Emergency Plumbing: What to Do Before the Plumber Arrives

A plumbing emergency is stressful, disorienting, and often happens at the worst possible time. But the actions you take in the first few minutes — before the plumber arrives — can make a significant difference in the amount of damage your home sustains.

This guide walks through what to do in the most common plumbing emergencies. The most important first step in almost every situation is the same: know how to shut off the water. Read this guide before an emergency happens so you're ready.

The First Step in Almost Every Emergency: Shut Off the Water

Whether it's a burst pipe, a leaking water heater, or a toilet overflow, the first action is almost always to stop the flow of water. Water that keeps flowing means damage that keeps accumulating — every minute matters.

Know where your main water shutoff valve is before an emergency. In most Ontario homes, it's in the basement within 1–2 feet of where the water main enters through the foundation wall — typically toward the front of the house. See our dedicated guide on finding and using your main shutoff valve for a full explanation.

• Gate valve (round wheel): Turn clockwise to close. May take multiple full turns. Note: old gate valves often fail to fully close — if it doesn't stop water, use the fixture shutoff instead.
• Ball valve (lever handle): Quarter-turn clockwise (perpendicular to pipe) to close. More reliable than gate valves.

After shutting off the main water, open a downstream tap (a bathroom faucet or hose bib) to relieve pressure in the system and drain remaining water from the pipes.

Burst or Leaking Pipe

If the leak is from a supply line under a sink or behind a toilet, use the individual fixture shutoff valve (under the sink, behind the toilet near the floor) rather than shutting off the whole house. This allows you to use other water-using fixtures while waiting for the plumber.

Toilet Overflow

An overflowing toilet is one of the most common household plumbing emergencies. Here's what to do:

1. Remove the tank lid and locate the flapper — the rubber disc at the bottom of the tank. Press it down firmly to prevent more water from entering the bowl while you work.
2. Turn off the toilet's individual shutoff valve — it's behind and below the toilet, near the floor. Turn it clockwise to close.
3. If the toilet bowl is filled with water that won't drain, do not flush again. Flushing with a full bowl will cause it to overflow further.
4. Try a plunger — use a flange plunger (designed for toilets, with a rubber lip that fits into the drain). Apply firm, steady plunging — not rapid jabbing. If the toilet drains, flush once cautiously to confirm.
5. If plunging doesn't clear it, call a plumber. Repeated overflow often indicates a deeper blockage in the drain stack, not just the toilet itself.

Sewer Backup

A sewer backup — sewage coming up through floor drains, toilet bases, or shower drains — is a health hazard and requires immediate action.

1. Stop using all plumbing immediately. Every time water runs down any drain, it pushes more sewage backward into your home.
2. Do not flush toilets until the blockage is cleared.
3. Keep people and pets away from the sewage. Raw sewage contains harmful bacteria and pathogens.
4. Do not use fans to dry the area — this aerosolizes pathogens. Open windows for ventilation only.
5. Document the damage with photos before any cleanup.
6. Call a licensed plumber to clear the main sewer line. See our guide on drain cleaning services.
7. Contact your insurer. Sewer backup coverage is an optional endorsement on most Ontario home policies — check your policy.

For Toronto and Mississauga homeowners: if the backup is coming from the municipal sewer (not just your own line), you may also need to contact the city. A licensed plumber can help determine the source.

No Water at All

If water has suddenly stopped flowing to your entire home:

1. Check that the main shutoff valve is fully open. It's possible someone accidentally moved it, or an old gate valve has stuck in a partially closed position.
2. Check with neighbours. If multiple homes on your street have lost water, it's a municipal supply interruption. Check your city's service outage alerts or call 311.
3. Check your water meter. If the meter is registering flow when nothing is running, you have a hidden leak — possibly a burst pipe elsewhere in the house or underground.
4. Check the water heater shutoff. In some homes, the cold water supply to the water heater has a separate shutoff that can affect apparent hot-only loss.
5. If the issue is isolated to your home and not municipal, call a licensed plumber to diagnose the cause.

Leaking Water Heater

A leaking water heater needs to be addressed quickly to prevent basement flooding and water damage. See our detailed guide on water heater replacement. For immediate action:

1. Turn off the cold water supply to the water heater — there's a shutoff valve on the cold water inlet pipe at the top of the unit. Turn it clockwise to close.
2. For gas water heaters: Turn the gas valve to the "Pilot" position (or off) to prevent the burner from firing with no water in the tank.
3. For electric water heaters: Turn off the circuit breaker for the water heater to prevent the element from running dry.
4. Connect a garden hose to the drain valve at the base of the tank and route it to a floor drain to drain the tank if needed.
5. Call a licensed plumber. A leaking tank cannot be reliably repaired — replacement is required.

Suspected Frozen Pipe

If a tap produces no water during Ontario's winter months, a frozen pipe is the likely culprit. See our full frozen pipe emergency guide. Key immediate steps:

1. Shut off the main water supply before attempting to thaw — a frozen pipe may already have a crack that hasn't yet leaked. Shutting off the water prevents flooding when it thaws.
2. Never use an open flame to thaw a pipe. A hair dryer on the lowest setting, warm towels, or a heating pad are safe methods.
3. If you cannot locate or access the frozen section, or if you suspect the pipe may already be cracked, call a licensed plumber before attempting to thaw.

What to Tell the Plumber When You Call

Providing clear information when you call helps the plumber respond quickly and bring the right materials:

• Your complete address, including unit/apartment number if applicable
• Brief description of the emergency (burst pipe, backup, no water, etc.)
• Whether you have already shut off the main water supply
• The location in the home where the problem is occurring
• Any access issues (locked gate, difficult parking, pets that need to be secured)
• If you can send photos to the plumber's number ahead of arrival, this helps significantly

Prevention: Know Your System Before an Emergency

The best time to prepare for a plumbing emergency is before one happens. Take these steps now:

• Locate and test your main shutoff valve. Turn it to confirm it closes fully.
• Note the location of individual fixture shutoffs under sinks and behind each toilet.
• Know your water heater location and its gas and water shutoffs.
• Test your sump pump annually — pour water into the pit to trigger the float. See our sump pump maintenance guide.
• Insulate pipes in unheated spaces before winter — particularly in garages, crawl spaces, and exterior walls. See our plumbing winterization guide.
• Consider a water leak detector — inexpensive wireless sensors under sinks and near the water heater alert you to leaks before they become emergencies.
• Have a licensed plumber's number saved — finding a reputable plumber in the middle of an emergency adds stress and time.

Mechora Group's licensed plumbers serve Toronto, Mississauga, Brampton, Vaughan, and across the GTA. Save our number: (249) 733-7907. Our emergency plumbing service team responds promptly to minimize damage to your home.