Renovation & Design

Have a certified plumber inspect smelly drain

Jean Levac / Ottawa Citizen files

Odours from sinks are generally caused by either sewer gas or mouldy decomposition.

Question: About a year and a half ago I had our bathroom completely renovated with a new tub, toilet, flooring and Ikea sink and vanity. Since November I have noticed a slight sewer smell coming from the sink. A friend suggested pouring Javex down the drain and running hot water to kill the smell, but I’m not sure that would be good for the pipes. I tried baking soda and hot water but it didn’t help. Any ideas? — Barb P.


Answer: Odours from sinks are generally categorized in one of two types, sewer gas or mouldy decomposition. While the mouldy smell may be minimized by simple cleaning, sewer gas is much more serious and will be a result of a plumbing drain defect. Determining which of these is the cause will dictate the appropriate remediation and likely require a call to a licensed plumber for repairs.

Smelling a little bit of stinky odour emanating from a bathroom sink can range from a minor issue to a more serious plumbing drain defect in design or installation. The first suspect would be hair and soap accumulation in the drain, trap, or overflow. Because the bathroom sink is regularly used for hand and fascial cleaning, shaving, and other personal hygiene and make-up functions it is susceptible to a large amount of debris accumulation. Most of this will be washed down the drain piping, but a substantial amount can accumulate inside the pipes, over time. For this reason, most drain traps are removable or have a drain plug at the bottom for periodic cleaning.

The first course of action when the sink starts to smell is to place a small container under the trap and remove the drain plug or entire trap assembly. Water held in the trap will quickly drain out, allowing manual cleaning of the trap and attached pipes. This can be a bit of a messy job, but with regular maintenance will only require removal of hair and soap debris with an old toothbrush and water. If an excess amount of gunk is found inside the adjoining pipes, a small plumbing snake may be used to help clear this out, as well. Once cleaned, the trap can be reassembled and the pipes flushed out a few times by draining a few sinks full of hot water. If the gunk inside the trap or pipes is inaccessible, then use of a chemical drain cleaner may improve the situation.

The next area that is often overlooked in relation to debris accumulation is the sink overflow. Most bathroom sinks have an overflow system, either integral to the sink or installed as part of the waste piping. This is visible as a small opening or hole near the top rim of the sink, which will prevent the sink from overflowing if the faucet is left on too long with the drain plug in place. If the sink is regularly filled near or above this threshold, a fair amount of the sink contents can drip or drain into this cavity or pipe. This can lead to a buildup of soap scum, hair, shaving cream, or other debris inside, just like the trap and drainpipes. This may be harder to clean than the trap, due to limited access, so pouring some chemical drain opener, and flushing several times with hot water, may solve the problem.

The other side of the page will be related to improper installation of the drain piping, or poor design of the sink and drain assemblies. Since you have recently upgraded the entire bathroom before noticing the offensive odours, this is a much more likely scenario. Too often I see improperly installed traps, sometimes with missing venting, in recently renovated bathrooms. This is often done by inexperienced homeowners and contractors, rather than Red Seal plumbers, who don’t know how to correctly install sink drains and vents. If this is done improperly, the water inside the trap may drain or siphon out, which will allow noxious sewer gas to escape the drains. This will be a true sewer smell, but the mouldy odour of plugged drains is often mistaken as such. Sewer gas vapours can be harmful to the occupants of the home, so differentiating between it and stinky trap odour is important.

Since you have purchased your sink and vanity from IKEA, there is another possibility for the source and type of odour. Many of the plumbing products from that store, and other similar retailers, are designed in Europe or other foreign countries. Unfortunately, the fittings and designs for some plumbing fixtures not made by North American manufacturers may not be fully compatible with our common drains. Especially under newer bathroom sinks in very shallow vanities I have seen unusual trap configurations that don’t resemble a common P-trap. Many of these may not drain as effectively as a standard trap and may be prone to filling up with debris, or poor venting. Even with assembly according to the manufacturer’s specifications, these may not perform as well as a standard drain, and could be the potential cause of your problems. This may only be determined and remedied by an experienced plumber, who should be able to change the drain assembly and adapt this properly for your bathroom.

Figuring out whether your smelly sink problems are the result of excess debris in the pipes and trap, or a defect resulting in sewer gas intrusion, is critical to addressing the issue properly. If a simple removal and cleaning of the trap and overflow does not solve the issue, calling a licensed plumber to evaluate the situation and repair or replace the drain assembly should terminate the offensive or noxious odours.


Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba ( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at




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