Low water pressure is one of those problems that creeps up slowly or arrives overnight, and the cause ranges from a half-closed valve you can fix in seconds to a job for the water company. Working through it in order tells you which one you are dealing with.
Is it every tap, or just one? Whole-house low pressure points to the supply or stop tap; a single weak tap is almost always that tap.
One Tap, or the Whole House?
- Just one tap or shower
- Almost always a blocked aerator or limescale at that outlet, or a partly closed isolation valve under it - a quick, local fix.
- All hot taps weak
- Points to the hot water side - a cylinder, combi or airlock issue rather than the incoming main. See no hot water checklist.
- Every tap in the house
- That is the incoming supply: the main stop tap, a pressure-reducing valve, or a problem on the water company's side.
The Checks To Run
Find your internal stop tap and make sure it is turned fully anticlockwise - a partly closed one throttles the whole house.
If there is an external stopcock at your boundary, check it is fully open too, especially after any recent work.
Unscrew the little mesh nozzle on the weak tap, rinse out the limescale and grit, and refit it. This fixes a surprising number of "low pressure" taps.
The small valves on the pipes under sinks and behind the toilet can be knocked half-shut - turn them fully on.
Common Causes
- A stop tap or isolation valve not fully open
- Limescale in the aerator, shower head or pipework
- An airlock in the system after the supply has been off
- A failing pressure-reducing valve or shared supply at peak times
- A hidden leak dropping the pressure - watch for damp patches
When It’s Not You
If the pressure is low at every tap, you have checked the stop taps, and neighbours report the same, it is the water company's network - contact them, as there is nothing a plumber can change on your side. A sudden total loss of pressure across the area usually means a burst main they are already working on. A slow long-term decline that is only your house, though, is worth a plumber's eye for a hidden leak or a failing valve.
If low pressure comes with no hot water specifically, our no hot water checklist narrows it down. For anything that needs a plumber, the emergency plumber cost guide covers rates - and if a pipe has burst and pressure has dropped suddenly, get an emergency plumber on the way.