Skip to Content

Boiler Ticking Like a Clock? Top 5 Reasons (+ How to Fix)

Boilers provide much-needed warmth to a home, but there’s nothing enjoyable about a ticking boiler. You might be wondering if this constant noise is dangerous to your home, the plumbing, or the appliance. Boilers make plenty of noises due to the heat fluctuations, but it’s important to know what’s normal and what should be repaired.

Your boiler is ticking like a clock for one of these reasons:

  • Expanding water
  • Loose components
  • Mineral deposit buildup
  • Plumbing leaks
  • Trapped air

In this post, we’ll discuss a handful of reasons your boiler is ticking and whether or not they need to be addressed. We’ll also talk about what you can do to fix your boiler and reduce the noise as efficiently as possible.

Water Expansion

Water expands and contracts the boiler and its pipes. These small adjustments make the metal, PVC, and plastic components tick every so often. Superior MSI explains these minor noises are normal and aren’t typically a cause for concern. However, if the ticks get louder, it’s best to have them checked by a professional.

How to Fix

Since water expansion is natural, there’s not much you can do to stop it. The good news is that it’s expected, so you don’t have to worry about it causing additional damage.

Aggressive water expansion caused by rapid temperature fluctuations can worsen the wear and tear, though. To prevent this issue from occurring, you can insulate the boiler’s pipes with PVC or copper insulation. Ensure the manufacturer allows insulation before taking on the project to prevent warranty disruptions.

If the ticking gets louder, the water expansion might only be a fraction of the problem. This normal process can worsen ongoing plumbing concerns, so it’s worth reviewing the remaining possible causes below.

Loose Mounting Parts

Boilers often have nuts and bolts that prevent the unit from wobbling or falling over. Over time, the parts loosen and make room for rattling. You might hear a lot of clicking or ticking when the boiler is on, especially when it’s working harder than usual. A good indicator is if the ticking stops right when the boiler turns off.

How to Fix

Here’s what we suggest you do:

  • Locate and tighten all of the loose nuts and bolts. It’s easier to find them when the boiler is on since you can trace the rattling noises. These parts loosen from the boiler’s rumbling, so it’s important to tighten them every few months.
  • Use Loctite Threadlocker to lock all of the screws in place. Loctite is designed to hold screws and fasteners without rusting. It also prevents them from loosening, which drastically limits the ticking noises.
  • Replace stripped screws to prevent them from moving. Switching stripped screws is important because it prevents the noise, but it also stops the boiler from falling over. Consider drilling new pilot holes nearby if the previous drill hole is too wide or stripped.

Limescale Buildup in the Plumbing

According to Duffy Heating, limescale and other mineral deposits can cause a boiler to tick. Minerals form and pile up after long-term use. Hard water packed with calcium, magnesium, and other minerals will undoubtedly lead to ticking and other symptoms in a boiler. Failure to correct the issue can lead to expensive repairs.

How to Fix

Follow this process to eliminate limescale buildup:

  1. Turn off the power and water inlet valve going to the boiler.
  2. Mix one gallon of water with one gallon of white vinegar in a bucket.
  3. Attach a threaded hose to the boiler’s inlet and another threaded hose into the boiler’s drain.
  4. Shut the outlet valve to prevent the solution from flowing into the house.
  5. Open the water inlet valve and run the vinegar and water mixture through the boiler and out the drain until the solution is gone, then shut the valve.
  6. Reverse the process to restore the boiler (consider repeating it with two gallons of freshwater if you want to prevent the vinegar from steaming through the boiler).

If you prefer a video tutorial, follow this process:

Ticking Boiler Leaks

Water and steam leaks are additional causes of odd boiler sounds. If your boiler keeps ticking, there’s a chance that there’s a leak. Boiler leaks are like ticking clocks that eventually grow in size. The longer you wait to repair the leak, the worse it can get. A big boiler leak can disrupt the pressure exchange and limit the boiler’s heating capabilities.

How to Fix

If your boiler has plumbing leaks, try this:

  1. Replace all elbows, couplings, and straights with new PVC pipes if you have PVC plumbing. If your boiler uses copper plumbing, it’s best to hire a professional since it requires soldering.
  2. Add Teflon tape to every water gasket. Supply Giant’s Plumber’s Tape is a ¾” x 260” roll that you can use throughout the boiler’s threaded pipes. Ensure all of the gaskets are sealed and tightened, too.
  3. Replace all ripped or broken gaskets and seals. There’s typically a seal or gasket between any portion where two threaded parts that move the water connect.

Trapped Air Bubbles

Air can creep into a boiler through leaks, pressure relief valves, poor water flow, and many other sources. Home Tree details how trapped air bubbles tick, contract, and rumble a boiler. These movements create loud knocking noises. These knocks can send water back into the boiler, which can damage it quickly.

How to Fix

Air bubbles are to be expected, but they need to be dealt with regularly. If your boiler is ticking because of excess air bubbles, open the air relief valve. The air will flow out of the valve until water comes out. Once the water starts flowing through the valve, shut it.

If the boiler keeps getting too many air bubbles, it’s time to search for a leak. Anywhere the water drips in the plumbing is a leak. These spots invite small air bubbles into the system that cause noises, interrupt the water flow, and more.

Additional Boiler Resources

If you ever experience different boiler problems, some of our other boiler troubleshooting articles may be able to help:


  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

As an Amazon Associate, we earn from qualifying purchases. We may also earn commissions if you purchase products from other retailers after clicking on a link from our site.