Boiling water in header tank - URGENT HELP!!!

absfabs

I'm not a plumber or any kind of expert.

But IMHO the thermostat should shut things down if the water gets to certain temperature, never mind if there is problem with water inlet. If it doesn't shut it down, it's not working and not safe.

Above poster is not happy with your outcome either and sounds like he knows what he is talking about.

I would get someone else in to look at it/?replace thermostat.

CLAPTON

The details are not quite clear

a. which of the two tanks has a sticky ballcock... the little header tank or the larger tank

b. do you have an electric (immersion ) heater for the cylinder as well as heating based on the boiler.

If so i would suspect that the electric immersion heater has a fulty thermostat and the problem appears to be fixed because its now turned off and the heating is coming from the boiler.

sooz

I read your post and remembered seeing this article.

'HSE safety alert of scalding risk from domestic hot water systems' - it's near the bottom of the page http://www.landlords.org.uk/news.asp

babyangel10

Thanks for the further info guys - I'll certainly take it seriously and get a second opinion asap - all seems well at the mo and I only put the boiler hot water boost switch on when I'm in, just in case.

That looks interesting reading sooz, I'll have a proper read of that later.

And Clapton, it was the small tank that the ball valve arm had jammed on - the tank was empty and the ball valve or some sort of fitting around it anyway (if I'm right - the springy thing that allows the water to come out when the ball is pressed down slightly?) was just a bit limed up and the plumber cleaned it and ever since it has filled up all has been ok.

And yes, I do have an electric immersion heater as well as the boiler and that switch is still turned off, so you could well be right about the thermostat being faulty in there.

Is that a possibility Canucklehead/Corgi Guy? (not that I'm doubting anyone - just want a second opinion!

Thanks again for the inputs :beer:

CLAPTON

You could try turning the immersion heater on (say) at the weekend when you can watch it and see whether it over heats...
if it is the problem and you are electrically minded then its usually an easy and cheap job to fit a new thermostat... i would also suggest you fit a timer switch at the same time so it only comes on for an hour or so just in case it happens again.

BobProperty

IMHO there are a number of possibilities to cause this problem. In the mean time do not heat up the water. That means no HW from the boiler and no immersion heater(s), timed, Economy 7 overnight or anything.

Possible causes are thermostats not working, as has been suggested, and that would include the upper limit stat on the boiler as well as the stat on the HW tank. (Depends on your set up). Canucklehead, (or anyone else, but I know Mr Canucklehead is a CORGI plumber), I think you can get this situation if the heating coil in the tank has split, too.

Please, anyone reading this, do take this problem seriously.

babyangel10

Thanks bobproperty and Clapton - I am definitely taking this very seriously, especially after reading the link on sooz post about the 2 poor people who dies from the ceiling giving way and boiling water landing on them

That potentially could have been my daughter as the tank is above her room

The house is only about 9 years old, so it is a worry that something like this could happen in a relatively new house.

I am definitely gonna sort out one of the immersion tank thermo's with a overheat safety cutout too, as read about on another site - mine evidently hasn't got this on it.

Luckily, as well as my brother living just across the road, my neighbour is away for a few days so I can use his shower if necessary too, and chuck him a couple of bob for the privilege.

I just am so glad I was home when this all happened...

ben500

I wouldn't relax just yet, It still strikes me as being your thermo not cutting out I would definately seek a second opinion if I was you, you can of course as others have suggested try switching the immersion back on when your in the house for a lengthy period to see if it overheats again but make sure you don't get distracted and forget about it better to set an alarm clock to remind you to check it.

There was also a case earlier this year where an overheating immersion tank exploded and doused a sleeping child {a young girl if I remember rightly} in boiling water, she died!

Bear in mind also that immersion tanks tend to be fitted to smaller bedrooms in the property which are generally occupied by the children rather than the parents. This is not something to take lightly as an above poster has pointed out. Also whilst this water is boiling it will also be condensing somewhere in the property and this may cause mould growth in that area so have a good look around the loft space and try to clean off any residual moisture once you have resolved the overheating problem.

jamesrice

The fact that your feed and expansion tank ball valve was stuck is definatley not the problem, the feed and expansion tank is only to allow expansion for hot water in the central heating circuit and cylinder coil, if anything the boiler should of cut out due to low pressure. Is the cylinder stat (usually a rectangle block with a dial on it about a third of the way up the cylinder) set to 65 - 70 degrees? there is no possibility of you accidentaly or a little kid turning any of the gate valves (taps) on any pipework causing it to pump over? dont use the hot water at all unitl you can be sure of whats caused it as the plumber has not fixed it. Hope this helps.

Canucklehead

Hi

The original post did not suggest that the immersion heater was in use only the boiler, however it's not uncommon for the immersion to be left on as well as the boiler.
gertybertyangel... if you or your brother are confident then check the immersion stat. Start by taking off the cover (with power off) you should now see the top of the stat with two wires on it. There is a temperature scale and usually a screwdriver slot in the middle of it with an arrow.If you have hot water in the cylinder then turning the stat with a small screwdriver will produce a small 'tick' from it.turn it both ways fully and it will 'tick' twice
on/off. If you don't have much hot water it might not work but that's the theory.(leave stat @60 degrees when finished)
If you need a new stat you should only be able to buy one with an overheat cutout and manual reset button.

The cylinder stat is the item that needs testing/replacing it's the only thing that governs the temperature of the water in the cylinder.
As far as I know the only thing that happens when a cylinder coil splits/pinholes is that one of the tanks in the roof overflows (starting as a drip and getting worse slowly) and maybe discoloured water from the taps, it depends which tank is lower.

That being said this is 'blind ' diagnosis!!!!

HTH.
Corgi Guy