You hop in the shower to get fresh and clean, not to smell something gross coming from the drain. Shower drain smells can result from odor-causing bacteria that feed on debris in the pipe. Some of these anaerobic bacteria live in fetid water in the P-trap and produce hydrogen sulfide gas, which smells like sewage or rotten eggs. Other foul odors can also be caused by the debris itself, such as hair or soap scum buildup. Mold can also grow on the soap and give the drain a musty smell or mildew odor. Thoroughly cleaning the drain or ensuring the P-trap and plumbing vent are working properly can help that sweeten that smelly shower.
How to Stop Shower Drain Smells
1. Remove the Drain Strainer
The drain strainer (the perforated drain cover) itself has to be removed for a deep clean. Most shower strainers are attached with a single Phillips screw. After removing the screw with a screwdriver, you may have to pry up the strainer — do this with a flat-head screwdriver. If you don't see a screw, all you have to do is pry off the strainer.
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2. Clean the Strainer
The first thing you'll notice after removing the strainer is a layer of hair and scum on the underside. Pull on a pair of rubber gloves and pull off the hair, scum, and grime, using a sponge and a cleaning solution or warm, soapy water or a mix of disinfectant and water.
3. Clean the Drainpipe
If you look down into the drain you'll see the same scum coating the drainpipe. Pull out as much hair as you can, using your fingers, an old toothbrush or a plastic drain cleaning tool, such as a Zip-It. You can also use a foam paint roller cover — without the roller handle — to clean the pipe. Soak the roller in soapy water, insert it in the drain and rotate it like a sponge. Rinse and clean again until the roller picks up no more scum.
4. Deodorize the Drain
You can disinfect the drain by pouring a 50-50 solution of household bleach and water into it. The bleach will flow down the sides of drainpipe but will not likely kill all the odor-causing organisms. As an alternative or a secondary measure, you can pour one cup of baking soda in the drain, followed by a cup of white vinegar. Cover the drain and let the mixture fizz inside the pipe like a science fair project for a few minutes, then flush with hot water. Repeat if needed to get rid of any lingering smells.
Preventing Shower Drain Odors
When it comes to shower odors, the main culprit is soap. You can't stop using soap in the shower, but you can prevent it from building up and becoming a problem by pouring boiling water into the drain once a week. If you suspect that soap is building up, dissolve it with an enzyme-based drain cleaner, and then add the water.
You Might Have a Dry P-Trap
The P-trap is U-shaped pipe at the bottom of the straight pipe leading down from the shower drain opening. The trap holds a small amount of water that fills the bend of the pipe. This water effectively seals off the pipe from the drainage system and sewer pipe downstream of the shower. If you haven’t used the shower in awhile, the water in the trap may have dried up so it’s no longer sealing out sewer gases, and thus the smelly shower drain. The solution is simple: just turn on the shower faucet and let it run for a few minutes. This will fill the trap with water, shutting off the sewer smell.
If you detect a strong sewer smell from the shower, especially after flushing a toilet or using the washing machine, your plumbing vents may be blocked. When this happens, suction in the pipes from flowing water can empty the P-trap. Clearing debris from the roof vent usually solves this problem. If the blockage occurs in winter, the roof vent may be blocked with ice or snow. If this is the case, go into the attic and point a hairdryer at the vent at the point where it exits the roof to melt the ice. Cleaning the blockage may solve the problem.
If the vent problem is not related to ice or snow, there may be a clog in the vent caused by an animal's nest or even leaves or other debris. You can have a plumber clear the vent, or you can take the DIY approach and auger the vent from the roof using a 25-foot drain snake. Just work the snake straight down; you shouldn't need to pass through any bends. The main vent pipe (called the vent stack) turns into the house's main drain, which becomes the sewer line leading away from the house, bu you shouldn't need to go into the drain. If you get past the level of the shower and haven't hit a clog, the bad smell in the shower is related to something else.