Top 5 Most Common Boiler Problems

Boilers are a home appliance that everyone has, everyone uses, and few know much about. They are one of those things you never notice until it breaks. So to shed some light on this vital instrument that heats your home’s water, and to help you fix it, we’ve put together this quick-and-easy troubleshooting guide.

Boiler Basics

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Boilers are divided into two main groups: those with tanks and those without. Both types are available in either gas or electric. Tankless heaters have become popular in recent years for several reasons. They are more energy efficient, take up much less space, never ‘run out of hot water’ like traditional heaters, and heat water almost instantly, so you wont have to wait for the shower to warm up. Their primary disadvantage, however, is that they limit water flow because they must pump it through very narrow pipes in order to quickly heat it. For this reason, tankless heaters are typically not a viable option for households that require large amounts of water.
Cost is another matter to take into account. Tankless boilers typically cost at least twice as much to initially purchase and install. But they can also cut energy bills by up to half.
As for the gas/electric distinction, the main difference is that electric boilers are cheaper but less efficient, while gas heaters cost more initially, but enable significant long-term energy savings. Some gas units are even eligible for tax breaks.

Common Problems and Solutions

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The following applies primarily to tank boilers, which are more common and more likely to break down. But they are also easier to fix as the modern tankless boilers require technical knowledge and can usually only be worked on by professionals.

Loss of Pressure

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The pressure on a traditional boiler should be somewhere between 1.0 and 1.5. If your pressure declines sharply, it might mean that you have a leak or a breached pipe. If it suddenly increases, you probably have a blockage. But the much more common issue is a gradual pressure decline, for which the fix is quite simple. Turn off the boiler, locate the nearby filling loop (usually a copper hose), and add water slowly to the system until the pressure returns to between 1 and 1.5.

Water Leaks

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If water is pooling at the base of your boiler, it likely means one of three things: the Temperature and Pressure Relief Valve is faulty and needs to be replaced, the tank has corroded and needs to be replaced, or a pipe has corroded and needs to be replaced. Simply find the leak, replace the faulty part, and the problem is fixed (hopefully).


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A blockage is one of the worst things that can happen to your boiler. It can be caused by sediment buildup, corrosion, or a number of other unpredictable fateful accidents. If there is a sudden inexplicable loss of heat or sudden abnormally high pressure, the best you can do is to shut off the boiler and call a professional. Make sure that the repairman is Gas Safe Registered.

Rust Colored Water

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An alarming issue, indeed––this is usually caused by corrosion inside the tank precipitated by a failure of the Sacrificial Anode Rod¬¬––which, as you might have guessed from it’s name is inevitable in old boilers. Replacement anodes are available in most plumbing supply stores and are easily swapped out.

Rotten Egg Smell

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This problem is also usually caused by a failed Sacrificial Anode Rod, which can allow hydrogen- and sediment-feeding bacteria to form. After replacing the rod, you will need to flush the heater with a solution of 2 pints hydrogen peroxide and 40 gallons of water. Let it set in the tank for 2 hours before running the water and clearing the tank. If the smell persists, try switching to a zinc-alloy anode rod.
Luckily, traditional water heaters are quite mechanically simple, and are often easily fixed by anyone possessing basic handyman skills. Now that you are oriented in the basic ins-and-outs of boiler anatomy and repair, you’ll know just what to do if the faucet starts spitting out dirty water or the garage suddenly begins smelling of old eggs.
Many thanks to the team at Staunch and Flow for putting together this article; Specialising in Boiler Repairs in London they hope this guides you to identifying a boiler problem and remember to always seek help from the professionals, do not take the risks yourself to fix!