Why Are My Pipes Banging? A Quick Guide to Fixing 'Water Hammer'
You have just turned off the bathroom tap, or your washing machine has just finished its cycle, and suddenly you hear a loud, rapid banging echoing through your walls or floorboards.
It sounds like someone is hitting your pipes with a spanner.
Don't panic. While it can sound terrifying, this is a very common plumbing issue known as "Water Hammer" (or hydraulic shock). At Parallel Plumbing Solutions, we get calls about this from homeowners across Chislehurst and Bromley every week.
Here is our quick guide to understanding what causes that terrible racket, how you can try to fix it yourself, and when it’s time to call in the professionals.
What is Water Hammer?
Water travels through your pipes at a surprisingly high speed and under a lot of pressure. When you suddenly close a tap, or a valve shuts quickly (like in a dishwasher or toilet), that fast-moving water suddenly has nowhere to go.
It slams into the closed valve, creating a shockwave that travels back through the pipework. This shockwave causes the pipes to vibrate violently and hit against the wooden joists or walls they are attached to—creating that loud "bang."
Why Has It Suddenly Started Happening?
If you have lived in your home for years and the banging has only just started, it is usually down to one of three things:
Waterlogged Air Chambers: Older plumbing systems have vertical pipes called "air chambers" that act as shock absorbers. Over time, these can fill up with water and stop working.
High Water Pressure: If your local water pressure (supplied by Thames Water) fluctuates or is set too high, the water travels too fast, making the shockwave much more violent.
Loose Pipework: The brackets (clips) securing your pipes under the floorboards or inside the walls can come loose over time. When the shockwave hits, the unsecured pipe physically rattles against the wood.
The 15-Minute DIY Fix
Before you call us out, try "resetting" your home's air chambers. It is free, easy, and often solves the problem immediately:
Turn off your water: Locate your main internal stopcock (usually under the kitchen sink) and turn it completely off.
Drain the system: Start at the highest point in your house (e.g., the upstairs bathroom) and turn on all the cold water taps. Work your way downstairs, turning on all the taps, including the outside tap if you have one.
Wait: Let all the water drain out. You will hear some spluttering as the pipes empty. Leave them open for about 5 minutes. (This allows the air chambers to refill with air).
Turn it back on: Go back to the stopcock and turn the water back on.
Close the taps: Work your way back from the bottom of the house to the top, turning the taps off one by one as the water flows smoothly.
When to Call a Professional
If you have drained the system and the pipes are still banging, you likely have an issue that requires a professional fix. Ignoring severe water hammer can eventually cause joints to weaken and pipes to burst, leading to expensive water damage.
You may need a plumber to:
Install a modern Water Hammer Arrestor (a mechanical shock absorber).
Fit a Pressure Reducing Valve (PRV) to safely lower the incoming water pressure.
Lift floorboards to properly secure loose, rattling pipework.
Don't let noisy pipes keep you awake or damage your home. Danny & Ellis at Parallel Plumbing Solutions are experts at diagnosing and fixing tricky pipework across Chislehurst, Bromley, Sidcup, and the surrounding areas.
Call us today on 07867 360868 or 07793 499179 or Click Here to Contact Us to book an inspection.