Sewer Odors in Bathroom

Sewer Odor in Bathroom TIPS

DEAR TIM: We recently have begun to notice a sewer odor from only one of the three bathrooms in our house. It might be the toilet, but it’s hard to tell. The smell is not constant and some times it is very strong. Everything in the house drains fine, including the toilet with the odor. Where can the odor be coming from? I have put a bacterial additive in the toilet but this does not seem to help. Is this serious? What can I do to fix the problem? Karen B., Watseka, IL

DEAR KAREN: The odor can be coming from numerous places. Often the source of the problem is simple, but in rare occasions the problem can be a serious plumbing flaw that is hidden behind a wall. I have found more often than not that the problem can be solved in just a few moments with a quart of water.

CLICK HERE to get FREE & FAST BIDS from local plumbers to STOP sewer gas odor.

sink p trap

Check Traps

See if all of the plumbing fixtures have water in the traps. Many people do not realize the purpose of the P shaped traps in the drain lines beneath sinks, tub and showers. Lots of people think they are there to catch rings and earrings from traveling down to sewers and septic tanks. They do this but they also keep sewer gas and vermin from traveling up and into your home. The standing water in a trap is an excellent barricade against sewer gas.

Plumbing fixtures or floor drains that get little use can loose this effective water seal. The water in the trap simply evaporates and/or it can be sucked from the trap by a clogged vent pipe or a poorly designed or installed pluming system.

Don’t Be a Fool!

You can be fooled when you look into a drain and see the reflection of water. Even though you see water, sewer gas can be passing over this small amount of water left at the very bottom of a trap. Tubs and showers in guest bathrooms frequently are the culprit. Often people will use a toilet or sink in a bathroom but the tub and shower go unused for months at a time.

Pour a quart of water in the sink and tub drains. This is plenty of water to fill the trap and provide the full water seal. If this is the problem, the odor should go away in a very short amount of time. If the odor is still present, then it is time to look at other possibilities.

BioFilm Odor

The inside surface of bathroom sink, tub and shower drains can also be a huge source of odors. Kitchen sinks frequently have similar odor problems. Almost all sinks have a piece of pipe called a tailpiece that extends from the bottom of the sink into the top of the p trap. This pipe is constantly exposed to the air in your bathroom.

All of the bacteria, dirt, grime, mold, etc. pass through this pipe on its way to the sewer or septic system. But often some is left behind. Over time a thick layer of slime starts to collect on the inside surface of this vertical pipe. Mold and bacteria can begin to grow and some produce noxious odors.

This slime is a biofilm. Mold grows FAST in this slime. When you run water, the water touches the ripe mold and it EJECTS spores into the air. The explosion of the spore into the air is caused by a foul gas the mold creates. That’s the source of the odor in many cases – the tiny amount of propellent used by the mold to send a spore out into the air in your house!

CLICK HERE to get FREE & FAST BIDS from local plumbers to STOP sewer gas odor.

Oxygen Bleach and Bottle Brush

Because of the fixed metal parts at the bottom of sink and tub drains, it is virtually impossible to completely clean these pipes while they are in place. Often you can take apart the drain assembly and clean the inside of this pipe in a jiffy. Pay attention to the rubber washers and gaskets as you take them apart. If the drain is old, these parts often need to be replaced with new ones to make sure the drain is leak free once you re-assemble it.

Oxygen Bleach

Stain Solver is MADE in the USA with USA ingredients that are food-grade quality. CLICK THE IMAGE to order some NOW.

I clean out the pipe under my shower strainer using a bottle brush and Stain Solver certified organic oxygen bleach. I mix two tablespoons of Stain Solver with one quart of HOT tap water and stir until dissolved.

I pour this solution into the shower drain and use a bottle brush to scrub the side walls of the pipe above the water in the trap below.  After rinsing the sidewalls of the pipe with clear water, pour any remaining Stain Solver solution into the drain so it can clean the sidewalls of the pipes that form the p-trap under the shower.

You can also use the Stain Solver and the bottle brush to clean the sidewalls of the tailpiece pipe that leaves the bottom of vanity sinks.

You’ll just have to take out the stopper so you can get the bottle brush down the hole in the bottom of the sink. It’s easy to remove the stopper using an adjustable pliers. Just turn the nut on the back of the tailpiece under the sink.

bottle brushes

These are typical bottle brushes. You want one that has a diameter of at least 1 and 1/4 inches. A 2-inch diameter one is great for shower drains. CLICK THE IMAGE TO BUY THESE NOW.

Biofilm can also develop on the inner sides of the overflow passage in a vanity sink. To clean this out, all you do is use a turkey baster to squirt large amounts of Stain Solver solution down the overflow holes.

Squirt some down at first and then walk away from the sink. Come back every 15 minutes for an hour and do a few more generous FAST squirts sending as much solution as possible down the overflow holes.

If after all of this the odor persists, the problem may be a serious plumbing problem. The toilet seal may be broken. A hidden vent pipe may have cracked. A plumbing professional has the tools, equipment and know-how to often quickly diagnose problems like this.

CLICK HERE to get FREE & FAST BIDS from local plumbers to STOP sewer gas odor.


CLICK HERE to have me, Tim Carter – founder of, CALL YOU on the phone to SOLVE your sewer gas problem. I’m a master plumber and do phone consults for homeowners about sewer gas each week.

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