Cold water tank full of hot water.

[jackplumb]

Just visited a house with a tank full of hot water and it is overflowing. The immersion and thermostat have been replaced and still the problem was there, the immersion has been off for several months so a faulty termostat can be ruled out.
There are four pumps in the house for showers etc could one of the seals have gone causing the cold to mix with the hot.
It's hard to see whether the cold is mains or gravity fed, but surely if it was gravity pressures would be equal and wouldn't cause overflow. Would it be best to isolate each one in turn to find the culprit?

 

[jackplumb]

Sorry should have said it's the CWSC in the loft that is hot.

 

[PlumbBobBob]

are there any monoblock taps kitchen or bathroom. have they just recently had a new washing macnine?

 

[Simon F]

if the ch is open vent, what height is the f+e in relation to the cwsc

 

[jackplumb]

Yes I think so, worth checking as well, hopefully they can be isolated individually. They have also had problems with one of the showers not working properly and only suppling hot water, not sure if the problems are related though.

 

[Puddle]

You are going to have to find what is mains and what's tank fed

Simple test.turn mains stop valve off and see in cold outlets stop running,if so mains,if not tank fed,if any mains on showers,this could be the problem

imho

 

[Resolute]

What's the HWC like? Could the coil have pinholed in the cylinder?

 

[Puddle]

What's the HWC like? Could the coil have pinholed in the cylinder?

certainly could,maybe that is what Simon was thinking

 

[Simon F]

:iagree: if the f+e is higher than the cold tank and the coil gone, the symptoms
would be as described

 

[glenno1]

is cylinder stat working

 

[SPH]

hi either you have mains water going back up the hot or if the f&e tank is higher than the main storage tank a pin hole in the hot water cylinder coil
check by not having any water running and look inside cold water tank at the outlets you will normally see a small amount of water flowing back into the tank if you do turn off the mains and see if it stops if it does then poss shower faulty / taps etc.
to check if it is f&e tank bung outlet and vent to see if it stops in the cold water tank

 

[LeakFinder's]

turn off the mains for the f&e and domestic tank run off a bit of domestic hot and see if the level drops in the F&e tank if it does its likely a perforated coil.

 

[arran197]

I had this problem recently, I was arguing with the plumbers (different company and very complicated, but cylinders and f & e tanks are them, not us). He was saying that the boiler was causing the water to boiler in the system and making it overflow. It blatantly wasn't, the ball vale had been changed, but hadn't stopped the problem. It was only happening in the middle of the night. There was a thermostatic mixing valve on the basin, I reckon that was the problem. Not been back to it or heard how it went though.

 

[xpertbert]

If the cold water tank is hot and overflowing, check the heating tank, if the ball valve is filling it has to be coil.

 

[WHPES]

1, Turn off the mains water. If it stops then you have a stuck check valve in a mixer tap

2, Turn off the mains water and leave overnight without drawing off any hot. If both cisterns are level with each other in the morning you have a failed cylinder coil.

 

[jackplumb]

F&E tank is lower than CWSC, not sure about the cylinder stat, although it was set high at 70. The boiler was not on at the time of my visit so it was only previosly heated water that was being push up.

 

[mutley racers]

so jackplumb, what was the out come for this hot cwsc?

 

[Guest123]

Could be the hot supply mixing with the cold feed in a faulty mixer shower. This would force the hot water back up the tank fed cold feed and into the tank causing it to overflow. Non return valves will solve the problem.

 

[MattWeth]

I've seen single ended, monoblock shower pumps have the seal between the chambers fail and allow the cold to pressurise the hot side. Even worse if a shower pump has been connected to mains cold (against regs but people sometimes do it mistakenly).