What is water hammer and how do I fix it?

Water hammer is that loud banging or knocking sound you hear in your pipes when you quickly shut off a faucet or when appliances like washing machines or dishwashers suddenly stop the water flow. This jarring noise occurs when fast-moving water is forced to stop abruptly, creating a pressure wave that reverberates through your plumbing system.

The sudden pressure change causes pipes to vibrate and bang against wall studs, floor joists, or other pipes. While annoying, water hammer can also damage pipe joints, fittings, and appliances over time if left unaddressed. The problem is particularly common in Ottawa homes with older plumbing systems or high water pressure from the municipal supply.

Common causes include loose pipe mounting brackets, missing or failed air chambers (small vertical pipes that act as shock absorbers), waterlogged pressure tanks, or excessively high water pressure. Modern homes should have water hammer arrestors - small devices that absorb the pressure shock - installed near appliances and fixtures that create sudden water stoppage.

Simple fixes you can try include checking that all pipes are properly secured with mounting straps, especially in basements and crawl spaces where they're accessible. You can also try draining your plumbing system by shutting off the main water valve and opening all faucets to restore air chambers, then turning the water back on. If your home has a pressure tank, it may need to be recharged with air.

However, persistent water hammer often requires professional attention. A licensed plumber can install proper water hammer arrestors, adjust water pressure regulators, or secure loose pipes within walls. In Ottawa's older neighborhoods, this issue frequently coincides with aging galvanized pipes that may benefit from upgrading to modern PEX or copper systems.

Don't ignore ongoing water hammer - the repeated pressure shocks can eventually cause pipe joints to fail, leading to costly water damage. For a proper diagnosis and permanent solution, consider having Ottawa Pro Plumbing assess your system and install appropriate water hammer prevention devices.