Cold water tank overflowing with hot water

Discussion in 'Plumbers' Talk' started by Tiago, Oct 8, 2019.

  1. terrymac

    terrymac Screwfix Select

    The saga continues !
    I assume your insurers will not accept liability for the hot water cylinder replacement ,if indeed that's what's required ,as that would be wear and tear. So you would likely be looking at quite a bit of outlay ,even more so if you are thinking of having a new boiler as well. Why are you getting quotes for a new boiler ??
     
  2. Tiago

    Tiago Member

    Yeah, my initial boiler idea was to go with a combi, and get rid of all this madness.
    Replacing my current boiler is my last resource! I'm hoping that even if I have to pay, replacing the hot cylinder will bring me peace again for a while.
     
  3. Mike83

    Mike83 Screwfix Select

    Don’t let anyone change the cylinder without confirming if it’s the coil first.
    Even upgrading the boiler and keeping it a system may involve the gas pipe needing upgraded.
     
    terrymac likes this.
  4. Tiago

    Tiago Member

    British Gas engineer is here, he could not top the pressure to 1 bar, it stayed a bit above 0.75. But it’s holding so far
     
  5. Tiago

    Tiago Member

    Ok just more updates from today’s engineer.

    he doesn’t think there’s anything wrong with the boiler or the tank.
    He drained the pressure of the boiler, opened mains, the pressure didn’t move.
    Than he refilled the pressure (it only went to 0.75ish, and closed the loop, but the pressure remained.

    we removed all water from the tanks to see if it would affect the pressure, but it didn’t.
    I’ve now opened the mains again and I’m filling the tanks a little bit
     

    Attached Files:

  6. Tiago

    Tiago Member

    So if it’s not the tank and the coil, is there any other theory of what it could be?
     
  7. Tiago

    Tiago Member

    An updated picture of the boiler pipes, we managed to remove the panel.
     

    Attached Files:

  8. Tiago

    Tiago Member

    @Mike83 & @terrymac I literally ripped of the tiles in the bathtub to try to isolate that mixer, but the problem still happens.
    The only mixer I didn't isolate is the basin tap, which I can't reach... is that the last option?
     
  9. terrymac

    terrymac Screwfix Select

    What was the engineers diagnosis ? What reason did he attribute to the loft tanks rising water level ?
     
  10. Tiago

    Tiago Member

    He didn’t attribute it to anything. He was the gas engineer, the only think he said is that it is not the tank, because the boiler kept the pressure and the problem persisted.

    I’m literally desperate now
     
  11. Tiago

    Tiago Member

    When you guys said to isolate the filling loop, is it just turn the black thing off? Or is it also about twisting the screw at the other side of the flexible tube?
     
  12. terrymac

    terrymac Screwfix Select

    Can you look at the 4 flexible hoses that connect the pump to your pipework. Your pic shows what looks like a black isolation valve on the end of each flexi. Probably just a slot where you can put a screwdriver ,within the black section. ( a bit like the valves that you isolated the kitchen tap). If this is so ,please close the valve on the flexi that is connected to the pipe that leads to the top of your hot water cylinder ( so its the hot feed to the pump).
    Leave electrics to pump OFF.
    Put boiler on ,both central heating
    and hot water.
    Leave mains water stopcock on.
    Tell us if the loft tank water level still rises to overflow.
     
  13. Tiago

    Tiago Member

    I’m going to observe it more, BUT it seems to stop in the conditions you mentioned.
    Weirdly there are still hot water coming from the hot taps though, which I thought would be impossible with that closed.

    I’m going to observe the tank more, because if it’s feeling with cold water now instead of hot I won’t be able to see the flow in the bottom, just the level raising.


    Suppose it’s not overflowing anymore, what could this mean?
     
  14. Tiago

    Tiago Member

    @terrymac so the boiler finished an 1h cycle, the mains are still open and the tank seems to have stopped before the overflow mark.
    I’m still monitoring it, but previously it would be well above the overflow line at this point. So I think you might be on to something
     
  15. terrymac

    terrymac Screwfix Select

    Early days yet ,see what develops.
    You will still get hot water ,as it will flow down the expansion pipe through the T ,into the distribution pipework.
    I am hoping the non return valve is actually doing its job ,if it is ,water level in loft tank will not rise unless the cylinder coil is kaput.
     
  16. Tiago

    Tiago Member

    if the cylinder coil is fine and the tank doesn’t overflow, what does it leave as the possible causes?
    They guy today also mentioned that if the coil was broken I would be seeing some very nasty water out the taps - quite scary.
     
  17. terrymac

    terrymac Screwfix Select

    A question. When loft tanks ball valve closes ,how much lower is the water level ( so its " normal" level ) below the overflow spill over level ?
     
  18. Tiago

    Tiago Member

    I’m monitoring it with pictures, so I’ve many to show haha
    This is about when it stop filling through the ball cock valve:
    Apologies , the picture went upside down
    Let me fix
     

    Attached Files:

  19. Tiago

    Tiago Member

  20. terrymac

    terrymac Screwfix Select

    Can't tell ,but looks like ,5 inches or more from the bottom of the white overflow pipe ,is it ?
     

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