23 February Overhead shot of a person using a sink

Why Do My Drains Smell?

Posted by PlumbWize

A plumbing system that is in good working order should do two things: supply clean water to your home and direct wastewater away. For the latter function, various kinds of drains in your home or property play a critical role. For example, the drains in your sinks, showers, bathtubs, and toilets all channel wastewater away. Because of this, they may emit bad drain smells from time to time.

If you’re concerned about unpleasant drain smells in your home or property and are wondering what to do about it, you’re in the right place! In this guide, we will cover the causes of bad drain smells for the various drains in your home as well as the next steps you can take to avoid drain smells in the future.

Let’s get started!

A plumber checks a shower drains smell

Common Reasons Why Sink Drains Smell Bad

There are three common reasons why sink drains smell bad. First, the smell can be coming from a clog in the drains. Kitchen faucet drains are particularly susceptible to this since food, grease, and other organic substances can build up over time and cause a partial or full blockage.

Second, it may not be a blockage at all, but instead a layer of decaying food, fats, and grease that are forming on the sides of the drain. Whether it’s a full blockage or just a layer of debris, bacteria can proliferate while the organic matter decays, giving off unpleasant drain smells. Mould can also form in the same environment and contribute to the unpleasant drain smell. Another related possibility is that scraps of food have gotten stuck to the blades of the garbage disposal.

The third reason why your sink drains are producing an odour is because sewer gases are wafting up the pipe. This can be caused by problems with the sink’s trap (the P or U-shaped pipe under the sink). If sewer gases are coming through, it can mean that the water in the sink’s trap has evaporated. This scenario is highly common if the sink hasn’t been used in a long time or if there is a problem with the sink’s plumbing drain vent.

Common Reasons Why Shower or Bathtub Drains Smell

The first reason why shower and bathtub drains smell bad is because of drain clogging, whether it’s a full or partial clog.

It may also be not a clog but a biofilm of decomposing debris and bacteria sticking to the sides of the drain. Soap scum debris is highly common in these drains, and though it’s a residue from soap, soap scum can actually be a food source for bacteria and mould. That’s right. Though no food particles are typically washed down shower or bathtub drains, there is still some organic matter that bacteria can feast on.

Similar to sink drains, when there is a problem with the trap of a shower or bathtub drain, sewer gases can also waft upwards. This is usually because of a dried up P-trap. However, another common reason why shower or bathtub drains smell like sewage is because of a sewer backup. In such scenarios, waste water cannot flow to the sewer properly when the toilet is flushed. It then flows back up and typically ends up at the lowest point (which can be the shower or bathtub drain).

Common Reasons Why Toilet Drains Smell

With toilets, it can be difficult to pinpoint if the smell is coming from a drain problem or if it’s because of a problem with the toilet’s wax ring. For the first possibility, water can evaporate from the P-trap and this can cause sewage gas to waft upwards – a common possible reason for all drain types.

The other probable cause is not a problem with the toilet’s drain but with its wax ring, the part that is used to seal the gap between the bottom of the toilet and the floor. When this wax ring wears out over time, it can allow sewer smells to leak through.

An individual cleans their kitchen sink drain

What Can Be Done to Avoid Smelly Drains

The first step to proper drain maintenance is to avoid putting inappropriate substances down the drain. By taking this precaution, you can avoid clogging, which is a common cause of smelly drains. This can also help to prevent the buildup of debris on the sides of the pipes. A few examples of this type of buildup include hair, dirt, and grease.

Another precaution that homeowners can take is to regularly clean their drains. By this we don’t mean harsh commercial drain cleaners that can potentially destroy pipes; the safest way for homeowners to clean their drains is by doing the following steps:

  1. Pour boiling water down the drain.
  2. Pour a mixture of 1 cup baking soda and 1 cup of vinegar down the drain.
  3. Wait for 5 minutes before pouring boiling water down the drain yet again.

Another option is to schedule regular drain maintenance by an expert plumber. An expert plumber would have tools that typical homeowners do not have and this allows the plumber to be able to clean the drains more effectively and thoroughly.

Reliable Drain Assessment and Maintenance For Your Property

PlumbWize is a leading provider of residential and commercial plumbing services in the areas of Burlington, Oakville, Hamilton, Milton, Ancaster, and Stoney Creek. Through our years of experience, drain problems are definitely one of the top plumbing issues that we deal with all the time – we’ve seen it all. Our expert plumbers will be able to quickly and easily troubleshoot any drain problems in your property and recommend the next best steps.

No plumbing concern is too big or too small for us to handle. If you’re worried about existing drain smells coming from your pipes we can help you get to the bottom of the problem and fix it for you – just give us a call!


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