One faucet trickles. Everything else in the house is fine.
That pattern is good news. When the problem is confined to a single fixture, it is a blockage at that fixture, and the fix is usually twenty minutes and no parts. Whole-house pressure problems are a different and more expensive conversation.
Work through it in order, cheapest first.
First, Confirm It Is Only One Faucet
Run the taps in every bathroom, the kitchen, and the laundry. Hot and cold separately. The pattern tells you where the problem is before you touch a tool.
| Pattern | Where the problem is | Fix |
|---|---|---|
| One faucet, hot and cold both weak | Aerator, cartridge or that fixture’s shutoffs | On this page |
| One faucet, hot only | Hot shutoff, or sediment in the water heater | Check the angle stop first |
| One faucet, cold only | Cold angle stop partly closed | Open it fully |
| Every fixture in the house | Regulator, main line, or the supply itself | Whole-house diagnosis |
| Upstairs only | House pressure too low to carry the height | Whole-house diagnosis |
| Came on suddenly after plumbing work | Debris knocked loose and lodged downstream | Flush every fixture |
| Brand new faucet, never had good flow | Flow restrictor or install debris | See the new faucet section |
If the weak flow is everywhere rather than at one tap, stop here. That is a different problem with different causes and different costs, set out in low water pressure in the home.
1. The Aerator, Which Is Most of Them
The aerator is the screw-on screen at the faucet tip. It mixes air into the stream, and its fine mesh catches every particle of sediment and scale that comes down the line. On Houston water it clogs faster than almost anywhere else.
- Close the drain. Aerators come apart into three or four small pieces.
- Unscrew it counter-clockwise. Wrap the tip in cloth before using pliers so the finish is not marked.
- Photograph the parts before separating them. The screen, restrictor and washer go back in one specific order and direction.
- Soak in white vinegar for four hours. Brush the mesh with an old toothbrush, then rinse.
- Run the faucet before reassembly to flush anything loose inside the spout.
- Hand-tighten only. Overtightening crushes the washer and causes a drip.
If you are doing this more than twice a year, the water is the problem rather than the faucet. The mineral mechanism and the permanent fix are in hard water solutions.
2. A Brand New Faucet With Weak Flow
This is a different problem from a faucet that gradually weakened, and it catches a lot of people out right after an install.
The flow restrictor
New faucets ship with a flow restrictor in the aerator. EPA WaterSense labeled bathroom faucets cap at 1.5 gallons per minute against a federal maximum of 2.2, so a new faucet can legitimately deliver about a third less than the twenty year old one it replaced. Nothing is broken.
Install debris
Cutting into supply lines knocks scale and solder fragments loose, and they travel straight to the new aerator and stop there. Remove and flush it, then run the faucet with the aerator off for thirty seconds before putting it back.
Supply valves not fully opened
Angle stops get closed for the install and reopened by feel afterward. Half a turn short is easy to miss and looks exactly like a defective faucet. Open both fully, then back off a quarter turn.
The one that is actually a defect
Some pull-down kitchen faucets ship with a protective film or plug inside the spray head that is meant to be removed. If a brand new kitchen faucet has almost no flow in spray mode but normal flow in stream mode, unscrew the spray head and look inside before calling anyone.
3. Kitchen Faucets Have Their Own Failures
Kitchen faucets are more complicated than bathroom ones, and two parts fail that a bathroom faucet does not have.
The diverter valve
On a pull-down or side-sprayer faucet, a diverter routes water between the spout and the spray head. When it fails or fills with scale, you get weak flow in one mode and normal flow in the other, or weak flow in both. This is the most misdiagnosed kitchen faucet problem, because people clean the aerator repeatedly and the aerator was never the issue.
The test takes ten seconds: if stream and spray behave differently from each other, it is the diverter, not the aerator.
The spray head itself
Pull-down heads have their own screen, separate from the aerator. It clogs the same way and gets cleaned the same way, and plenty of people never realize it is there.
Longer hose runs
A pull-down faucet has several feet of flexible hose under the sink. Kinks from the weight sliding or from items stored against it restrict flow, and they are invisible until you clear the cabinet and look.
4. The Cartridge and the Angle Stops
Angle stops, check these before the cartridge
The angle stops are the small valves on the wall under the sink, one hot and one cold. They get bumped by things stored in the cabinet, and older multi-turn stops seize partly open. Turn each fully counter-clockwise and see whether flow improves.
If a stop will not turn, stop forcing it. A seized angle stop that snaps becomes an emergency in about two seconds.
The cartridge
If the aerator is clean and the stops are fully open, scale has reached the cartridge inside the faucet body. Removing it is the same procedure as fixing a handle leak, which is set out step by step in a faucet leaking from the handle.
On a two-handle faucet, work out which side first. Weak on hot only means the hot stem or the hot stop. Weak on both means something common to both, which is usually the spout or the aerator rather than either stem.
When It Is Not the Faucet
- Flow is weak at several fixtures but not all. That usually means a branch line, often galvanized pipe corroded closed.
- It got worse over years rather than weeks. Gradual decline across the house is pipe diameter closing up, not a clog.
- Rust-colored water or visible flakes. That is pipe material, and cleaning an aerator will not stop it coming.
- An angle stop will not close. Nothing else can be worked on safely until that is replaced.
- You have cleaned the aerator three times this year. The aerator is a symptom.
The same causes appear at the shower, where the parts are less accessible. That version is in shower head low pressure. And if the faucet turns out to need work rather than cleaning, faucet repair and installation covers what that involves in Houston.
Frequently Asked Questions
Why does one faucet have low water pressure when the rest of the house is fine?
Because the restriction is at that fixture rather than in the supply. In order of likelihood: a clogged aerator at the tip, a partially closed angle stop under the sink, scale inside the faucet cartridge, or a kinked supply line. All four are localized, and none of them indicate a problem with the house plumbing. Whole-house low pressure is a different diagnosis entirely.
Why does my kitchen faucet have low water pressure?
Kitchen faucets have two parts bathroom faucets do not. The diverter valve routes water between the spout and the spray head and fails with scale, which produces weak flow in one mode and normal flow in the other. Pull-down spray heads also have their own screen separate from the aerator. If stream and spray behave differently from each other, it is the diverter, not the aerator.
Why does my new faucet have low water pressure?
Usually one of three things, and none is a defect. New faucets ship with a flow restrictor, and a WaterSense labeled bathroom faucet caps at 1.5 gallons per minute against a federal maximum of 2.2, so it can legitimately deliver a third less than the old one. Cutting into supply lines also knocks debris loose that lodges in the new aerator. And angle stops closed for the install often get reopened by feel and left half a turn short.
How do I fix low water pressure in one faucet?
Start with the aerator: unscrew it, soak the parts in white vinegar for four hours, brush the mesh and rinse. If that does not help, open both angle stops under the sink fully. If flow is still weak, scale has reached the cartridge inside the faucet body and it needs removing and replacing. Check the supply lines for kinks while you are under there.
Why is water pressure low in my bathroom sink only?
Same causes as any single fixture, with one addition: bathroom faucets have a lower federal flow limit than kitchen faucets, so a bathroom sink will legitimately feel weaker than the kitchen tap even when both are working correctly. If it has always been that way, that is probably why. If it changed, start with the aerator.
What is an angle stop and why does it affect pressure?
The angle stops are the small shutoff valves on the wall under the sink, one for hot and one for cold. Partly closed, they restrict flow to that fixture while everything else in the house stays normal. They get bumped by items stored in the cabinet, and older multi-turn stops seize part-way open. Turn each fully counter-clockwise, then back off a quarter turn. If one will not turn, do not force it.
Why is only the hot water pressure low at one faucet?
The hot angle stop under the sink is the first thing to check, because a partly closed hot stop produces exactly this. If the stop is fully open, the next candidate is sediment in the water heater or a failing dip tube, which restricts hot supply across the house but shows up worst at the fixture farthest from the tank.
Does hard water cause low faucet pressure in Houston?
Yes, and it is the single most common driver here. Dissolved calcium and magnesium crystallize on aerator screens, inside cartridges and on spray head nozzles. Houston city water runs about 7 to 8 grains per gallon and suburban MUD well water often tests 11 to 17 or higher, so fixtures clog on a schedule rather than at random. Cleaning the aerator more than twice a year is the signal that the water, not the faucet, is the problem.
Cleaned the aerator and it is still weak?
That usually means the cartridge, an angle stop, or the supply line. We diagnose it in one visit and tell you which. Free estimates across Houston.
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