Is there an active leak at this fixture or water near electrical outlets?

Which side is weak at this fixture?

Unscrew the aerator (or showerhead) and run the faucet. Does flow return to normal with it off?

If you can't unscrew it, soak in vinegar for an hour first.

Look at the angle stop under the fixture. Is the handle fully open, and does the valve look old, corroded, or partly turned?

How old is the faucet cartridge or valve, and has the fixture been serviced recently?

plumbing troubleshooting

Fix water pressure at a fixture

Common symptoms: low pressure at sink; weak faucet flow; low pressure one fixture; slow tap; weak shower one fixture

Stop and call a pro if:

shut off water at the angle stop before disassembling

Step-by-step diagnostic flow

Step 1
Is there an active leak at this fixture or water near electrical outlets?
Step 2
Which side is weak at this fixture?
Step 3
Unscrew the aerator (or showerhead) and run the faucet. Does flow return to normal with it off?
If you can't unscrew it, soak in vinegar for an hour first.
Step 4
Look at the angle stop under the fixture. Is the handle fully open, and does the valve look old, corroded, or partly turned?
Step 5
How old is the faucet cartridge or valve, and has the fixture been serviced recently?

Possible outcomes

Stop and address the hazard first

high confidence

Active leak or electrical hazard must be resolved before troubleshooting.

Safe next steps

Shut off the angle stop or main water
Clean up standing water before further work

Active leak or electrical hazard

Likely a hot-side restriction at the water heater or supply

medium confidence

Hot-only weakness usually means scale buildup in the water heater, a partially closed heater shutoff, or a clogged hot supply line.

Safe next steps

Verify the hot-side shutoff on the water heater is fully open
Note whether other hot taps in the house are also weak

What to document for a pro

Water heater age and type
Whether multiple hot fixtures are affected

Clogged aerator or showerhead — DIY clean or replace

high confidence

Flow returned to normal with the aerator removed, confirming it as the restriction.

Safe next steps

Soak the aerator in white vinegar for 1-2 hours
Brush out debris and reinstall, or replace with a matching aerator
Run the faucet briefly before reinstalling to flush the line

Angle stop not fully open

high confidence

A partially closed angle stop will throttle flow to the fixture.

Safe next steps

Open the angle stop fully (counterclockwise on multi-turn, in-line on quarter-turn)
If it will not turn freely, plan to replace it — see the Replace angle stop project

Angle stop should be replaced

high confidence

Corrosion or leaking at the angle stop will only worsen and is restricting flow.

Safe next steps

Open the 'Replace angle stop' project workflow
Shut water at the main before disassembly if the angle stop will not isolate

What to document for a pro

Photo of the angle stop and supply stub
Wall stub material if visible

Likely worn faucet cartridge

medium confidence

Old single-fixture cartridges can clog with sediment or fail internally, restricting flow.

Safe next steps

Identify the faucet brand and model (often on the underside or in the manual)
Buy the matching cartridge and replace per the manufacturer's instructions

What to document for a pro

Faucet brand and model
Photo of the faucet handle/spout

Further diagnosis recommended

low confidence

Non-invasive checks did not isolate the restriction.

Safe next steps

Photograph the supply, angle stop, and faucet body
Note whether the problem is constant or intermittent

What to document for a pro

Faucet brand/model
Photos of supply line and angle stop
Whether other fixtures share the same branch

Diagnostic guidance only. If unsure, stop and call a licensed professional — gas, electrical, and refrigerant work is hazardous to untrained users.

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