Boiling water in header tank - URGENT HELP!!!

babyangel10

Hi there,

Earlier today I noticed I had no hot water, (timer set for hot water to come on in the a.m and p.m and never any probs before) so I switched the boiler on boost and all seemed well, then about half an hour ago I heard a weird noise, went upstairs to investigate and the header tank's lid in the loft was almost levitating due to the water in there boiling!

I (after having a major heart attack!) thought that the best thing to do would be to drain the tank, so turned the hot taps on throughout the house and the water, which is normally set very low - about 50 degrees, was absolutely roasting - to the point where I couldn't even touch the hot tap to turn it off cos it burnt my hand! :eek:

Even the water in the cold taps upstairs was coming through warm

I have now drained the header tank and cold water is slowly coming back in, but has anyone got any idea why on earth this has happened? It has frightened me big style cos the tank is in the attic directly above my daughter's bed and it doesn't bear thinking about what might have happened had we been asleep and it overflowed and came through the ceiling.

I have a hot water cylinder in an airing cupboard in case it's related?

I have got a plumber coming tomorrow anyway for something unrelated, but should I get the hell outta here tonight?

I have turned the boiler off so that no water will be heated up overnight - is there anything else I should do?

Please help

ben500

Can't be sure but sounds like your thermostat has gone, what system do you have? If it's gas I'd shut it down until it's inspected, even electric thermo's can burst your tank if you have one.

Canucklehead

Hi

I agree with ben500 cylinder thermostat is keeping the boiler firing and the result is boiling water.
Hopefully the plumber can help you tomorrow .
You should be ok tonight.

Good luck

Corgi Guy.

babyangel10

Thanks for the quick replies so far you two, (I was hoping you were on tonight, Corgi guy!)

Have I done the right thing in keeping the boiler off and draining the header and letting it refill with cold? or shall I just turn all the water off completely at the stopcocks?

Thank goodness my brother lives just across the road so I can go somewhere to shower in the a.m!

babyangel10

I forgot to add that there is a switch in the airing cupboard too, which is connected in some way to the cylinder - I switched it off also - was that ok?

Canucklehead

Hi again: Just turn the boiler off but leave the water on.

Corgi Guy

ben500

gertybertyangel wrote: »

I forgot to add that there is a switch in the airing cupboard too, which is connected in some way to the cylinder - I switched it off also - was that ok?

The switch might mean you have an electric thermo, another indicator is a large electrical connection near the base of the tank although sometimes at the top.
Take a look here for both types

http://www.diydoctor.org.uk/projects/domestic_hot_water_systems.htm

If this is what you have then most likely it is the thermo and not too much trouble to replace but can be costly dependant on your location and the type.

babyangel10

Thanks again for your replies - I have survived the night without being boiled alive so that's a bonus! Cold water coming out of both taps as I thought it would, and the tank is full of cold so that's good. Boiler left off as advised though.

Plumber on the way soon so fingers crosses it's a nice cheap solution! (plumbers=cheap? hmmm - I think not!)

david29dpo

If you heat the water with electric, its the thermostat, about £10 and easy to replace. with gas, also the stat, strapped to the tank, about £15 and also easy to replace.

babyangel10

Well, I thought I'd just give a quick update for anyone who is interested!

Wasn't the thermo after all - the attic has 2 tanks - a large one and a much smaller one - apprently called something like a feed and expansion tank (I think!) and the float valve arm thingy had jammed on, thus meaning no water was coming out of it when necessary and it was empty.

Still not 100% sure of why that meant that the boiling water happened, but not too fussed now it's fixed!

And the cost? Nought pence! Nice Mr Plumber!

Thanks to those on here who gave their input too - apparently if I'd have been out or away that night there was the potential for the whole thing to go bang and flood the house with boiling water! Nice eh - especially as I have just had my new extension finished! I wouldn't have been too chuffed about that happening eh?!

So, for anyone else having boiling water in the big tank - check to see if your little tank (if you have one) contains water too - if not, then that could be your prob.

Canucklehead

Hi


I think that your problem has not been resolved.Sorry!!
The F&E tank being dry will have the opposite effect. The system will slowly lose it's circulation, eventually the pump will not have water to pump and the boiler will only fire for a short time then shut down for hours.You will get no hot water.This takes place over a long period of time as water evaporates.
IMO your system sounds as though the cylinder stat is sticking in the 'on' position and the boiler will fire for as long as the programmer allows it .
Please keep a very close eye (and ear !) on your system.
Perhaps programme your system so that it won't fire overnight? (If it doesn't already)
Corgi Guy.