A burst pipe, leaking fixture, or running toilet that won't stop — every homeowner has 30 seconds to shut off water before significant damage starts. Knowing where the main water shutoff valve is, and how to operate it, is one of the most important things to learn about your home. This is a 5-minute education that can prevent thousands of dollars in flood damage.

This guide covers locating and operating the main shutoff plus fixture-level shutoffs.

Before you start

Three things to know:

1. Two levels of shutoff. Main shutoff: closes water to the entire house. Fixture shutoff: closes water to one specific fixture (toilet, sink, washing machine). For most leaks, fixture shutoff is sufficient and faster. For burst pipes or major leaks, main shutoff stops everything.

2. Find both NOW, not during emergency. Walk your house this weekend. Locate the main shutoff and at least know where each fixture's shutoff is. Test that valves turn (some get seized). Mark valve locations with a small label or photo. This 15-minute exercise pays back the first time something leaks.

3. Two valve types. Quarter-turn ball valve: one quarter turn (90°) to fully close. Lever handle perpendicular to pipe = closed. Most modern valves are this type. Gate valve (round handle): turn clockwise multiple times to close. Found in older homes.

What you'll need

Tools

Just your hands — but seized valves may need a wrench

Materials

Optional: shutoff valve label or marker (for future reference)

Locate the main shutoff today

Don't wait until water is spraying in your basement to find the main shutoff. Spend 15 minutes this weekend locating it. Test that it turns. Take a photo of its location.

The main shutoff is typically: in the basement near where the water line enters from outside, in a utility closet on a slab-foundation home, or near the water meter.

Step-by-step instructions

Find the main shutoff (now, not in emergency)

Walk your basement (or utility room) and find where the main water line enters the home. Usually a 3/4 to 1 inch pipe with a valve.

Common locations: front basement wall (where the line enters from the street), near the water heater, in a utility closet near a sump pit.

If you can't find it, ask your home inspector or a plumber on a service call — they identify it as part of every assessment.

Test that the main shutoff actually turns

Try turning the valve. Quarter-turn ball valves: should turn 90 degrees with hand pressure. Gate valves: should turn smoothly clockwise multiple times.

If the valve is seized (won't turn or only partially closes), have a plumber replace it. A non-functional shutoff is a major issue — replace before you need it.

Identify fixture shutoffs

Each toilet, sink, dishwasher, and washing machine should have its own shutoff valve nearby. Walk the house and note locations.

Toilet: small valve on the wall behind the toilet, near the floor.

Sink: under the sink, on the supply lines.

Washing machine: behind the machine on the wall (typically two valves, hot and cold).

Dishwasher: under the kitchen sink (the dishwasher's supply line connects to the sink's shutoff or has its own).

Emergency: shut off the closest fixture valve first

If a leak is at one fixture (running toilet, leaking faucet, washing machine hose burst), close that fixture's shutoff valve.

Quarter-turn ball valve: rotate 90 degrees so the lever is perpendicular to the pipe.

Gate valve: turn clockwise until firm. Don't over-tighten — you can damage the valve.

If fixture valve fails or leak is more widespread: main shutoff

Run to the main shutoff. Close it.

All water in the house stops within seconds. Burst pipes stop spraying; leaks stop flowing.

Open faucets to relieve pressure

After closing the main, open the lowest-level faucet (typically a basement laundry faucet or outdoor spigot) to drain residual water out of the system.

This relieves pressure on damaged components and reduces residual leaking.

Address the leak source

With water off, you can now investigate and fix or call a plumber.

Don't restore water until the leak is fixed or you have a plan to mitigate further damage.

After repair: turn water back on slowly

Open the main shutoff slowly to gradually re-pressurize the system. Watch for any new leaks.

Run water at multiple fixtures to clear air from the lines.

If any fixtures don't have water, check that their individual shutoff valves are open.

Common mistakes that cost you

Not knowing where shutoff is. Wastes critical minutes during emergency. Find and test today, not when water is spraying.
Seized valves. Non-functional shutoff is a major issue. Test annually; replace if seized.
Closing main when fixture valve would suffice. Slower, affects whole house. Use fixture-level shutoff for localized leaks.
Not opening faucets after main shutoff. Pressure remains in lines. Open low-point faucet to drain.
Restoring water without fixing leak. Water resumes flowing through damaged component. Fix first, then restore.

Frequently asked questions

What if the main shutoff is seized?

Call a plumber to replace it. A seized main shutoff is a major issue — you have no way to stop water in an emergency.

While the plumber's there, ask them to also verify all fixture shutoffs work. Many older homes have multiple seized valves.

Where's the city's curb stop valve?

Each home has a curb stop valve — the city's shutoff at the property line. It's underground, accessible only with a special tool (curb key) carried by city plumbers.

If your main shutoff fails, call the City of Ottawa (3-1-1) for emergency curb stop shutoff. They typically respond within hours.

Should I shut off water before vacation?

For trips longer than a few days, yes — closing the main shutoff prevents water damage from leaks while you're away.

Open faucets to drain pressure, then close all faucets. Re-open main and faucets sequentially when you return.

When to call us instead

Burst pipes and major leaks can cause extensive water damage if not stopped quickly. Knowing where to shut off water — and having functional valves — is the most important plumbing knowledge for any homeowner.

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Related Ottawa services

If your shutoff valves don't function or you have plumbing concerns, our renovation team coordinates plumber assessments as part of larger work. Book a free 60-minute consultation.