You turn on the kitchen tap on a January morning and get a cough of air, then nothing. In Ottawa that usually means one of two things: a pipe inside your house has frozen, or the water service pipe under your lawn has. They look the same from the tap, but the fix, and who pays for it, is completely different.
This guide covers both. It explains where pipes freeze in Ottawa homes, what to do before the cold sets in, how to thaw an indoor pipe without starting a fire or a flood, and when the right call is 3-1-1 rather than a plumber.
Why Ottawa pipes freeze
Water freezes inside a pipe when the pipe sits somewhere colder than zero for long enough. In Ottawa, that happens in two places.
Inside the house, the usual suspects are pipes that run along an outside wall, through an unheated garage or crawl space, under a kitchen sink on an exterior wall, or near a leaky rim joist in the basement. A small draft blowing on a copper pipe at minus 25 can freeze it overnight, even in a warm house.
Outside the house, the risk is the water service pipe, the underground line that connects your plumbing to the City's watermain. As the City explains, when frost goes deep the ground around that line becomes a frozen block, and some service pipes run right through it. This tends to show up later in the winter, after weeks of hard cold, and often in the same streets year after year.
Inside or outside? How to tell
Before you do anything, work out which kind of freeze you have. Try every cold tap in the house, starting with the lowest one, usually the laundry tub or a basement sink.
| What you see | What it usually means |
|---|---|
| One tap or one bathroom has no water, others are fine | A pipe inside your house has frozen, close to that fixture |
| No cold water anywhere in the house | Possibly the water service pipe; it can also be a freeze where the main enters the basement |
| Water slows to a trickle over a few days, everywhere | Often a service pipe slowly freezing; report it early |
| Water is fine but you hear dripping or see a stain | A pipe may have frozen and split; shut the water off and call a plumber |
If no tap in the house works, the City of Ottawa asks you to call 3-1-1 to report a frozen service pipe. Its crews deal with frozen service lines every winter. If only part of the house is affected, the pipe is almost certainly yours, and that is plumber territory.
Before the cold: prevention that works
Most frozen pipes are preventable, and nearly all of these steps cost little or nothing.
- Shut off and drain your outside taps in the fall. Close the indoor shut-off valve for each hose bib, then open the outside tap to drain it and leave it open. A frost-free hose bib still needs the hose disconnected.
- Find your main shut-off valve now. It is usually where the water line comes through the basement floor or wall, near the meter. If a pipe bursts you want to find it in seconds, not minutes. Make sure it turns.
- Seal the drafts. Spray foam or caulk around the spot where pipes, wires and vents pass through the outside wall. The rim joist above the foundation is a common cold spot.
- Insulate exposed pipes in crawl spaces, garages and along outside walls with foam pipe sleeves. Where a pipe has frozen before, consider a thermostat-controlled heat cable rated for pipes, installed exactly as its instructions say.
- Open the cabinet doors under sinks on outside walls during cold snaps, so warm room air reaches the pipes.
- Keep the heat on when you travel. A setting that feels cool, rather than the lowest the thermostat allows, protects pipes on outside walls. Ask someone to check the house if you are away for more than a couple of days in deep cold.
If the City sends you a "run water" letter
Each winter, when the frost gets deep enough, the City of Ottawa sends a run-water advisory to properties at risk, often ones where the service pipe has frozen before. The City has said up to about 2,000 homes and businesses may get one in a season.
If you get that letter, follow it. The City's instruction is to run a continuous, steady stream of cold water, at least as wide as a drinking straw, until the frost is out of the ground, which it puts at the end of April. Moving water is much harder to freeze. The City has said that for these notified properties, the water bill is calculated from previous consumption patterns rather than charging for every litre you let run.
How to thaw an indoor pipe safely
If you have worked out that the frozen section is inside your house and you can reach it, you can often thaw it yourself. Go slowly. A pipe that thaws too fast, or too hot, can split or start a fire.
- Open the tap the pipe feeds, so melting water has somewhere to go and you will know the moment it flows again. The City suggests opening the cold tap nearest the frozen section.
- Find the frozen spot. Follow the pipe back from the tap. Frost on the pipe, a bulge, or the coldest point along an outside wall is usually it.
- Warm it gently. A hair dryer moved back and forth along the pipe, starting at the tap end and working back, is the safest tool most people own. A space heater placed safely nearby, or towels soaked in hot water wrapped around the pipe, also work.
- Never use an open flame. No propane torch, no lighter, no candle. A flame can set wood framing or insulation alight inside the wall, and it can overheat soldered joints.
- Check for leaks as the water starts to flow. Frozen water expands, and the split is often a short distance from the ice. Watch the pipe for a few minutes once water runs.
- Keep the tap dripping for the rest of the cold spell and fix the draft or insulation that caused it.
If you cannot reach the frozen section, if it is inside a finished wall or ceiling, or if a few hours of gentle warming do nothing, stop and call a plumber. Plumbers have tools that thaw pipes inside walls without opening them up.
When a frozen pipe bursts
A burst pipe often does not leak while it is still frozen. The water arrives when it thaws. If you see water, hear spraying, or notice a ceiling stain spreading:
- Shut the main water valve right away.
- Turn off electricity to any area where water is near outlets, fixtures or the panel, if you can do it safely. If you cannot, stay out of that area.
- Open a tap at the lowest point in the house to drain the pressure.
- Take photos for your insurer before you start mopping.
- Call a plumber to find and repair the split, and to check other pipes on the same wall.
That is exactly the kind of call our emergency plumbing team handles. If the water has reached the basement floor, it is also worth checking that your sump pump is working; see our page on sump pump installation if yours is old or struggling.
Quick answers
At what temperature do pipes freeze?
There is no single number. It depends on how exposed the pipe is and for how long. A well-insulated pipe in a heated wall can ride out a deep cold snap, while a pipe beside a draft can freeze on a night that is only a little below minus 10. Pipes that froze once tend to freeze again until the cause is fixed.
Should I leave a tap dripping every night?
If a pipe in your house has frozen before, a small steady flow from the tap it feeds, during the coldest nights, is cheap insurance. If the City has sent you a run-water letter, follow its instructions instead, which call for a steady stream until the frost is out of the ground.
Who pays to fix a frozen water service pipe?
Report it to 3-1-1 first. The City handles frozen service pipes and will tell you what applies to your property. A frozen or burst pipe inside your house is a private plumbing repair.
Can I use a heat gun or torch?
A torch, no, never. A heat gun can get hot enough to damage plastic pipe and soldered joints, so a hair dryer on a normal setting is the safer choice for most people.
The Ottawa Plumber deals with frozen and burst pipes all winter. If water is coming through a ceiling or you have no water and 3-1-1 has confirmed the problem is inside your house, call and describe what the water is doing.