Easy Fixes for a Noisy Boiler

September 18, 2015

Boilers can emit loud and worrying rattles and bangs — but they don't mean it's about to explode. There are a few things you can do before you call in the professionals.

Easy Fixes for a Noisy Boiler

What is making that racket?

Check the temperature control and fill the system

  • The water in the boiler may be getting too hot and turning to steam. Try turning the temperature control on the boiler down a bit and see if the noises stop.
  • If you have an open-vented heating system, check that there's water in the expansion tank in the attic — if there's no water in the tank, turn off the boiler immediately. Has the float valve on the expansion tank corroded and stuck in the closed position? If you cannot free it, call a professional to install a new valve. If you have a sealed heating system, check that its pressure gauge shows the desired reading (consult the user's manual for your model); if not, refill the system to the correct pressure following the manufacturer's instructions. If the problem persists, call an engineer to check for leaks in the system.
  • Loud bangs are often caused by lime in the boiler. With time, lime can get baked onto the sides of the boiler causing localized hot spots where steam bubbles form and make knocking or "kettling" sounds as they rise. This can be reduced by adding specialist descaling fluid to the system; you can buy this from a home improvement store or plumbing supply store. Be sure to follow the manufacturer's instructions. You will need to add the fluid, run the system to allow the fluid to work, then drain, flush and refill the system. This is a job best left to a professional unless you are very confident with plumbing projects.

Know your boiler

There are two prevalent designs of heating system — open-vented and sealed. To fix many heating problems, you need to know which you have in your home.

Open-vented heating systems

Open-vented systems include a small water tank, usually in the attic. This tank gives the water in your system enough room to expand when heated (preventing burst pipes); it's also where you refill your system with water.

Sealed heating systems

These systems are more common in apartments where there's no space for an expansion tank. Instead, they have an expansion vessel and are filled via a flexible pipe — the "filling loop" — that joins the heating system to the main cold-water pipe.

Make it last

  • Add liquid inhibitor to your heating system every four to five years. The steel components of a system will corrode over time, depositing particles of rust inside your boiler, pipes and radiators. Adding inhibitor will slow this reaction, making your heating more efficient and extending its life. The type and amount of inhibitor needed, and how it is applied, will depend on the type and age of your system; consult a professional for advice.
  • Be sure to have your boiler serviced annually — you'll prolong its working life and save money on fuel.
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