Noisy Water Pipes? What Each Sound Means and the Fix

First, when does the noise happen?

The timing tells you more than the sound itself. Run through these questions before anything else, and write the answers down if you end up calling someone, because they save a lot of time on the visit.

• Only while a particular tap is running: the cause is usually on that outlet or the pipe feeding it.
• Whenever any tap runs, hot or cold: think pressure, the stopcock or a valve on the main supply.
• Only on the hot side: think the cylinder, the combi, air in the hot pipes or expansion as they warm up.
• After a toilet flushes or a washing machine fills: a float valve or an appliance valve refilling.
• With everything turned off: water is moving somewhere it should not be. Treat that as a possible leak.
• At night, in a quiet house: often a cistern that is slowly passing water, or a loft tank topping itself up.

Whistling or squealing pipes

A whistle is water being forced through a gap that is too small. The usual culprits are a stopcock or isolating valve that is only partly open, a worn washer or cartridge in a tap, or a float valve in a toilet cistern or loft tank that is nearly shut as the water level rises. If the whistle only happens while a cistern refills, the float valve is the answer, and replacing it or its washer ends it.

If the whistle happens whenever any tap is open, check the stopcock is fully open and any small isolating valves under sinks are lined up with the pipe. A valve left half turned after a job is a common cause. Our guide to where is my stopcock shows what to look for. Where the whistle sits near the incoming main and has got worse over time, a pressure reducing valve on that supply can also sing as it wears.

Humming or vibrating pipes

A low hum or buzz that you can feel in the pipe usually means water is moving fast through a run that is free to resonate. High mains pressure is the most common reason, especially in parts of London where the supply comes in well above what a house needs. Partly closing the stopcock as a test will often quieten it, which tells you pressure is involved. Do not leave it half closed, because combi boilers, unvented cylinders and showers need the full flow.

Humming that starts and stops on its own, with no tap in use, is often a pump. A shower pump, a booster set or the small pump that keeps hot water circulating round a large house can all hum through the pipework when their mountings wear or they start to fail. If you have a pumped hot water loop, our guide to a secondary return pump not working covers the signs.

Rattling and knocking

A rattle along a length of pipe while water runs is nearly always a pipe that is not clipped, knocking against a joist, a floorboard or the back of a kitchen unit. Put a hand on the pipes you can reach while someone runs the tap. Any run you can push more than a few millimetres needs clipping or packing.

A single loud bang or thud when a tap or appliance shuts off is different. That is water hammer, a pressure shock from water being stopped suddenly, and our guide to water hammer goes through the causes and the fixes that stop it for good.

Gurgling or spluttering pipes

Gurgling in the water pipes, together with taps that spit and cough before running smoothly, means air has got into the system. It is very common after the water has been turned off for a repair or by the water company, and it usually clears once each tap has been run for a minute or two, starting with the lowest tap in the house. If the hot taps keep spluttering, or a tap stops altogether, our guide to an airlock in hot water pipes explains how to clear it safely.

On an older house with tanks in the loft, gurgling that keeps coming back can mean the cold water tank is running low and drawing air, or that hot water is pushing up the vent pipe into a tank. Our guide to a header tank overflowing covers that second problem. Gurgling from plugholes and drains is a separate thing: that is the waste side, not the water supply.

Ticking and creaking when the hot water runs

Copper grows slightly as it warms. When you run a hot tap or bath, the hot pipes expand and slide against notches in joists or tight holes in walls, and you hear ticking and creaking that fades once the pipes settle, then returns as they cool. It is harmless. The fix, where it bothers you, is a little slack at the point where the pipe rubs or a sleeve where it passes through timber.

If the noise comes from the cylinder or boiler itself rather than the pipes, it has a different set of causes. Our guide to a hot water cylinder making noise explains which sounds are scale and which mean switch off now.

Hissing with everything turned off

A constant hiss or the sound of running water when no tap, toilet or appliance is in use means water is moving through the pipes. Sometimes the cause is harmless and visible, such as a toilet cistern passing water into the pan or a loft tank topping up after a slow leak from a float valve. Often it is not visible at all.

A simple test helps. Turn off every tap and appliance, then look at the water meter if you have one. If the dial is still moving, water is going somewhere. If the reading has changed after an hour with nothing used, and no cistern is running, you probably have a hidden leak under a floor or inside a wall. That needs finding before it damages ceilings and floors, and it is exactly what our leak detection and repair service is for.

If the hiss comes with a damp patch, a drop in water pressure, or water appearing through a ceiling, turn the water off at the stopcock and call us. A pinhole leak can run for weeks before it shows, and the longer it runs the more it costs to put right.

What we check on a visit

We start by listening for the noise with you and noting when it happens, then check the incoming pressure, the stopcock and every valve on the main runs, the float valves in cisterns and tanks, and any pumps on the system. Where a leak is suspected we test the supply and trace it rather than guessing where to cut. If the pressure is too high, a pressure reducing valve on the incoming main is often the lasting fix, and most rattles are cured with clips and packing in the same visit.

When to call us

Call us on 020 4652 5111 or send an enquiry if the noise comes with hissing when nothing is on, a moving water meter, a damp patch or a sudden change in pressure, or if you have tried the checks above and the noise is still there. We have 20 engineers across London, and our rate is on the pricing page, agreed before anyone attends.