If your pipes bang in the walls when you turn off a tap or the washing machine cuts off, that is water hammer — and it is quietly working its joints loose. Here is what causes it and how to actually stop it.
What water hammer is
When fast-moving water is stopped suddenly — by a quick-closing mixer, a washing-machine or dishwasher solenoid valve — its momentum has nowhere to go and slams against the pipes and fittings. High municipal pressure amplifies the shockwave, which is why it often sounds like a hammer in the walls.
Why it matters
It is not just noise. Each shock loosens joints, stresses fittings and, over months, causes drips, leaks and the classic burst flexi-hose under a basin. Left unchecked, water hammer shortens the life of your whole plumbing system.
The fixes that work
- Reduce the pressure — a pressure reducing valve set to a safe level is the single most effective fix where high pressure is the root cause.
- Fit water-hammer arrestors — small shock-absorbing devices near the offending appliances (washing machine, dishwasher).
- Secure loose pipes — clipping pipes that are free to move stops them banging against the structure.
Worse at night?
Municipal pressure usually rises overnight as demand drops, so hammer is often loudest then — a strong sign that pressure is the culprit. We diagnose which combination of fixes your home needs. Book a check or read about pipe repairs.