Properly constructed and maintained plumbing will prevent sewer smells from entering your home or business through pipes.
How Plumbing Works
The plumbing system inside your home or any building consists of a network of pipes, vents and traps that carry off liquid and solid waste. These pipes, vents and traps are the least visible and least glamorous elements of your home’s plumbing, but the system is very important. Each plumbing fixture (toilet, sink, shower, floor drain, etc.) is connected to this system of pipes that carry the wastewater to the public sewer. The system safely removes waste for treatment and provides a critical barrier that keeps sewer gases from entering your home.
How Vents and Traps Work
At first glance, drains seem to work even without traps and vents. Plenty of do-it-yourselfers leave out these key components, without understanding their importance.
Why are vents and traps so important?
- A trap is installed for each plumbing fixture and holds enough water to form an airlock that prevents sewer gases from entering the building.
- Vents are required to be installed to allow sewer gases to flow up the solid vent stack and exit the vent outside, typically above your roof, without coming into your home through plumbing fixtures.
Vents equalize pressure to a
id drainage and allow sewer gases to escape to the outside air.
Without a properly functioning trap and vent, high or low pressure in the drain may allow sewer gases to enter the building.
The vent system allows outside air into the drain system to keep vacuums from forming in the drains. Think of vents as upside-down drains with gases rising in the pipes in the same way that water flows down them.
High Pressure Risks
- Without venting, high pressure in the drains may force sewer gas out through traps and toilets.
- You will probably hear gurgling and bubbling in the fixtures.
- You may also smell the bacteria odour mixed with sewer gas.
Low Pressure Risks
- Without proper venting, low pressure in the drains may cause siphoning in the traps whenever you drain fixtures.
- If the traps are dry, sewer gas vents directly into the house.
Frequently Asked Questions
| I have sewer smells, what do I do now? |
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There are a variety of reasons that sewer smells may be entering a home or business. These include:
- A lack of required traps or vents. Every fixture should have a trap and a vent pipe to keep smells from entering the home. If traps and vent pipes are missing, you may need the help of a plumber to install them immediately.
- The seal around the toilet may be broken. This allows water to siphon or dry out the traps and thus allowing smells to enter the home. There could be an air leak at the wax ring of the toilet or in the vent pipe. Rotted or damp wood can also cause the smell. Check to see if the toilet is tightly sealed to the floor. Grab the bowl of the toilet and try to slide it from side to side. It should resist a few pounds of pressure. If the toilet rocks from side to side, the wax ring has failed. You may need the help of a plumber to fix these problems.
- The trap may be dry. Pouring a quart of water into all sinks, showers/tubs and floor drains may correct this problem. All drains to a sewer system have a “P” shaped trap that is usually filled with water. The trap provides a seal to keep out sewer gas. If your basement floor drain is rarely used, water evaporates from the trap over time. Eventually the seal is eliminated, allowing sewer gas (and smell) into your house. The solution is easy: pour water into the drain.
- The trap under the basin may not be holding enough water and is allowing sewer fumes into the room. You may want to inspect your trap and be sure it holds enough water.
- The trap may be cracked or broken if you have an old “house trap” in your basement which allows smells to seep through the cracks and into your home.
- Debris may be inside the inner chamber of the sink. If the smell is noticeable mainly around a sink, try flushing a strong cleaner and bleach down the sink’s overflow (the small hole(s) inside the bowl near the rim). When the sink fills to near overflowing, water is routed through an inner chamber to the drain. Debris can collect inside the inner chamber, causing odour.
- There may be a small leak in one of the vent lines of the plumbing system, or a small leak around the base of a toilet or other fixture. You may need the help of a plumber. Check for loose fitting, corrosion, or holes in vent piping. Also, check the top side of horizontal drain pipes. If the top is rusted, it may never leak liquid, but it will leak sewer gas. Drain lines made of copper, steel or cast iron may exhibit this problem.
- There may be cracks in your piping if they are older cast iron piping, which allows the smells to seep into your house. Older cast iron piping has a habit of forming a crack along the topside of the pipe over time, and this could be where your smell is coming from. You may need to inspect every inch of piping for cracks or openings where the smell is coming from, and then make any necessary repairs. If the entire length of pipe is cracked (quite common), you should replace it using PVC drain pipe of the same size, with no-hub couplers to fit the pipe into place.
- There may be a clogged vent (quite common). You may need the help of a plumber or a handyman to disconnect the vent pipes inside your home and clean your vents all the way through the roof.
- The vent outlet outside may be clogged (eg. bird nest, bee hive).
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How do I locate the places where sewer gas is entering my home?
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- Check all of the traps in your house to make sure they are full of water and not leaking.
- Go on the roof or have a plumber or handyman go on the roof and check all of your vent stacks to see if it is clogged or if a dead rodent is lodged in one of the vent pipes.
- Re-install the bowl-wax rings on the toilets in your house, sometimes they get old and let sewer smells seep in.
- If you are on slab foundation, check to see if you have any sewer-leaks in your pipes going into your foundation or under your slab foundation. (You may need a smoke test for this.)
- Get a smoke test done on your drains. A plumber/drain cleaner will cap off all drain vents on your house, and blow smoke in your drain, waste, and vent system; wherever you see smoke in your house, that is where the sewer gases can enter your house from.
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