Why are my pipes making banging noises?

Banging pipes are one of the most common plumbing complaints, and the good news is the cause is usually identifiable. The most likely culprit is a phenomenon called water hammer — a pressure shockwave that travels through your pipes when water flow is suddenly stopped.

What is water hammer? When you shut off a faucet quickly, or when a washing machine or dishwasher valve snaps closed automatically, the moving water has nowhere to go. That sudden stop creates a pressure wave that slams against your pipes and fittings, producing that distinctive bang or thud. Modern plumbing systems use air chambers or water hammer arrestors to absorb this shock — if yours are waterlogged or missing, the banging gets worse over time.

Other common causes include loose pipe straps, which allow pipes to physically move and knock against joists or framing when water flows through them. You might also be dealing with thermal expansion in hot water pipes, which expand as they heat up and can creak or pop against tight brackets. In older Ottawa homes, high water pressure is another frequent cause — anything above 80 PSI can stress your pipes and amplify water hammer significantly.

In Ottawa specifically, homes with older galvanized or copper supply lines may experience more pronounced banging as pipes age and fittings loosen. If your home was built before the 1980s, it's worth having a licensed plumber assess the overall condition of your supply lines while they're investigating the noise.

When should you worry? Occasional banging is usually harmless, but persistent or worsening noise can signal high pressure that's stressing your joints and connections — which can eventually lead to leaks. If the banging is accompanied by visible pipe movement, reduced water pressure, or discoloured water, treat it as more urgent.

A plumber you hire can install water hammer arrestors (typically $200–$400 installed), adjust your pressure reducing valve, or re-strap loose pipes — all relatively straightforward fixes. If you'd like to get a local plumber's eyes on the problem, you can submit your details through Ottawa Pro Plumbing and get matched with licensed plumbers in the Ottawa area at no cost to you.