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Bathroom

How to Clean a Bathroom Sink Overflow Hole

To clean a sink overflow, scrub the opening and the first few inches of the channel with a small, narrow brush, flush it with hot water, and repeat until the brush comes out clean. The overflow is the hole or ring of small holes near the top of the basin. Water from splashes and rinses runs through it, but it rarely gets cleaned, so soap scum, toothpaste, hair, and a gray slime build up inside. That buildup is a common reason a bathroom sink smells musty even when the drain seems fine.

What you need

A narrow brush that fits the opening and flexes a little. The Sink and Overflow Detail Brush has a small head made for overflow holes, sink rims, and tap bases.
A funnel or a small cup, and hot tap water.
Baking soda and white vinegar, or plain dish soap.
A cloth for the rim and basin. A Microfiber Cleaning Cloth Set lets you keep one cloth for the bathroom only.
Rubber gloves, if you would rather not touch what comes out.

Step by step

Clear the drain first. Lift out the stopper if it comes out, and pull any hair from the drain, so the water you flush has somewhere to go.

Brush the opening. Work the brush into the overflow with a twisting motion, pull it out, and rinse it under the tap. The first pass is usually the dirtiest. Repeat until little or nothing comes out on the bristles.

Flush. Use the funnel or cup to pour hot water slowly into the overflow. Hot tap water is enough for most sinks. Avoid boiling water if your pipes are plastic or the basin is a cultured marble or composite material.

Deodorize if it still smells. Funnel about two tablespoons of baking soda into the overflow, follow with half a cup of white vinegar, and let it fizz for 10 to 15 minutes. Brush once more, then flush with hot water. If you have no baking soda, a little dish soap and hot water also works.

Finish the basin. Wipe the rim, the area around the overflow, and the base of the tap with a damp cloth, then dry it so water spots do not form.

Safety and what to avoid

Never mix bleach with vinegar, ammonia, or other cleaners. The fumes are dangerous, and the overflow channel connects to the drain, where other products may still be sitting.
If you recently used a chemical drain opener, flush with plenty of plain water and wait before adding anything else.
Skip abrasive powders on glossy porcelain or composite rims, and test anything new on a hidden spot.
Do not force a stiff wire into the overflow. Some have a tight bend or a plastic insert that can crack.
Rinse the brush after each use and let it dry fully. Do not leave it standing in a cup of bleach.

How to tell it worked

Run the tap and sniff close to the overflow. If the musty smell is gone and the brush comes out clean, you are done. Pour a cup of water into the overflow; it should drain away freely without gurgling back.

If the smell returns within a day or two, it may be coming from the drain or the trap under the sink rather than the overflow. In a sink you rarely use, the trap can dry out and let sewer air through; running the tap for a minute refills it. A persistent sewer smell, slow drainage after cleaning, or water dripping inside the vanity cabinet is a job for a plumber, or for the landlord in a rental. Some sinks, including many vessel sinks, have no overflow at all, so you can skip this job entirely.

Make it a habit

Once the channel is clean, a quick pass with the brush and a cup of hot water every two to four weeks keeps the slime from coming back. When you clean the whole bathroom, do the overflow before you wipe the basin, so anything that drips out gets wiped up in the same pass. The Bathroom Detail Cleaning Kit covers the other fiddly spots in the same room, such as tap bases and fixture seams.