Eliminating bathroom sink odours

Q: How can I get rid of the rotten egg smell that wafts up from the drain in our bathroom sink? We recently bought this house and I've used a lot of different products without success.

A: All drainpipes contain foul-smelling gases, and it's the job of the S-shaped bend in the pipes underneath your sink (called a trap) to prevent this from back drafting into your house. It's possible the drain trap wasn't installed properly and this is the reason for the odour. Peer down the drain with a flashlight. If you can see water, then chances are the trap is working. If in doubt, call in a plumber. A more likely source of trouble is a bacterial infection of your drain. Some readers I've helped in the past have found relief by dumping a 500 ml bottle of hydrogen peroxide down the drain at night, just before bedtime. Others have had to resort to undiluted laundry bleach to kill the critters. If your sink has an overflow port near the rim, be sure to pour disinfectant down this passage, too. Bacteria love this spot.