Tank Overflow

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20 Oct 2014
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Tyne and Wear
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United Kingdom
I'm afraid I cannot describe the system that well however I have a Baxi Bermuda LWH0345 gas back bolier.

There are 2 tanks side by side in the loft. The whole system is 20/30 years old.

The smaller (header tank?) has had the ball cock and valve replaced and it fills approx to 2 inches only but still overflows when the hot water is switched on. This has worked OK in the past and no recent work done on the system.

Any Thoughts/help would be appreciated Photographs uploaded

 
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The smaller F&E tank takes up any of the additionally expanded water from your central heating system. Upon replacing the filling (ballcock) valve you may find that the warning overlow pipe may spillover a little initially, but should settle down. However!...
If the coil in your immersion cylinder has gone.... then.... you will need a replacement cylider. The coil is inside the hot water (immersion) cylinder. (You may have an electric immersion element fitted to be used in the event that your boiler breaks down... as a back up) The coil inside the cylinder is on the heating radiator circuit. It does NOT mix with the water inside the cylinder itself. It just circulates thru, whenever demand via your timer/controller is set to heat up the water inside the cylinder that is then drawn off thru your hot water taps.
You really need experienced plumber/heating engineer to positively diagnose the fault.
Outside of the boiler cabinet/housing itself, there may be any number of other faults or failures of components that may be affecting the system.
 
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Thanks for the help and suggestions.

Forgive my ignorance but I would normally think of a hot water cylinder as a big copper cylinder. My hot water is stored in the tank in the loft. Is the coil you refer to in bottom of there or in the boiler behind the fire?

Again apologies for my lack of knowledge/terminology.
 
You appear to have an ancestor of this http://www.gotogasdocs.co.uk/download/?i=Elson_Rectangular Combination Tanks_Amethyst.pdf .

They don't make them anymore, and what is meant by a pinholed coil is that water from the central heating system is making it's way into the hot water. Are you sure you don't have another tank, the F&E tank, whose water is higher than the hot water tank and thus creating the overflow? Even if it isn't it might just being pumped in via the pinhole.

you say it overflows "when the hot water is on". We all assume you mean when the water is heating rather than a tap being on. Check back if we're wrong though.
 
Thanks,

I definitely do not have another tank. Its a poor system with only one temp control for both heating and water. Water has to be on with CH.

I could see the F&E tank water rise slowly despite the cold water inlet being stopped by the ballcock. You are correct, It only overflows when its heating water or at least gets worse, Is it likely the issue is within these tanks rather than anything in the actual boiler. I ask because the boiler is covered by British Gas but doubt that would include the tanks??
 
The water filling the water tank through the coil has to come from somewhere. It won't be a big tank possible but there will be something keeping the central heating circuit, including the coil, full of water!

It's not a boiler issue, it's the coil in the tank, the big red thing in the PDF. I don't know whether you can get spare coils but it's worth asking the makers; otherwise you'll need a new tank.
 
It only happen with hot water / heating on, yes?

Possible when pump is on, if on return pipe, created negative pressure, sucking water from hot water side via pinhole coil to heating side?

Can't think anymore.

What boiler, pump and any motorised valve have you got?

Daniel.
 
Thanks again everyone for your time with this.

To clarify I have no other tanks other than the 2 in the photographs I have uploaded. Its a Baxi Bermuda back bolier with HW and CH. Pump under floorboards for CH.

The biggest tank with hot water does not have a coil as in the PDF but what looks like a exhaust silencer in the bottom. I suspect this is the coil then and maybe has a pinhole leak. It overflows when no pump is running.

So it sounds like I have a dodgy coil that needs replaced or even a new tank. I am still confused how the CH system works as defo no other tank!
 
To be honest on a cistern that old and confusing it might be worth just calling up the makers and asking to speak to the Tech Support. They usually hold the oldest technicians there until retirement!

Describe everything that's on the plate.
 
Looking again at the photos it appears the round drum in the middle could be the F&E tank as the water looks more a murky brown, but how it keeps itself topped up is a mystery. How does the level in this drum relate to the level in the tanks?

If the level in the drum doesn't go down and isn't related to the big tank and ball cock tank level then it might be a manual fill type in which case the water height rise will be coming from somewhere other than the coil.

Have you had any work to the plumbing done recently? Perhaps a new or replacement mixer tap? It wouldn't be unknown for water to get pushed back into the tank from the cold mains by either pressure differential on the mixer spout or a fault with the tap itself.
 
Probably not the tap then. Also I just realised if the F&E 'drum' tank does go down when it pumps water into the hot tank, it will bleed back through the hole in the coil and equalise the levels afterwards.

If the filler tank goes up and the drum level comes down during HW heating that will confirm it.

I find it strange though to see an F&E (if indeed that's what the drum is) plonked in the middle of a hot water storage tank. Time to call the maker.
 

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