Why Does My Drain Smell? Causes and Fixes

A homeowner guide from Drain Edge Rooter, a licensed plumbing company in Rialto, CA (C-36 #1078977). Open 24/7, call anytime: (909) 927-3194.

A bad smell coming from a drain is more than a nuisance. Sometimes it is just buildup in the pipe, but a sewer odor can also mean a dry trap, a venting problem or a leak in the drain line. The good news is that many drain odors have simple fixes.

1. A dry P-trap

Every drain has a trap, a curved section of pipe that holds water and blocks sewer gas from coming into the house. If a fixture is not used for a while, such as a guest bathroom shower or a floor drain, the water evaporates and sewer gas comes through. Fix: run water in the fixture for a minute. For floor drains you rarely use, pour in water every few weeks.

2. Buildup in the drain

Hair, soap scum, grease and food residue collect inside drains and the overflow channel of sinks, where bacteria grow and smell. Fix: remove and clean the stopper, scrub the overflow opening with a small brush, and flush the drain with hot water and dish soap. Clean the P-trap if the smell stays.

3. The garbage disposal

Food stuck under the splash guard and on the grinding chamber is a common source of kitchen sink odors. Fix: turn off the power, scrub the underside of the rubber splash guard, then run the disposal with cold water and a handful of ice.

4. The washing machine or dishwasher

A musty smell near the laundry may come from the washer itself or from the standpipe. A dishwasher with a clogged filter or a sagging drain hose can also smell. Clean the appliance filter and make sure drain hoses have a proper high loop or air gap.

5. Venting problems

Plumbing vents let air into the drain system so traps stay full. A blocked vent can cause gurgling drains and traps that siphon dry, which lets sewer gas in. Vent problems usually need a plumber to diagnose.

6. A cracked or leaking drain line

If the smell is constant, strongest near a wall or floor, or there are damp spots, the drain line itself may be cracked or a joint may have failed. In older Inland Empire homes, cast iron drain pipes can crack and corrode over time, and clay sewer lines can separate at the joints.

ABS drain repair with no-hub couplings under a house, old cast iron pipe visible, by Drain Edge Rooter — Under-house repair: a failing cast iron drain section replaced with ABS and no-hub couplings.

7. A rotten egg smell from hot water only

If the smell only comes from hot water, the cause is often the water heater rather than the drain. A reaction with the tank’s anode rod can create a sulfur smell. A plumber can check the anode rod and flush the tank.

Quick troubleshooting checklist

Run water in every rarely used fixture and floor drain.
Clean the stopper, overflow and P-trap of the smelly sink.
Scrub the disposal splash guard.
Clean the washer and dishwasher filters.
Check whether the smell is only from hot water.
Note whether drains gurgle when other fixtures run.
Look for damp spots near walls or floors.

Pay attention to when and where the smell shows up. An odor in one rarely used bathroom points to a dry trap. An odor through the whole house, or one that comes with gurgling, points to venting or the main line. Those details help a plumber find the cause faster.

When to call a pro

Call a plumber if the smell is strong or constant, if you also have slow drains or gurgling, if you smell sewage outside, or if cleaning the fixture does not help. Sewer gas should not be ignored. Drain Edge Rooter is open 24/7, so call anytime at (909) 927-3194.

Related services and areas

Related services: Drain Cleaning, Sewer Camera Inspection, Sewer Line Repair. We serve the whole Inland Empire, including plumber in Rialto, plumber in Highland, plumber in Redlands, plumber in Bloomington. See all homeowner plumbing guides.