How small a leak is worth calling about?

Any leak on a pressurized line, no matter how small. A drip that has run for months has often already done more damage to the surrounding material than the repair itself will cost.

Should I shut off the water main?

If water is flowing where you can't control it, yes — shutting off the main is the single most effective thing a homeowner can do. For a contained slow drip, shutting off the valve for that one fixture is usually enough.

Will my insurance cover it?

Coverage varies widely by policy and by cause, and gradual leaks are often treated differently from sudden ones. Document what you find with dated photos and speak to your insurer directly.

Pipes

Leaking Pipe: How to Read the Signs and What to Do Next

Water escaping from a supply or drain pipe — sometimes visible, often hidden inside a wall, ceiling, or floor.

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

If this is an emergency

Uncontrolled water, sewage entering the home, a suspected gas leak, or water near electrical equipment all need immediate action. Shut off the water at the main if it is safe to reach, keep everyone away from hazards, and contact your local emergency services, your utility provider, or a licensed professional as appropriate.

What's happening?

Your home has two separate pipe systems: pressurized supply lines that bring water in, and drain lines that carry it away by gravity. A supply leak pushes water out continuously, whether or not anyone is using a fixture. A drain leak only releases water while something upstream is running, which is why it can go unnoticed far longer.

Most of the cost and damage from a leak doesn't come from the water you can see. It comes from the material it soaks into — framing, insulation, subfloor, drywall, cabinetry — and from how long it stays wet. That's why speed matters more than size.

Common signs

Symptoms homeowners notice

A stain, bubble, or sag on a ceiling or wall, sometimes with a ring pattern
A musty smell in one room, a closet, or a cabinet
The sound of running water when every fixture is off
A water bill that rises with no change in household use
Warm or persistently damp spots on a floor
Paint or wallpaper lifting, or baseboards swelling

Possible causes

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

A failed joint or connection: Fittings, solder joints, and threaded connections are the most common leak points, especially after age or movement.
Corrosion: Older galvanized steel and some copper systems corrode from the inside until a pinhole opens.
Physical damage: A nail or screw driven into a concealed pipe, or a pipe knocked during other work, can leak slowly for a long time.
Freeze damage: A pipe that froze — even in a past winter — may have been split and only leak once pressure conditions change.
High water pressure: Pressure above the normal residential range stresses joints, valves, and appliance connections throughout the home.
A failed appliance connector or valve: Supply lines to toilets, dishwashers, ice makers, and washing machines are frequent culprits and are often mistaken for pipe leaks.

How urgent is it?

High — address promptly

Even a slow leak causes progressive damage and can support mold growth. Address it promptly. A fast, uncontrolled leak is an emergency.

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.

Find out whether the water is running constantly or only when a fixture is in use — this separates supply leaks from drain leaks.
Look under every sink and behind the toilet with a flashlight and a dry paper towel; a towel finds moisture your eyes miss.
Check the washing machine and dishwasher hoses and the water heater pan.
Locate your main water shut-off valve now, before you need it, and make sure you know how to turn it.
If your meter has a leak indicator, turn off all water use and watch whether it still moves.
Photograph the stain or wet area with the date — useful for both the plumber and any insurance claim.

What not to do

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

Avoid these

Don't hide the evidence. Painting over a stain or closing up a wet cabinet only delays the diagnosis while the damage continues.
Don't treat tape, epoxy putty, or a clamp as a repair. At best they buy time until a proper repair; they are not a fix on a pressurized line.
Don't open a ceiling that is sagging and holding water — it can release a large volume at once.
Don't touch anything electrical near standing water, and don't use an outlet or switch in a wet area.
Don't cut into a wall to hunt for the leak yourself; concealed pipes, wiring, and gas lines run in the same cavities.

Can I fix this myself?

Safe to check

Observation and low-risk checks most homeowners can make.

Looking for stains, drips, and damp spots
Checking under-sink and appliance connections with a dry towel
Locating and testing your main shut-off valve
Reading the water meter to confirm continuous flow

Proceed with caution

Minor actions where instructions must be followed carefully.

Shutting off water to a single fixture at its own valve
Placing a container and towels to catch a drip while you wait for service

Call a professional

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

Any repair to pressurized supply piping
Leak detection inside walls, ceilings, floors, or slabs
Repiping or replacing a run of pipe
Any leak near electrical equipment

When to call a licensed plumber

Clear signals it's time for professional help

You can see water but can't find where it's coming from
The leak is inside a wall, ceiling, floor, or slab
Water is near electrical panels, outlets, or fixtures
Any leak on a pressurized supply line, however small
There's staining or a musty smell suggesting the leak has been there a while

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

1How will you locate the leak, and will that require opening walls or floors?
2Is this a repair to one spot, or a sign the piping is near the end of its life?
3Who handles the drying and the drywall or finish repair — you, or a separate contractor?
4What is my water pressure, and is it within the normal range?
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

Accessibility: A pipe in an open basement is far cheaper to reach than one under a slab or inside a finished ceiling.
Leak detection: Concealed leaks may need acoustic or thermal equipment, usually billed separately.
Pipe material and age: Repairing failing galvanized or aging copper can lead to a recommendation to replace a section or a run.
Restoration: Drying, drywall, paint, tile, and flooring are often a bigger share of the total than the plumbing itself.
Extent of water damage: How long the leak ran drives whether remediation is needed.
Emergency timing: After-hours response carries premium labor rates.

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

Common questions

How small a leak is worth calling about?: Any leak on a pressurized line, no matter how small. A drip that has run for months has often already done more damage to the surrounding material than the repair itself will cost.
Should I shut off the water main?: If water is flowing where you can't control it, yes — shutting off the main is the single most effective thing a homeowner can do. For a contained slow drip, shutting off the valve for that one fixture is usually enough.
Will my insurance cover it?: Coverage varies widely by policy and by cause, and gradual leaks are often treated differently from sudden ones. Document what you find with dated photos and speak to your insurer directly.

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