Right, back boilers are usually known for trouble-free, long lives. Although they might now be frowned on by an energy-conscious government which virtually insists on highly efficient condensing boilers, a good back boiler will do the business.

But, there’s always the exception.

My back boiler is situated in our top-floor maisonette and provides water for the hot water taps and the central heating system. It runs off coal and is reasonably good at providing a fair degree of heat, as long as it’s stoked up. You keep the coal-fire banked up and the heat efficiently heats up the water in the back boiler. Okay, so a lot of the heat escapes up the chimney, but this type of boiler is simple to use.

A thermostat sits near the fire in the lounge and the system has for many years behaved itself.

Unfortunately, for some time the thermostat had been stuck and this was causing the water to overheat. I wasn’t aware of this, nor of the unfortunate side effect: black silt which was leaking out from the boiler pipes in the airing cupboard.

And it didn’t stop there. The black silt had proceeded to work its way from the cupboard, down the walls and into the property below. And bear in mind that this silt is much like black treacle. Once dry, it effectively ruins anything it touches.

Only when the neighbour came to discuss the source of the black sludge rivers running down his wallpaper did we trace the source back to my airing cupboard, and then my boiler.

Fixing the problem was quite simple. A heating engineer swapped the faulty thermostat, the boiler stopped over-heating and everything went back to normal, apart from the redecoration that was needed to my airing cupboard and the neighbour’s walls.

But it just goes to show that once in while, even if you have your annual boiler and heating system service, it’s worth giving your kit the once over.

And one other thing about back boilers I discovered. Technically, they are now viewed as inefficient and potentially lethal. Although they break down considerably less than a conventional boiler, they have been shown to be responsible for more carbon monoxide leaks. They are potentially more dangerous than other boilers, but if you service regularly and keep an eye on them, then the worse should not happen.

When I chatted to the heating engineer about when the day came for my back boiler to be replaced, he did say that new building regulations now insisted on the installation of a highly efficient condensing boiler, unless that was impractical. In other words, a condensing boiler requires an outside wall for the siting of the flue and drain system. My maisonette’s kitchen wouldn’t allow that, so I can once again install a coal-fired back boiler.

And just in case you’re wondering, a condensing boiler is over 90% efficient, saving fuel costs and carbon dioxide release, because it not only uses the heat from the initial burning of the fuel source, but also takes the heat from the exhaust gases. Hence it needs an outside situated flue and special drains to take away waste fluid which is generated by the use of the exhaust gases.

But, whichever boiler you have, just remember that one key lesson: don’t ignore it. Just because you think it’s working properly, doesn’t necessarily mean it is.

Guest Article by Neil Camp