Why does my shower drain smell?

Updated February 21, 2017

Most homeowners will quickly notice any odours emanating from a shower drain, especially if the shower is used frequently. Some odours may creep up on the homeowner in a gradual manner, growing stronger over time, while other odours may suddenly waft from the drain. Shower drains can emit odours ranging from the innocuous to potentially hazardous for a variety of reasons.

Chemically Treated Water

Occasionally, your shower drain may smell strongly of bleach or chlorine. The odour is actually coming from the water, but the volume of water coursing through the drain makes the odour seem to originate in the drain. Even when the shower is dry, the pipes beneath the drain retain moisture that may be tainted with a chemical odour. The chlorine used by water treatment plants to treat water supplies for contaminants is the cause of this odour. Management companies, such as the North Texas Municipal Water District, treat water in the fall or winter months when the temperature of the water is lower to prevent an accumulation of chloramine residue in water during the summer months. This chemical odour, although strong at times, isn't unsafe, and it should subside in about a month. Check your local water company's website or publications for scheduled treatment dates.

Mold and Mildew Accumulation

Mold and mildew develop in perpetually wet environments. Showers that are used by multiple people multiple times a day are likely to accumulate mildew or mould in or around the shower drain if the drain is never dry or is dry for only a short duration. Odour in a shower drain caused by mould actually originates from mould spore gas. Mold and mildew emit an odour that smells musty or sour. Pouring bathroom disinfectant or household plumbing or drain disinfectants down the drain may help kill the mould or mildew growth and eliminate the odour. Keep the drain as dry as possible to reduce future mould and mildew accumulation.

Pipe Corrosion

Plumbing pipes can corrode if the pH level of the water supply is too low. The low pH level can lead to deterioration of the pipes leading to and away from the shower drain. Pipe corrosion emits a coppery, metallic odour from the shower drain. Home improvement or plumbing supply stores sell pH test kits allowing you to test your water. Pickett Plumbing recommends a pH level of 7.0. A pH level below 7.0 can result in pipe corrosion, which leads to odours, discoloured water and staining of your sinks, showers and toilets. If your water tests out with a acidic, low level, you may need to treat your water with water softeners or a water softener system.

Biofilm Accumulation

Biofilm is a film of organic materials that accumulate inside of plumbing pipes and the shower drain leading into the pipes. This slimy film is comprised of bacteria that produce odours. Removing the biofilm from drains and pipes requires the removal of the shower drain strainer cover and cleaning. Clean the drain cover with soap and water and a brush. Use a plumbing or bottle brush to clean as far down into the shower drain pipe as possible with shower cleaner or liquid dish detergent. Biofilm often manifests as a black slime.

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About the Author

Louise Harding holds a B.A. in English language arts and is a licensed teacher. Harding is a professional fiction writer. She is mother to four children, two adopted internationally, and has had small businesses involving sewing and crafting for children and the home. Harding's frugal domestic skills help readers save money around the home.