Combi boiler

[Marymint]

The water gauge on my Combi boiler keeps dropping, and I have to top it up periodically. Does this mean I could have a leak in the system somewhere, and will this be a big job? The system is only 4 years old. Many thanks for your advice. Marymint.

[cruella]

Hi Marymint.
If the pressure tends to drop on a regular basis, then you probably do have a leak.
Check round the pipes of your radiators to see if there is any sign of water.
Could also be a fault with your boiler.
Not a big job, hopefully.

[New Judge]

It may also be a faulty expansion vessel.

Combi boilers operate on a "sealed system". This means that as the water heats in the heating circuit it has nowhere to expand into. For this reason an expansion vessel is incorprated into the boiler and is a vessel which is divided by an elastic membrane.

The membrane is strong enough to maintain the pressure in the system, but "gives" as the water heats and expands.
If it is beginning to fail it is no longer strong enough to maintain the pressure in the system and gives the impression that water is leaking away.

Unless you have disturbed your piping or radiators for any reason, a failed expansion vessel is a more likely explanation for your problem.

They can be replaced but it is a job for a plumber.

[Marymint]

Many thanks Cruella and New Judge. Marymint

[colin6789]

Does the gauge go up quickly when you top it up. Mine developed this fault and it turned out to be that the expansion tank refered to earlier had not been pumped up on the annual service by British Gas?. this is carried out using a modified car tyre foot pump with a longer air hose and a special adaptor to fit the tamk. If this has not been done recently it may one need pumping up.

[Marymint]

Thanks Colin 6789. Unfortunately my boiler has not been serviced at all. As I mentioned the whole system is only 4 years old, so I haven't bothered yet. All I know is that, from the start, I have had to top it up now and then. I suppose I should have it checked. If it is a leak I can imagine it could be tricky to track it down - unless there is a special gadget you can use! Thanks again. Marymint.