How often should you exercise the water shut-off valves?

Short answer

Exercise the water shut-off valves every 6 to 12 months. That means finding every valve that can stop water in the house, the main one where the supply comes in and the small ones under sinks and behind toilets, and turning each one closed and open again. A valve that hasn't moved in years seizes, and the moment you discover that is usually the moment a pipe is spraying. The round takes 10 to 15 minutes and costs nothing.

Why it matters

Every burst pipe, failed hose and overflowing toilet comes down to one question: how fast can you stop the water? A supply line under pressure puts out gallons a minute, and a few minutes is the difference between a wet floor and a ruined ceiling below it. The shut-off valve is the answer, if it turns.

Valves seize because they sit still. Minerals in the water settle around the stem and the seat, and the packing around the stem dries out. The handle corrodes to the body. A gate valve, the kind with a round wheel handle, is the worst offender: its gate drops into a slot and binds there, and forcing it can snap the stem off. Working each valve once or twice a year keeps everything moving, and shows you which ones have already failed while there's time to replace them calmly.

When to do it more often

Twice a year is plenty for valves that move freely. The reasons to do it sooner are about the valves themselves rather than the calendar:

A valve that was stiff last time. Work it again in a month or so to see whether it loosened, and plan to replace it if it didn't.
A new home, or one you've just moved into. Find and work every valve in the first week, because you'll need the main one before you need anything else.
Before a long trip. Many people close the main valve when they leave for weeks, and that's a good time to be sure it turns.

What you need

An adjustable wrench, for a handle that's stiff or a valve with no handle left
A flashlight, since the main valve is often in a dim corner of a basement, crawl space or utility closet
A rag, to dry the valve and spot any drip afterward

Steps at a glance

Find the main shut-off where the water line enters the house, and the valve at the meter if you have access to it.
Close the main valve fully and open it again, then run a tap to confirm water flows.
Go through the house: under each sink, behind each toilet, at the washing machine, the water heater and the refrigerator's ice line.
Close and reopen each valve, counting the turns on a round handle so you know it went all the way.
Dry each valve with the rag and look for a drip at the stem a minute later.
Note any valve that wouldn't turn, dripped after turning, or looks corroded.

You're done when every valve has closed and reopened, water runs at the taps, and no stem is dripping.

Signs it's overdue

A valve that won't turn by hand.
A valve that drips from the stem after you've turned it, because the packing dried out while it sat.
Green or white corrosion on the stem or where the handle meets the body.

DIY or pro

Exercising valves is easy, and it's the kind of job that fits a Saturday morning with a cup of coffee. The one rule is not to force anything. A valve that resists a firm hand is already failing, and a stem that snaps off a main valve leaves you with no way to shut off the house and a plumber on an emergency rate.

Replacing a stuck main shut-off is a plumber's job, since the water has to be stopped at the street first, and it costs $150 to $400. The small valves under sinks are a moderate job for a handy owner, and a plumber will often replace a few at once while they're there. If the main valve is a gate valve, consider replacing it with a quarter-turn ball valve even if it still works, because a ball valve is far less likely to seize.

Safety

Pressure: the main line is under full street pressure. Open a closed valve slowly to let the pressure build gradually, and if a valve starts to leak from the stem when you turn it, don't keep working it. Snug the packing nut gently with the wrench, and if the drip continues, leave the valve open and have it replaced.

FAQ

Where is the main water shut-off valve?

Where the supply line enters the house, usually in a basement, crawl space, garage or utility closet on the side facing the street. In a warm climate it may be outside near the foundation or at the meter.

What if the shut-off valve won't turn?

Don't force it. Work it gently back and forth with the wrench, and if it doesn't free up, have it replaced. A main valve that won't turn is an emergency waiting to happen.

Should I close the main water valve when I go on vacation?

Yes, if it turns easily. A closed main valve means a failed hose or fitting can't flood the house while nobody's home.

Why does the valve drip after I turn it?

The packing around the stem dried out while the valve sat. A gentle quarter turn on the packing nut often stops it. If not, the valve needs replacing.