Leaking Boiler

Do you have a leaking boiler?

If you have a boiler that you may think is leaking, but cannot see any form of leak, what do you do?

First we need to establish what type of boiler you have, is it a combination boiler, system boiler or heat only boiler.

With combination and system boilers they work under high pressure, with heat only boilers they are sometimes are pressurised, or work under low pressure.

With all boilers that are pressurised there will be a pressure gauge fitted to either the front of the boiler or close by on the pipe work.

A leaking boiler is not always a leaking boiler, I know that might sound strange, but it’s true. All these boilers working under high pressure should have an expansion vessel fitted either internally or externally, this is normally the cause of a leaking boiler.

So how do we resolve the leaking boiler problem?

First you should have your boiler serviced each and every year without fail, if you decide not to have your boiler serviced then at sometime in the future you will have an expensive repair bill or even the cost of a new boiler.

So why is it important to have your boiler serviced?

The days of not bothering to service your boiler have long gone, these boilers were very basic and not much went wrong with them, the most common problem was that the thermal coupling had to be changed. These boilers were not very efficient around 40% of your fuel bill went out of the flue and the other 60% into you’re heating system.

Since the introduction of the high efficiency condensing boilers it’s been very important to have them serviced each year. These boilers are built to give the best performance and most of all save you on your energy bill.

When a boiler service is carried out we are looking first to make sure everything is still safe, that there are no combustion or gas leaks, checking over the flue making sure the product of combustion are exiting to the outside as they should.

We take a combustion reading with a combustion analyser and check that the boiler when running is within the boiler makers parameters, if the reading are not correct then we carry out further investigation to find out why, then reset.

Next we come to the most common problem with these boilers.

The expansion vessel, The expansion vessel is a very important part of your boiler and heating system, if this is not working properly then you will have problems. The most common problem will be the loss of system pressure, most people describe this as a leaking boiler.

In fact it’s not a leaking boiler, it’s an expansion vessel problem. The vessel needs to be checked each year and reset for your boiler to give its best performance, when the vessel it not checked, over time it will stop working.

The Boiler Service

When you call in your local gas safe registered boiler service engineer to service your boiler, ask him to make sure the expansion vessel is checked over and reset if needed. For some reason when a boiler service is carried out, the expansion vessel seems to be left out and not checked, not all of the time but around 80% of the time. When you read the boiler makers instructions on boiler service they state that the expansion should be checked and reset if needed.

So what happens to the expansion vessel?

The best way to describe the expansion vessel is, its like a car tyre, over time it will eventually go flat. The vessel is the same, it is pumped up with a car pump to a Pressure that is compatible to the type of heating system you have.

If the vessel loses its pressure then it will start to fill with water internally, once this starts to happen most people start to think they may have a leaking boiler.

The expansion vessel works by taking up the expansion of the water as it heats up within you’re heating system. If the vessel has no internal pressure then it will fill up with water, once full, your boiler will then start to discharge water through the pressure relief valve, to release the pressure to stop pipes bursting.

So do you have a leaking boiler or a flat expansion vessel?


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