Combi Boiler

discobobby | 18:58 Thu 13th Feb 2014 | DIY

21 Answers

I have a Worcester combi boiler, every other day the gauge keeps going down, I cant find any leaks, why does this happen.
Any good heating guys out there who can help?

many thanks
Bob

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gness

When mine did that it was a small leak in the pipes under the floor. Is that a possibility?

The Builder

If you're certain there are no leaks (it takes very little leakage for the gauge to drop), then possibly, your expansion vessel needs re-charging.

They usually have a Schroder valve on top of them (standard tyre valve). They're re-charged with a footpump.

If you can locate the discharge pipe on the outside of the house (usually 15mm copper tube), stick a jamjar over it and check it the next day. If there's water in it, it could be an indication that the system is blowing water out because the expansion vessel s deflated, thus unable to "cushion" the excess pressure.

discobobby

Question Author

Cant find any sign of a leak.

gness

While you are around, MrBuilder.....my problem was solved by getting the installers to add something like Radweld. They weren't too happy and wanted to quote for digging up the floors or re-piping.
Is the Radweld likely to last? It's been over two years with no problem...Gx

gness

Bob....how long have you had the boiler?

tonyav

Radweld, gness, that's what you use for leaky car radiators. Didn't know there is a version of it for central heats rads.

gness

No-one told me when they were quoting for expensive work, Tony....mine was a new boiler in a thirty year old house and they said I would have to have the pipes re-done to match the boiler.
I made a throw away remark about Radweld and discovered it could be done on my leaks.....worked a treat and saved a lot.

The Builder

Yes Tone, there is a "Stop Leak" or something similar for rad systems.

Gness, I honestly can't see why Radweld shouldn't work, unless the manufacturers say that it might be detrimental to the gubbins ;o)

tonyav

Useful tip that, gness, I suppose that if it's works in a car rad then there's no reason why it won't work in a central heating system.

gness

Thanks, Mr Builder....I was told you can't do it more than twice but it's been fine so far and the money saved and spent on wine and shoes made me very happy....☺

sherrardk

When it happens with mine I bleed the radiators and then top the boiler back up.

BRIGHT SPARK

If you put Radweld or similar into a modern boiler then say goodbye to any warranty.

gness

The company who installed the boiler put the stuff in mine and I know the warranty still stands.

BRIGHT SPARK

Gness...have you had to claim on it yet?

gness

It's now out of warranty, BS but before I agreed I had it in writing that no more than two of these treatments would be acceptable before negating any warranty. I was prepared to try one treatment to prove to myself that there was a leak under the floor. Otherwise I was going to be paying for work with no guarantee that that was indeed the problem.
Now you may be right and I have been lucky not to have to claim. They may have found a loophole but I was in the fortunate position of being able to take that risk.

BRIGHT SPARK

Gness...anyone using fluid blockers such as Fernox, ect should be aware that they are a fine sludge, and if they block up a pipe leak they will also contribute to valve blocking within what is effectively a very precise and temperamental piece of equipment.

gness

Thanks, BS....the chap did explain why it can't be used more than twice but as no-one could tell me for definite that there was a leak under the floor it seemed the best way to confirm it and that has worked.
If it does start dropping pressure again I will have it repiped above the floor but at least I will know that it is going to fix the problem.....would be a bit sickening to have all that done and still have had the problem.