A banging or whistling boiler is called “kettling” and is usually caused by limescale buildup.
What Causes It? Limescale on the heat exchanger restricts water flow and causes overheating.
Step 1: Add a central heating descaler to your system — pour into the feed and expansion tank.
Step 2: Run the heating for several hours to circulate the descaler.
Step 3: Flush the system by draining and refilling.
Step 4: Add central heating inhibitor to prevent future buildup.