Hot water in cold tank

[rona61]

Hi, I wonder if anyone can offer any suggestions here, as I am now officially at the end of my tether...

I have an open vent heating and hot water system. Boiler is a Potterton Profile 60 (that's what it says on the front) and is about 4 years old.
4 radiators in a one- bed flat.
No electric shower.
Mixer tap in kitchen - mains fed cold water
Mixer in bath - from storage tank.
Ist floor flat - cold tank in loft, expansion tank is higher than cold tank.

Last weds, the cold tank overflowed. As the overflow pipe was rubbish, it spilled thorugh into the flat.
I had the overflow pipe replaced, so at least now all the water is going outside.
Heating engineers have done various things, including replacing all ball c0cks and valves and raising the level of the pipe that overhangs into the tank - nothing worked. The overflows were even happening a few hours after the hot water and heating were switched off.
Yesterday they decided that the cylinder must be split. They put in a new hot-water tank.
The cold tank has just overflowed again - the heating and hot water had been on for about 2 hours.
I went into the loft and could feel the warm water coming in from the BOTTOM of the tank at a fair lick. I have switched off the system, drained all the hot water, called the engineers again.
Does anyone have any clue what it could be, as they clearly don't? They are a corgi registered company, they installed the boiler and have been servicing annually ever since. Should I give up on them and call in another plumber?

 

[buck51]

I think they should be checking the check valves on the mixer taps, it could
be that one is passing.

 

[seco services]

have you tried shutting your mains stopcock and see if it stops filling the tank.


They are a corgi registered company, they installed the boiler and have been servicing annually ever since. Should I give up on them and call in another plumber?


i would as they seem to be costing you a fortune.

 

[rona61]

It's definitely not mains cold water that's coming in through the ball cock. It was shut tight when I could feel the warm water coming in form the hole near the bottom of the tank - pipe appears to go down to where the hot tank is. And I was getting warm water through the cold tap day before yesterday.

Mixer tap: They told me it could not be this - something to do with the fact that the bathroom mixer was not mains water? Didn't really understand this, should I insist on this?

Could it somehow be the thermostat on the hot tank? They didn't replace this on the new tank, again said it couldn;t be that, as boiler thermostat would be controlling it.

Many apologies that I don't really know what I am talking about here - just relaying what they have told me.

EDIT: they haven't cost me a fortune yet, as pretty much everything they have done has been part of the gold insurance I've got... but I can't go on like this, it's been 10 days and no solution!

 

[seco services]

i never said through the ballcock.

i said shut mains stopcock and it will stop.

its a mixer tap thats passing cold to hot. if the bathroom one is fed hot/cold fom the tank its the kitchen mixer then.

as that will be gravity hot mains cold.

10 days more like 10 min job.

 

[rona61]

Apologies, seco, for not understanding you.
I can get it to stop by shutting down the boiler, switching off the power, and running the hot water out of the tank through the taps. What I don't know how to do is stop it happening in the first place!

Many thanks for your reply re: kitchen mixer. Can you explain what 'passing' means in this context?

 

[seco services]

Apologies, seco, for not understanding you.
I can get it to stop by shutting down the boiler, switching off the power, and running the hot water out of the tank through the taps. What I don't know how to do is stop it happening in the first place!

i just told you.

shut the mains stopcock.
then feel the pipe in the bottom of the tank. i bet it has stopped it filling.

let me know if it has or not.

 

[rona61]

It has already stopped, so I can't check by turning off stopcock now. So sorry, I realise I am being an irritating know-nothing poster,the kind it is very hard to help.
If it starts again, I will turn the stopcock off (the one by the tank, or the one in the street?)

 

[seco services]

how has it suddenly stopped ?

 

[rona61]

It stopped after I shut off the boiler, turned off the electricity to the hot tank and boiler and ran all the hot water out of the taps.

 

[seco services]

yes
but surely the pipe in the bottom of the tank as you said was filling with warm water still is.
it won't overflow cause you have drained the tank down but it will still fill.


whats the electricity to the cylinder for ?
your not got the immersion heater on have you ?

 

[rona61]

I've just been back up. Put my hand over the pipe inlet, couldn't feel any flow of water at all.
It has been an intermittent thing the last 10 days, overflowing twice in a few hours, then not for over 24 hours. The only thing that seems to stop it completely is when I do what I said - get rid of the hot water in the tank and turn everything off (leaving the mains water on though.

The electricity is for the clock and the thermostat I think. The immersion is definitely not wired up - they removed it when they put this new boiler in.

 

[seco services]

ok

do you find it does it after you have used a certain appliance ?

 

[matt1e]

when they replaced the ball cock in the cold storage tank did they set the water level correctly? there has to be room to allow for expansion

 

[rona61]

No, not really. Tonight I hadn't used anything - the heating/hot water came on on a timer at 5pm, I didn't run any hot taps in that time (maybe filled the kettle/flushed the loo), and I heard the overflow start gushing outside at about 7pm.

The night before last, I had the system on until about 8pm, then it switched off, and I had overflows at midnight and again at 4am. At 4am, the water was still very hot coming out of the taps, hotter than I would have expected. I ran all hot water out of the hot tank, switched off the electricity, just in case that somehow affected the thermostat or something and it didn't overflow again between then and when engineers turned up at about 11am.

Edit: Mattie, not sure what correct level would be. Looks to be room to me, but wouldn't it flow outside from the expansion tank overflow pipe if there wasn't enough room in that tank? Not had that (yet!)
Will ask them to recheck that anyhow.
Oh just read again, you said cold tank not expansion tank. Surely cold tank doesn't need exapnsion room??