will be the first to know about what happens tomorrow!
    Wish me luck!
     
  19. Tiago

    Tiago New Member

    Ok... So here's what he said.
    He believes some pipe inside the hot water tank is broken, and because of that the pressure is down and the water is going backward.
    He sees 2 solutions:
    A) replace the whole thing with a combi boiler
    B) replace the hot tank, but according to him the pressure changes of doing this will also require changing the boiler because it's old.

    I'm slightly suspicious as he said he could indicate to me someone for the boiler work.
    Having a combi boiler would be a dream, but there was a report years ago that I didn't have enough gas pressure... he said I could replace the gas hob with an electric one to help with that.

    So, nothing is solved, still in despair
     
  20. Mike83

    Mike83 Well-Known Member

    If the pipe inside the water tank was faulty your pressure on the boiler would constantly need topped up unless the filling loop was passing.
    If the filling loop was passing then I would expect the pressure gauge to be reading a bit higher than it’s showing.
     

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