Only one faucet is weak. Where do I start?

The aerator. Sediment and scale in that small screen is the single most common cause, and checking it is a low-risk homeowner task.

Pressure dropped across the whole house overnight. Is that serious?

It deserves prompt attention. A sudden whole-house drop can mean a valve issue, a failed pressure-reducing valve, a supply-side problem, or a leak — and a leak is the reason not to wait.

Why is only my hot water weak?

That points at the water heater or its supply — a partly closed heater shut-off, sediment inside the tank, or a restriction on the hot side. It's worth having the heater assessed.

Water Supply

Low Water Pressure: Narrowing Down the Cause

Water flows weakly. Whether it's one fixture or the whole house tells you almost everything about where to look.

A homeowner guide — what may be happening, and what to do next.

What's happening?

Pressure is the force pushing water through your pipes; flow is how much actually arrives. Homeowners notice flow, and it can drop either because pressure fell or because something is restricting the path.

The first question is scope. One fixture means a local restriction — an aerator, a cartridge, a supply valve, a flexible line. Every fixture means something shared: the main shut-off, a pressure-reducing valve, a whole-house filter, corroded supply piping, a leak, or the municipal supply itself. A sudden whole-house change deserves more attention than one that developed slowly over years.

Common signs

Symptoms homeowners notice

A weak stream or a shower that lacks force
Fixtures that take a long time to fill a sink or tub
Pressure that drops when another fixture or appliance runs
Hot water weaker than cold, or the reverse
Sputtering or air in the line
A sudden change that happened in one day

Possible causes

From simple to more serious — not a diagnosis of your specific situation

A clogged aerator or showerhead: Sediment and scale collect in the screen. The most common single-fixture cause and the easiest to check.
A partially closed valve: The main shut-off or a fixture valve not fully open after previous work.
A failed pressure-reducing valve: Where fitted, a failing PRV can drop pressure across the entire home.
A clogged whole-house filter: An overdue filter cartridge restricts flow everywhere.
Corroded or scaled supply piping: Older galvanized pipe narrows internally over decades; usually a gradual decline.
A leak in the supply line: Water escaping before it reaches your fixtures, sometimes underground with no visible sign.
A municipal or well system issue: Utility work, a neighborhood main break, or a well pump / pressure tank problem.
A failing water heater or its supply: If only hot water is weak, look at the heater, its shut-off, and sediment inside it.

How urgent is it?

Medium — schedule professional service

Usually not urgent on its own, but a sudden whole-house drop can indicate a leak or a supply problem and should be investigated promptly.

Low
Medium
High
Emergency

What you can safely check

Simple observations and low-risk checks. None of these require tools you don't have or work you aren't qualified for.

Test every fixture, hot and cold separately, and note which are affected — this single step narrows the cause dramatically.
Unscrew and inspect a faucet aerator for grit and scale.
Confirm the main shut-off valve is fully open.
Check whether a whole-house filter is overdue for a cartridge change.
Ask a neighbor whether they've noticed a change — that separates your plumbing from the supply.
Look for damp ground, unusually green patches, or a moving water meter with everything off, which suggest a supply leak.

What not to do

These are the actions that turn a manageable problem into an expensive or dangerous one.

Avoid these

Don't adjust or disassemble a pressure-reducing valve, a well pressure tank, or a backflow preventer yourself. These are calibrated devices and, in the case of backflow prevention, often regulated.
Don't crank a pressure setting up to compensate. Excess pressure causes leaks, damages appliances, and can void warranties.
Don't force a stiff old shut-off valve; they snap.
Don't ignore a sudden whole-house drop — it can be the first sign of a hidden leak or a burst.
Don't remove or bypass a backflow prevention device.

Can I fix this myself?

Safe to check

Observation and low-risk checks most homeowners can make.

Testing each fixture, hot and cold, to map the problem
Inspecting and rinsing a faucet aerator or showerhead screen
Confirming shut-off valves are fully open
Checking with neighbors and reading the water meter

Proceed with caution

Minor actions where instructions must be followed carefully.

Replacing a whole-house filter cartridge following the manufacturer's instructions
Replacing a showerhead

Call a professional

Regulated, hazardous, or specialized work. Don't attempt it.

Pressure-reducing valve diagnosis or replacement
Well pump and pressure tank work
Supply line leak detection and repair
Repiping corroded supply lines
Backflow prevention devices

When to call a licensed plumber

Clear signals it's time for professional help

Every fixture in the home is affected
The drop happened suddenly and neighbors are unaffected
You have older galvanized piping and pressure has declined for years
Only hot water is weak, or you suspect a water heater issue
You suspect a leak in the underground supply line

Not sure yet? Read our general guidance on when a plumber is needed.

Questions to ask your plumber

Worth covering before you authorize any work.

Before work starts

1What is my static pressure reading, and what should it be for this area?
2Do I have a pressure-reducing valve, and how is it performing?
3Is the piping material itself limiting flow, and what would improving it involve?
4Could this be caused by a leak, and how would you confirm that?
5Are you licensed to do this type of work in my area, and can I see your license number?
6Do you carry liability insurance and workers' compensation?
7Will you provide a written estimate before starting work?
8Is a diagnostic or trip fee charged, and is it applied to the repair if I go ahead?
9Does this work require a permit or an inspection?
10What warranty applies to the labor, and what warranty applies to the parts?

What could affect the cost?

We don't publish prices, because real quotes depend on your home, your area, and what's found on site. These are the variables that move the number.

Cost drivers

One fixture vs. the whole house: A cartridge or aerator is minor; repiping is a major project.
Diagnostics: Pressure testing and leak detection may be billed separately.
Valve replacement: Replacing a PRV or main shut-off is a defined job; access affects the price.
Pipe material and length: Replacing corroded supply lines depends on the run length and how much is concealed.
Underground work: Excavating a service line brings in permits, restoration, and sometimes utility coordination.

More detail on how plumbing work is priced: Plumbing costs — what to expect.

Common questions

Only one faucet is weak. Where do I start?: The aerator. Sediment and scale in that small screen is the single most common cause, and checking it is a low-risk homeowner task.
Pressure dropped across the whole house overnight. Is that serious?: It deserves prompt attention. A sudden whole-house drop can mean a valve issue, a failed pressure-reducing valve, a supply-side problem, or a leak — and a leak is the reason not to wait.
Why is only my hot water weak?: That points at the water heater or its supply — a partly closed heater shut-off, sediment inside the tank, or a restriction on the hot side. It's worth having the heater assessed.

This guide is general educational information, not a diagnosis of your specific situation. Plumbing codes, regulations, and licensing requirements vary by state and locality.