Why is my water pressure low?

Work out first whether it is everywhere or somewhere. That single distinction eliminates most of the possibilities and it is something you can determine in five minutes before anyone charges for their time.

One outlet only

• A blocked aerator on the tap spout, which unscrews and rinses out.
• A partially closed isolation valve under the fixture, often knocked while something was stored in the cabinet.
• A failing mixer cartridge, which typically affects hot and cold differently.
• Debris trapped after recent work upstream, which is common after a main was shut off and reopened.

Whole house

• The main tap at the meter not fully open, which happens after any work on the property.
• A pressure limiting valve at end of life. These have a service life and they fail closed as often as open.
• A leak on the supply side, which usually shows up on the bill before it shows up as a puddle.
• Works or a fault on the water authority's network, which is worth checking before booking anyone.

Hot water only

If pressure is fine on cold and poor on hot, the cause is in the hot water system rather than the supply. On older gravity fed systems that is normal by design. On a mains pressure system it usually means a tempering valve, an isolation valve or a scaled outlet.