Domakihub How to Fix Water Hammer and Stop Banging Pipes for Good
Diagnose the thud, choose the right fix, and know when to call a plumber.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
That loud thud or bang every time a tap snaps shut is called water hammer — a pressure shockwave that travels back through your pipes the moment fast-moving water is suddenly stopped. The video above shows plumbing expert Richard Trethewey install a water hammer arrestor step by step; the guide below walks you through diagnosing the root cause first so you apply the right fix. Whether you own a villa in Crete, manage holiday rentals in Mykonos, or run a boutique hotel in Athens, solving this early protects your pipework and keeps guests from being startled at midnight."
What Actually Causes Water Hammer
Water hammer happens when a valve closes faster than the flowing water can decelerate. Washing machines and dishwashers are the most common culprits because their solenoid valves snap shut in milliseconds, sending a pressure spike — sometimes exceeding 10 bar — slamming back through the supply line. Toilets with fast-fill valves, quick-shut ball cocks, and even modern single-lever mixer taps can all trigger the same effect.
A secondary cause is loose pipe supports. When a pipe is free to move inside a wall cavity or along a ceiling joist, the shockwave causes it to physically knock against the structure. In older Greek construction where copper or galvanised steel runs are held by corroded or missing brackets, even moderate pressure can produce a surprisingly loud bang.
Why Pressure and Pipe Age Matter in Greek Properties
Mains water pressure in Greece varies widely between municipalities and between the ground floor and the top floor of a multi-storey building. Anything above 5–6 bar (roughly 70–85 psi) dramatically worsens water hammer and accelerates wear on rubber washers, braided hoses, and valve seats. Many older properties in island villages and dense urban neighbourhoods have never had a pressure-reducing valve (PRV) installed — this is the single most impactful fix a licensed plumber can make.
Mineral-rich water common in the Aegean islands also causes calcium scale to accumulate inside stop valves and air chambers over time, reducing their effectiveness. If your property has hard water, plan to flush or replace air chambers every two to three years as routine maintenance.
5 Steps to Diagnose and Fix Water Hammer
- 1
Check your water pressure first
Attach a pressure gauge to the garden tap or washing-machine inlet (available at any plumbing supply shop for under €15). If the reading exceeds 5 bar, water pressure is almost certainly the root cause. At that point, call a licensed plumber to fit or adjust a pressure-reducing valve on the main supply entry — this one step often eliminates banging entirely and extends the life of every appliance in the building.
- 2
Flush and recharge the air chambers
Older plumbing relies on short capped stub pipes — called air chambers — near each valve to cushion the shockwave. Over months, water absorbs the trapped air and the chambers lose their cushioning effect. To recharge them, shut off the main stopcock, open the highest tap in the building, then open the lowest tap (or a drain cock) to empty the pipes completely. Close everything and turn the mains back on slowly. The pipes refill and air chambers reset. This costs nothing and sometimes solves mild cases immediately.
- 3
Secure loose pipe runs
Go to the area where the banging is loudest — often behind the washing machine, under a sink, or in an exposed ceiling run. Press your palm against the pipe while a helper turns a tap on and off sharply; you will feel the pipe jump if it is loose. Fit plastic or rubber-lined pipe clips every 60–90 cm on horizontal runs and every 120 cm on vertical ones. Use clips sized precisely to the pipe diameter so the pipe sits snugly without being crushed — a loose clip is nearly as bad as no clip at all.
- 4
Install a water hammer arrestor
A water hammer arrestor is a sealed device containing a piston backed by a pressurised nitrogen chamber. Unlike a simple air chamber it never becomes waterlogged. Fit one on both the hot and cold supply lines immediately behind the problematic valve — most washing-machine and dishwasher connections accept a standard 3/4-inch or 1/2-inch push-fit or compression arrestor that screws in without soldering. Turn off the supply, replace the braided hose connection with the arrestor in line, and restore water. This is a permanent fix rated to last the life of the appliance.
- 5
Replace fast-closing valves or worn washers
If the bang comes from a tap rather than an appliance, the culprit is often a deteriorated rubber washer or a cheap ceramic cartridge that closes too abruptly. Turn off the isolator valve under the sink or basin, dismantle the tap head, and inspect the washer — a flat, cracked or hard washer should be replaced with a correctly sized rubber one for under €2. If the cartridge is ceramic and shutting the tap produces a sharp bang every time, swap it for a quarter-turn cartridge rated for slow close. If you are unsure about dismantling valves on the main supply line, ask a plumber — it is a short, inexpensive job.
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FAQ
- Is water hammer dangerous or just annoying?
- It is both. The repeated pressure spikes stress pipe joints, solder connections, and rubber hoses over time. In severe cases — particularly where pressure is already high — water hammer can eventually rupture a braided supply hose or crack a push-fit joint, causing a flood. Holiday rental owners are especially at risk because a burst hose can go undetected for days. Treat persistent banging as a maintenance issue, not a nuisance.
- Can I install a water hammer arrestor myself or do I need a plumber?
- For appliance connections (washing machine, dishwasher) the answer is yes — it is straightforward DIY. You turn off the local isolator valve, unscrew the existing hose from the wall inlet, and thread in the arrestor followed by the hose. No soldering is needed. However, if the problem is in the mains supply line, inside a wall, or requires adjusting the pressure-reducing valve, call a licensed plumber (adeiodotimenos ydravlikos). Working on pressurised mains pipework without the right tools can cause a larger leak.
- My pipes bang only at night — why?
- Municipal water pressure typically rises at night when demand across the network drops. If your building has no pressure-reducing valve, the mains can push well above daytime levels after midnight, triggering water hammer in pipes that were quiet during the day. Fitting a PRV set to around 3.5–4.5 bar usually resolves nighttime banging entirely, and is a job for a licensed plumber who will also check that the setting meets Greek building regulations for your property type.