You walk into your bathroom and crinkle your nose as you detect the faint smell of sewage coming from ... somewhere. At first, you think you're imagining things. You lean closer to the sink, the shower drain and the toilet as you try to identify the source of the offensive odor. You squeeze some cleaner into the toilet bowl and give it an extra scrub, even though you're certain you just cleaned it yesterday. The fragrance of the cleaner temporarily masks the smell, and you leave the room. Later, you catch another whiff as you walk past the bathroom door. This time, the smell is unmistakable, and no amount of scrubbing, running the fan or spraying air freshener is able to resolve it. So why is there a sewage smell in your bathroom? How to Get Hard Water Stains Out of Your Toilet How to Prevent Odors in Toilets The bad news is that any number of things can cause a sewage smell in your bathroom, and it can be difficult to pinpoint the source of the odor. Besides the obvious unpleasant smell, the methane in sewer gas can actually be flammable in large quantities, and breathing it in can be hazardous to your health.

The good news: Once you finally identify the reason for the sewage smell in your bathroom, it's often relatively simple and inexpensive to correct. Delta Tub Faucet Won'T Turn OffWant your clean-smelling bathroom back? Faux Wood Beams DenverAir exchange through the plumbing vents keeps sewer gases at bay. Dixieland T ShirtsThe distinctive smell of sewer gas wafting through your home means something is wrong with the plumbing. Odors can signify a toilet leak or a crack in one of the plumbing vent pipes. Even when all the vent pipes are intact, there's still a good chance that blocked vents are responsible for the odors. When they aren't allowing air into the drains, flowing water can create a vacuum that sucks out the water in the bottom of P-traps meant to keep the gas behind it in the pipes.

To fix the problem, you need to clear the vents. Locate the source of the odor. If it's coming from a toilet, the toilet may need servicing. If you smell the odors at a fixture drain, the vents are probably blocked. Smells coming from the wall signify the need to repair cracked or disconnected vent pipes. Pull off the toilet if the smells originate there. Do this by turning off the water, draining the tank and unscrewing the toilet bolts with a wrench. Examine the subfloor for moisture damage. If you see any, repair the damaged sections. Raise the flange if the top is more than 1/2 inch below the surface of the flooring. When the flange is too low, the wax ring can't seal the waste line, and sewer gases can pass through it. Unscrew the flange with a screwdriver, place a flange extender on top of it, and replace the screws to hold the flange and extender to the subfloor. Replace the toilet when you're done. Clear the vents if the odors originate from a fixture P-trap. You are able to smell the gases at that fixture because the trap has been emptied by a vacuum in the waste line.

Confirm this by pouring water down the sink to fill the trap and then flushing the nearest toilet. You'll probably hear sucking and gurgling sounds coming from the fixture. Climb on the roof with an extension ladder and clear debris from the vent opening. The vent is usually situated just above the main bathroom. It may be blocked by leaves, sticks or even a dead bird. Pour water down the vent with a garden hose if the opening isn't blocked. The water may clear the obstruction. If not, it overflows from the vent opening. Insert a sewer auger into the vent and push it down as far as you can if the water overflows. Crank the handle to work the auger through the blockage. When the blockage has been cleared, the water standing in the vent pipe will drain. Spray more water to make sure the vent is open. Examine the vent pipes in the wall if the smell originates from there. The pipes may be accessible in the attic or basement, but if they are running through the main part of the house, you'll probably have to remove wallboard to get to them.

Re-glue loose joints in the vent pipes with plastic pipe cement. Because vent pipes don't carry water, plumbers often forget to glue them, and odors can seep from unglued joints. Repair cracked or failing fittings by cutting them out with a hacksaw and gluing in replacement pipes and fittings. Things You Will Need Wrench Screwdriver Flange extender Extension ladder Garden hose Sewer auger Plastic pipe cement Hacksaw Tip Warning References Renovation Headquarters: Sewer Gas Odor In Your HomeCheck This House: Plumbing Vent Problems in Your House | Q: DEAR TIM: My husband installed a new gasket on the toilet in our master bathroom as part of adding a new ceramic tile floor. He's pretty handy, but I soon noticed a sewer gas odor in this room. There wasn't an odor before. He can't smell it, and I'm reluctant to have him do the job over. The toilet doesn't move and the caulking is perfect, so I can't imagine where the odor is coming from. What needs to be done to correct this? -- Vikki H., Henderson, Ky.

A: DEAR VIKKI: The toilet bowl gasket was not installed correctly. The smoking gun is the fact that no odors were present before your well-intentioned husband started the bathroom remodeling job. I'm afraid that he will need to start over, but we need to discover what he did wrong so this second attempt gets it right. The source of the odor is probably the holes where the toilet bolts pass through the ceramic toilet bowl base, which are usually not sealed. The sewer gas that's wafting past the toilet wax gasket can easily seep past the bolts and the decorative caps. The caulking between the base of the toilet bowl and the floor won't stop the odor if these bolt slots are unsealed. The seal between the toilet flange -- the transition fitting that allows you to connect the toilet to the drain piping -- and the toilet bowl is critical. Not only odors, but also vermin and water can get through this joint if the toilet gasket is not making positive contact. When replacing a toilet gasket, you need to pay close attention to many details.

Homeowners and some rookie plumbers fail to look at the recessed area under a toilet bowl. This part of the toilet is often about three-quarters of an inch deep. This distance is measured between the bottom of the toilet bowl (i.e., where it contacts the finished floor) and the underside of the unglazed porcelain outlet where the wastewater exits the toilet. The next thing you should pay attention to is the thickness of the toilet wax gasket. Most of them are no more than seven-eighths of an inch thick. I've measured many, and some are just three-quarters of an inch thick. For a toilet gasket to seal properly, the space between the underside of the unglazed fixture, where the water exits the toilet, and the top of the toilet flange should be no more than a half an inch. This means the top surface of the toilet flange should be at least a quarter of an inch above the finished floor surface. The top of the flange should be level, and the flange must be secured to the floor so it doesn't move.

It's possible that your husband wasn't aware of this important point. The top of the toilet flange may have been flush with the floor or even sticking up too high. I've seen toilet flanges installed by inexperienced plumbers and homeowners that were an inch or more above the finished floor. When a toilet flange is too high, a poor seal can result because all of the wax gets squeezed out between the toilet and the flange as the toilet is secured to the flange. In your case, I think an autopsy will reveal that the toilet flange got buried by your new flooring. This is a very common mistake. A homeowner may install ceramic tile in place of a sheet vinyl floor. By the time ceramic backer board is put down and the new tile laid, the top of the toilet flange can be well below the finished surface of the floor. When this happens, it's entirely possible the toilet gasket never even touches either the flange or the underside of the toilet bowl. Be sure your husband removes the toilet and discards the gasket he just installed.