To find out why your water pipes bang when you shut off a Faucet, we’ll go over 7 possible causes, how to fix the issues, and when to call a plumber.

So, why do your water pipes bang when you turn off a Faucet?

It’s probably due to the noise caused by water hammer (a common issue), but could also be because of loose pipes, or high water pressure.
Additionally, bad Valves, or the way some of your household appliances work can also create banging noises.

Knowing why your pipes bang will help you protect your plumbing system. Below are 7 different common causes as well as ways to prevent the issue.

1. Water Hammer

Water hammer is another name for the banging of water pipes. Water hammer is created when the water flow has stopped in a pipe.

Each time you rapidly turn a Faucet off, the rapid change in water flow creates a pressure wave that goes through all the piping. That pressure wave is likely to shake the pipes and create banging.

Depending on the length of piping and location where you heard the noise; there may be one big thud, or multiple smaller knocks.

A plumber can install a water hammer arrestor which is essentially a device designed to absorb the excess energy/pressure that would normally create the pressure wave and subsequent banging.

2. Loose water pipe straps & brackets

Loose support straps or broken pipe hangers can allow the water pipes to move slightly when water is flowing.

These slight movements may result in hitting walls or joist located nearby. These impacts commonly produce banging or knocking sounds when you turn faucets on/off, etc.

A plumber can inspect accessible portions of piping to see if there are any loose areas and tighten or even replace them. Additionally, he/she can inspect any damaged bracketing/hangers that may be causing additional piping motion.

3. Excessive water pressure

Having extremely high water pressure can increase the amount of tension on your entire plumbing system. In addition to making banging noises seem more prominent when closing taps or stopping appliances from filling; it could lead to: leaks, cracked/damaged fixtures, reduced life expectancy of appliances.

A plumber can determine if your home has excessively high water pressure via a pressure gauge. If so, installing a pressure reducing valve could alleviate the pressure.

4. Faulty faucets & Valves

Faulty Faucet components and/or malfunctioning Valves can create rattling, vibration or banging noises. Some of the typical reasons for these types of problems include: worn cartridge(s) within the Faucet, loosened o-rings/washers on various Faucet components, worn-out/shabby valve components.

Determine which Faucet is producing the noise. Is it just one specific Faucet or many? If it’s one then it might be that Faucet itself or perhaps the shut-off valve leading to that Faucet. If it’s many then it could potentially be throughout your entire plumbing system. Replace the worn components on individual faucets. If many faucets are producing similar banging noises, consider having a plumber look at the larger plumbing system.

5. Washing Machines & dishwashers

In addition to banging pipes from faucets and toilets, Washing Machines and dishwashers can produce banging pipes. Both Washing Machines and dishwashers utilize an automated valve that opens/closes depending upon operation.

When an auto-valve shuts off quickly it creates a rapid change in pressure. This sudden pressure change typically produces banging behind a wall, within a cabinet or near the appliance.

Consider timing when you hear the banging. Does it occur while an appliance is being filled? If so, this could mean either a solution exists for both the appliance itself and its associated fill line/supply hose/supply pipes. Consider consulting a licensed plumber.

6. No/wrong size water hammer arrestor installed

Water hammer arrestors help soften the blow when water is rapidly stopped in piping. By absorbing the impact when water is halted abruptly; they eliminate much of the pressure surge generated by the abrupt closure of an auto-shut off valve.

Banging is most probable if an arrestor is non-existent or damaged in systems utilizing an auto-shutting valve such as Washing Machines or other appliances requiring quick-shut-off Valves.

A licensed plumber will assess if your current plumbing system requires an arrestor installed or replaced when necessary.

7. Thermal expansion – piping movement caused by heat of hot water

As water gets hotter than ambient temperature; piping expands proportionally based on temperature rise. As piping heats-up, it may begin rubbing against wood framing elements/building material(s).

Piping movement may generate audible clicks/pops/bangs as piping moves back-and-forth with each usage of hot water; i.e., shower usage or post-washer hot water runs.

There are two ways to minimize friction: provide adequate spacing for free-motion of piping and use proper bracing/supports for piping installation.

Are you concerned about your noisy water pipes?

Here are several things you can do to help reduce potential future issues and diminish ongoing plumbing noise:

– determine which Faucet(s)/fixture(s) produce(s) the banging noise
– identify type of water used (hot vs cold)
– test your home’s water pressure using a pressure gauge
– consult with a plumber regarding inspecting loose pipe(s) and/possible bad valve(s).
– discuss installing a water-hammer arrestor if pressure surges appear to be creating the banging
– schedule inspections if banging persists, grows louder, or varies based on differing operational conditions (e.g., washer/dishwasher).

Don’t ignore continued pounding or clanking of your pipes. It could signal a problem needing immediate assistance from a professional plumber.

How can you tell when to contact a licensed plumber?

While occasional plumbing noise may have a logical explanation; repeated or intense banging should receive prompt investigation.

Recurring water hammering along with extreme water pressure stress may eventually compromise pipes/fittings/fixtures and lead to future plumbing failures.

Call a licensed plumber immediately if you:
• cannot identify source of banging
• find banging occurring simultaneously among multiple fixtures
• see signs of previous leaks or observe unusual changes in water pressure