If the pipes in a building bang or knock when a tap, flush valve or washing machine shuts off, that is water hammer. In Dubai and across the UAE it is common in villas, towers and hotels, where high mains pressure and fast-closing valves meet long pipe runs. A water hammer arrestor is a small device that absorbs the shock and stops the noise before it damages the system.
What causes water hammer?
Water moving through a pipe has momentum. When a valve closes quickly, the water stops suddenly and the pressure spikes, often several times above normal working pressure. The pressure wave travels back and forth along the pipe, which is the bang you hear. Solenoid valves, quarter-turn valves, flush valves, dishwashers and washing machines are the usual triggers.
Why it matters
- Repeated pressure spikes loosen pipe supports and joints.
- Valves, mixers and appliance hoses wear out faster.
- Leaks can start inside walls and ceilings, where they are costly to repair.
- The noise itself causes complaints in apartments and hotels.
How a water hammer arrestor works
An arrestor has a sealed chamber with an air or gas cushion separated from the water by a piston or bellows. When the pressure wave arrives, the cushion compresses and absorbs the energy, then pushes back gently. Unlike a simple air chamber, a sealed arrestor does not lose its cushion over time.
Sizing basics
Arrestors are sized by the number and type of fixtures on the branch they protect. A single washing machine or sink needs a small unit, while a battery of flush valves in a washroom needs a larger one. Consultants usually show the size on the plumbing drawings; if not, send us the fixture list for each branch and we will suggest sizes.
Where to install them
- As close as possible to the quick-closing valve, ideally within the last few metres of pipe.
- At the end of long branch lines serving several fixtures.
- Upstream of solenoid valves on irrigation, water features and equipment.
- On washing machine and dishwasher connections.
They can be installed vertically, horizontally or at an angle, and in accessible locations so they can be checked during maintenance.
Materials
Alphatek supplies water hammer arrestors in brass, copper and stainless steel in a range of sizes. Stainless steel is a good choice for exposed or demanding locations; brass and copper suit most concealed domestic installations. See our water hammer arrestors page for details.
Frequently asked questions
Do water hammer arrestors need maintenance?
Sealed piston and bellows types are designed to work without regular recharging. They should still be accessible so they can be inspected or replaced if the building is refurbished.
Can I fit an arrestor to an existing building?
Yes. Arrestors are often retrofitted in Dubai apartments and villas where banging pipes cause complaints. They are fitted near the valve that causes the shock.
Do you supply outside Dubai?
Yes, we deliver across the UAE, including Abu Dhabi, Sharjah and the Northern Emirates.
Request a quote – send your BOQ, drawings or sizes and we will reply with options and a price, with delivery across Dubai and the UAE.
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