Low Pressure in Just One Tap: 6 Likely Causes & How To Fix
Every other tap in the house is fine. This one dribbles. It’s an oddly annoying fault, and it sends a lot of people down the wrong path entirely, ringing the water company or pricing up a pump they don’t need.
If the rest of the house is behaving, the problem is local. It’s the tap, its isolation valve, or the short run of pipe feeding it.
Why is the water pressure low in only one tap?
Because pressure at the main is shared by the whole house. If it had dropped, every outlet would have dropped with it.
So Severn Trent and your main stopcock go to the bottom of the list. What’s left is a restriction somewhere between the branch pipe and the spout, and there aren’t many places it can hide.
What are the six most likely causes?
1. A blocked nozzle or aerator. Limescale and grit collect in the little mesh at the end of the spout. This is the most common cause by a distance, and it’s the one we talk people through on the phone rather than charging them to come out. Unscrew the nozzle, soak it in white vinegar for a couple of hours, rinse it, put it back.
2. A partly closed isolation valve. Small screwdriver-slot valves under the sink get left half shut after a dishwasher fit, a new worktop, or any other job. Check both hot and cold. The slot should run in line with the pipe when it’s open.
3. Debris in the flexible connector’s mesh filter. Flexi tails often have a small filter in the end. Disturb the pipework anywhere in the house and bits of solder, PTFE and scale travel until something catches them.
4. A scaled or worn ceramic cartridge. This gives you poor flow without any drip, which confuses people. The cartridge is restricting the passage rather than failing to seal.
5. A kinked flexi. Easy to do when a sink is dropped in and the tails get pushed against the back of the cupboard.
6. A restricted branch pipe. A crushed pipe under a floor, a solder blob from an old joint, or a run of narrow galvanised iron that never got replaced. Genuinely possible, but much less common than the first four, so don’t start lifting floorboards yet.
How do I check tap pressure at home?
Use a one-litre jug and your phone timer on the kitchen cold tap.
Fill the jug and see how long it takes. Around 10 litres a minute is healthy for a kitchen cold. Under 6 litres a minute is poor. Clean the nozzle before you test, otherwise you’re just measuring the limescale.
Only ask a neighbour whether their water is weak if every tap in your house is affected. If it’s one tap, their answer tells you nothing.
Why is only my kitchen tap low pressure?
Kitchen mixers work harder than any other tap in the house, and they collect grit in the tails.
Start under the sink. Check both isolation valves are fully open, then look at the flexi tails and their filters. After that, the nozzle.
There’s another one specific to kitchens. Tall designer mixers, the sort with a swan neck and a pull-out spray, often need a decent minimum pressure to perform. Fit one to a house running gravity hot water from a loft cistern and it will underwhelm you forever, no matter how clean it is.
Why is my hot tap weaker than the cold?
That depends entirely on what system you’ve got.
On a gravity system with a cold water cistern in the loft, the hot side is fed by the height of that tank and it’s meant to be weaker than the mains cold. Nothing is wrong. That’s the design.
On a combi boiler or an unvented cylinder, hot and cold should be broadly comparable. If just one hot tap is weak, check that tap’s hot isolator, its filter and its cartridge.
If every hot outlet in the house is weak, the problem has moved to the boiler or the cylinder side, and that’s a different conversation. Anything on the gas appliance itself needs a Gas Safe engineer.
Will a new tap fix low pressure?
Only if the old fitting is blocked or restricted internally.
A new tap will do nothing for a partly closed isolator, a crushed pipe, or a system that simply doesn’t deliver much pressure. And fitting a mains-pressure mixer onto loft tank pipework will disappoint you just as much as the old one did.
Before anyone buys brass, it’s worth knowing which of the three you have: gravity fed from a loft cistern, combi, or unvented cylinder. We check that as a matter of course on jobs in Hinckley, Earl Shilton, Barwell and Leicester, because it changes what will actually work.
When is low pressure in one tap urgent?
When it appears suddenly and something else is off at the same time.
Take it seriously if:
- pressure drops away and your water meter is ticking with everything turned off
- there’s a damp patch, a warm spot on the floor, or a musty smell
- several taps start weakening over a few days
That combination can mean a leak in a floor or a wall, and the pressure loss is water going somewhere it shouldn’t. Ringing us at that point is a lot cheaper than ringing us once it’s coming through a ceiling.
A single weak tap that’s been slowly getting worse for a year, on the other hand, is almost always scale.
What to do first
Clean the nozzle. Check the isolators are fully open. Check the flexi isn’t kinked. That’s three jobs, no parts, twenty minutes.
If it’s still weak after that, we’ll find out whether it’s the fitting or the pipe, and tell you the price before we start. We cover Hinckley, Burbage, Leicester, Nuneaton, Coventry, Lutterworth and Market Bosworth.
Still dribbling after a nozzle clean? Call 01455 632 030.