Sudden drop in water pressure? Check whether it is just your house
A sudden drop in water pressure is only likely to be a leak on your own pipe if your house alone is affected and water keeps escaping with every tap off. So start next door. Ask a neighbour whether their taps have slowed too. If they have, the cause is most likely in the water company's network, such as a burst main or repair work.
Most water companies post burst mains, planned work and supply problems on their website, searchable by postcode, and you can ring them as well. Low pressure along a whole street is theirs to deal with, and it usually comes back once their repair is done. If only your home is affected, or the drop arrived with a wet patch outside, carry on with the checks below.
One tap or every tap, hot or cold
Next, work out where the drop shows. Start with the kitchen cold tap, because it is almost always fed straight from the mains, while in many older homes the bathroom taps come from a tank in the loft. If the kitchen cold tap runs strongly and one other tap is weak, the fault sits near that tap, not on the supply.
A single slow tap is a plumbing fix, not a leak. Limescale or grit often clogs the small filter at the spout, which you can unscrew and rinse; otherwise a worn cartridge or a small isolating valve under the basin, knocked half shut, is the likely cause. If only the hot side has dropped, ring a heating engineer, because the boiler or cylinder is the usual suspect.
One tap weak: a blocked filter, a worn cartridge or a half-closed valve
Hot taps weak, cold fine: the boiler, cylinder or loft tank
Every mains tap weak, neighbours fine: the stop tap or the supply pipe
The whole street weak: the water company's network
A stop tap that is not fully open
A stop tap left partly closed is easy to miss and costs nothing to put right. It happens after a plumber has been, after a new meter or kitchen, or when someone shut it in a hurry and did not open it all the way. Turn it anticlockwise until it stops, then back a little so it does not stick in the fully open position.
Old stop taps can also fail inside, so the handle turns but the valve barely opens. If yours is stiff, weeping at the spindle or makes no difference when turned, leave it rather than force it, and have a plumber replace it. The valve in the chamber by the outside meter is usually the water company's, so if you suspect that one, ask them to check it.
A split on the supply pipe
When the street is fine, the stop tap is open and every mains tap has dropped at once, a split on the buried supply pipe becomes the likely cause. That is the length running from the edge of your land, or from the meter, into your home, and it is usually the owner's responsibility. A split big enough to lower the pressure is losing a lot of water, so it pays to act quickly.
In older terraces in Norwich, Ipswich and Colchester the supply can still be lead or iron, sometimes shared with next door. On farms, cottages and barn conversions the pipe may run a long way along a track or across a field, often by a route nobody remembers. Newer homes usually have blue plastic pipe, which can still fail at a joint. Whatever the pipe, these are the signs to look for outside:
A wet strip or soft ground between the meter and the house
Water seeping up between block paving or through a gravel drive
Grass that stays greener along one line across the lawn
Testing with the meter
The meter gives the clearest answer. With every tap, appliance and hose off, lift the lid and watch the small dial or red wheel on its face. A split big enough to drop your pressure usually sets it spinning fast enough to see in a few seconds, very different from the slow creep of a dripping tap or a cistern.
Now close the stop tap inside the house. Check it is holding: the kitchen cold tap should slow to nothing within a few seconds. Turn that tap off again, then look at the meter. If the dial has stopped, the water is escaping indoors, so check under sinks, the airing cupboard, the loft and any ceiling below a bathroom. If it keeps turning and the meter is outside, the loss is on the buried pipe between the meter and your stop tap.
If your meter is indoors, it cannot see the buried pipe at all, because the water escapes before it reaches the meter. A sharp pressure drop with a still indoor meter can therefore still be a supply pipe leak. With no meter at all, the drop itself and any wet ground outside are the clues to go on.
Who to call: us or the water company
Ring the water company if the whole street has low pressure, if water is bubbling out of the road or the footway, or if the meter or its fittings are leaking. Their pipe usually runs as far as your boundary or the meter, and looking after it is their job. Ring us when the leak is on your side: the meter keeps going after you close the stop tap, the wet ground is between the meter and the house, or the company has written to say the leak is yours.
We trace the buried pipe from the surface. On most supply pipes that means acoustic listening: a ground microphone picks out the noise of water leaving the pipe as we follow its line. Tracer gas, a hydrogen and nitrogen mix, takes over on plastic pipe and quiet leaks. The point is confirmed with a second method, then marked and photographed. Digging starts at the mark, and nobody can be sure of the leak until that piece of pipe is uncovered.
We can usually mend the pipe while we are there, quoted separately, and repairs are guaranteed for 3 months on the pipework and fittings we install. No find, no fee on home water leaks covers one leak on a water main up to 30 m or the hot and cold supply pipes, at least half a litre a minute, where we also carry out the access and repair. It does not cover central heating, shared mains, businesses or leaks that come and go. Full conditions are on our terms page.
What to tell your insurer and the water company
Before you book, look at your home policy for two things: cover for the underground supply pipe, and trace and access cover, which some insurers offer for tracking down a hidden leak and getting to it. Ask, too, whether your insurer must approve the firm doing the work. Pay for the visit in full and the written report comes to you, with the location, methods, readings and photographs. What the insurer pays, if anything, is their decision.
Each water company has its own leak policy, and some may reduce a bill that a supply pipe leak pushed up, once the pipe has been mended. The rules differ from company to company, so ask yours before the repair and keep the report and your receipt. We cannot promise what they will decide, but the report records where the pipe failed and the methods that found it.