Surviving the Deep Freeze: How to Fix a Frozen Plumbing Stack in Winnipeg.
It’s -40 in January and suddenly your house begins to smell slightly of sewer gas. Your toilet makes a glug, glug noise when flushing and your sink is draining slowly. It’s possible that this is not the result of a clogged drain but a frozen plumbing stack.
This is a very common issue for those who live in cold places like Manitoba. Every year our plumbers are called to thaw plumbing stacks (also known as penetrating stacks) for customers in Winnipeg. Read on to find out how your plumbing stack works, why it freezes and what you can do about it.
What is a Plumbing Stack & How Does It Work?
A plumbing stack is the airway of your home's drainage system; A vertical pipe that usually runs from your basement, through your walls, and up out of your roof. While most people think plumbing is just about water, the stack is actually designed to move air. It serves two critical functions:
1. Releasing Dangerous Gases: As wastewater flows down into the city sewer or your septic tank, it produces gases like methane and hydrogen sulfide. Without a way to escape, these foul-smelling and potentially dangerous gases could be trapped in your pipes and forced into your home or through the city sewer. The stack acts as a chimney, venting these gases safely out through the roof.
2. Regulating Air Pressure: This is the function most homeowners misunderstand. For water to flow smoothly, it needs air behind it to push it down. Think of a straw: if you dip a straw in water and cover the top with your thumb, the water stays trapped inside. When you lift your thumb, the air rushes in, and the water flows out instantly.
Your plumbing stack is that open straw. It pulls fresh air in from the roof to replace the water rushing down the drain. Without this airflow, a vacuum forms in the pipes. This vacuum slows down drainage (causing gurgling) or can even suck the water out of your P-traps (the U-shaped pipes under sinks), breaking the seal that keeps sewer smells out of your house.
In short, the stack allows your plumbing to breathe. If your stack freezes, your drains will struggle to flow, and your house may start to smell.
Why Plumbing Stacks Freeze in Winnipeg
In Winnipeg, frozen plumbing stacks are common during the cold winter months. Your plumbing stack is essentially a chimney for your drainage system, constantly venting warm, moist air from hot showers, dishwashers, and sinks out through your roof.
The problem arises when this warm vapour exits the pipe and collides with Winnipeg’s extreme winter air (often -30°C or colder). Instead of drifting away, the moisture in the air condenses and freezes instantly upon contact with the rim of the pipe. Over several days of deep freeze, this ice accumulates layer by layer until it forms a cap that completely seals the pipe.
Older homes like those found in Winnipeg’s historic neighbourhoods (St. James, Fort Rouge, St. Vital, St Boniface, Transcona etc.) of are particularly vulnerable for two reasons:
Pipe Size: Older homes often use smaller vents, which can bridge over with ice much faster than modern pipes.
Insulation: In many older attics, the stack pipe is uninsulated, leading to a greater likelihood of freezing.
Symptoms: How to Know if Your Stack is Frozen
Symptom 1: The Smell. Sewer gas trapped inside the pipe is forced back through your P-traps into the house.
Symptom 2: The Gurgle. When you flush your toilet, the water struggles to go down, pulling air through the sink trap nearby, causing a gurgling sound.
Symptom 3: Slow Drainage. Sinks and tubs take forever to empty because of a vacuum within the system.
The easiest way to identify if your plumbing stack is frozen is to look at it. It should be free of ice and snow cover to allow gasses to exit the home and air to enter the plumbing system.
Watch our video for a visual aide on how this works.
Please note: Climbing on your roof in winter can be a very dangerous activity and should only be attempted by experienced personnel. We do not recommend anyone climb on their roof during winter but if you choose to do so use extreme caution!
DIY Diagnosis & Temporary Hacks
Online you will find numerous hacks on how to deal with this issue yourself. Do not do these!
The first one is the ‘look up test’. By standing on the ground and looking for your plumbing stack you may be able to see an ice cap on the pipe. This could indicate a clogged penetrating stack. This method can lead to a false positive that can cause you to waste resources. Do not do this.
People online will also tell you that you can open the hatch to your attic in order to let warm air into your attic to thaw the penetrating stack. Never ever do this. This will allow moisture into your attic and can cause irreparable damage to your house.
The third ‘hack’ is to dump hot water on the frozen pipe. Never do this. This can cause your pipes to crack and it puts you at risk of bodily harm. Do not attempt to thaw your stack yourself without a professional diagnosis and professional help.
When to Call the Pros
Ignoring that sewer smell isn't an option, it is unpleasant and can be hazardous to your family's health. However, trying to fix it yourself also comes with risk. Winnipeg roofs are slippery and unpredictable in winter, and no home repair is worth risking a fall.
At Next-Gen Plumbing and Heating, we keep you safe on the ground. Our team is fully equipped with safety equipment and safe work practices to access icy roofs safely and securely. Once on your roof we use professional grade tools to melt the ice cap gently and effectively without damaging your plumbing.
We can also recommend solutions to replace older plumbing and to keep your penetrating stack from freezing again the next time that it is cold.
Stay warm and safe inside. Let Next-Gen Plumbing and Heating handle the icy heights.
Call us today at 204-292-7144 or book online for emergency frozen stack thawing.