Shower Smells Like Rotten Eggs? 6 Causes and How to Fix Each

You step into the shower and that smell hits you. Rotten eggs. Sulfur. Wet swamp. It is not just gross, it usually means something is sitting somewhere it should not be. The good news: in 9 out of 10 bathrooms, the cause is one of six things, and most fixes are quick and cheap.

Sniff once more before you start. Does the smell come from the drain itself when you bend down, or does it hit when the hot water runs? That single clue cuts the list in half.

Start With These 30-Second Checks

1. 1Run hot water for 30 seconds, then sniff. Smell only with hot water = water heater issue. Smell anytime = drain issue.
2. 2Pour a cup of water down the drain. If it gurgles or smells worse, the P-trap is the suspect.
3. 3Pull back the shower curtain or remove the bath mat and smell those. Mildew on fabric can mimic sulfur.
4. 4Check when you last used the shower. Drains that sit unused for 2+ weeks lose their water seal.

1. Dry P-Trap (Most Common)

Every drain has a U-shaped pipe under it called a P-trap. It holds a small amount of water that blocks sewer gas from rising into your bathroom. If the shower has not been used for a few weeks, the water in the trap evaporates and the gas pushes through.

1. 1Run the shower for two full minutes to refill the trap.
2. 2Pour a quart of plain water directly down the drain afterward to fully reseal it.
3. 3If you have a guest bathroom or basement shower you rarely use, run them once a month.
4. 4For long absences, add a tablespoon of mineral oil after running water. Oil slows evaporation for months.

2. Biofilm Buildup in the Drain

Soap scum, hair, and skin cells coat the inside of your drain pipe over months. Bacteria feed on that sludge and release hydrogen sulfide gas. That is the rotten egg you smell, especially when warm water hits the buildup.

1. 1Remove the drain cover (usually two screws or just lifts out).
2. 2Pour one cup of baking soda down the drain, then one cup of white vinegar. Cover the drain and wait 15 minutes.
3. 3Flush with a kettle of boiling water (only for metal pipes, never PVC).
4. 4For stubborn buildup, use a flexible drain brush or hair snake to physically scrub the inside of the pipe.
5. 5Repeat monthly to prevent regrowth.

3. Sulfur in the Water Heater

If the smell only appears when you run hot water, your water heater is probably the source. The magnesium or aluminum anode rod inside the tank can react with sulfate bacteria, producing hydrogen sulfide. The colder side stays fine because that reaction needs heat.

1. 1Confirm by running cold-only water. No smell = water heater is the cause.
2. 2Flush the tank: shut off the heater, attach a hose to the drain valve, let it run until clear.
3. 3If smell returns, replace the anode rod with an aluminum-zinc alloy rod (about $30). The zinc neutralizes the bacterial reaction.
4. 4For well water, install a softener or chlorinator upstream of the heater.

4. Mold or Mildew on Shower Surfaces

Pink slime in the grout, black spots in the silicone, or fuzzy mildew under the bath mat all give off sulfur-like odors as they grow. People often blame the drain when the actual source is six inches up the wall.

1. 1Inspect every grout line, silicone seam, and corner for pink, black, or green patches.
2. 2Spray affected areas with hydrogen peroxide (3% from the drug store). Let sit 10 minutes, then scrub with an old toothbrush.
3. 3For deep mildew in silicone, the only real fix is to dig it out and re-caulk.
4. 4Squeegee the walls after every shower to prevent regrowth. Mildew cannot grow without standing moisture.

5. Cracked or Disconnected Vent Pipe

Every drain in your house connects to a vent pipe that runs up through the roof. The vent lets sewer gas escape outside instead of being pushed back into your bathroom. If that pipe cracks, gets clogged with leaves, or comes loose in the wall, the gas finds an easier route. Through your shower drain.

1. 1Listen for gurgling when other drains in the house run. Gurgling means the vent is partially blocked.
2. 2Look on the roof for the vent stack pipe sticking up. Make sure nothing is covering it (leaves, bird nest, ice).
3. 3Inside the wall, you typically need a plumber for this one. It is the only fix on this list that often is not DIY.
4. 4While you wait, pour a cup of bleach diluted in water down the drain weekly to mask the smell.

6. Hidden Leak Under the Shower Pan

If the shower pan or surrounding floor has a small leak, water collects underneath and feeds bacterial growth in subflooring. You will not see standing water, but the smell rises through the drain area. This one is rare but serious because hidden water damages joists.

1. 1Check the ceiling directly below the shower for water stains or soft spots.
2. 2Run your hand along the bottom corners of the shower where the floor meets the wall. Soft, spongy drywall confirms a leak.
3. 3Push lightly on the shower floor itself. If it flexes more than a millimeter or two, the pan is compromised.
4. 4This requires opening the wall or floor to dry out and re-seal. Call a contractor before the damage spreads.