Help! My House Stinks

by Tom Feiza,

Well, it may not actually stink but we often experience unwanted odors in our homes. Their source can be difficult to locate. Let's explore the "secret solution" to several common odors. Home inspectors can use this information to help customers trace down smells and provide practical solutions.
When you detect a sewer smell in your home, there may be a dry trap in the drainage system. Often the smell comes from a seldom-used floor drain in the basement or laundry room. This is the most common source of sewer smells in a home. (See Figure 1: Floor Drain Trap.)

Figure 1: Floor Drain Trap
All drains to a sewer system have a P-shaped trap which is usually filled with water. The trap provides a seal to keep out sewer gas. If a floor drain is rarely used, water evaporates from the trap over time. Eventually the seal is eliminated, allowing sewer gas (and odor) into your house. The solution is easy: pour water into the drain every few months.
This dry trap problem often occurs in a condo where there is an overflow/drain pan for a water heater on an upper level. The drain pan is piped into a drain line but it only receives water if the water heater is on or the temperature and pressure valve on the water heater is leaking. The solution is simple - routinely pour some water down the drain to fill the trap. The drain in the picture has a funnel and a plastic hose to make the job easy. (See Figure 2: Pan Drain at Water Heater.)

Figure 2: Pan Drain at Water Heater

If the trap is okay and the smell is noticeable mainly around a bathroom sink, try flushing a strong cleaner and bleach down the sink's overflow-the small hole(s) inside the bowl near the rim. This area may have an odor because when the sink fills to near overflowing, water is routed through this inner overflow chamber to the drain. Debris can collect inside the inner chamber, causing mold and odor. (See Figure 3: Sink Overflow Odor.)

Figure 3: Sink Overflow Odor
If neither of these measures solves a sewer smell problem, there may be a small leak in one of the vent lines of the plumbing system, or a small leak around the base of a toilet or other fixture. You may need the help of a plumber. Check for loose fittings, corrosion, or holes in vent piping. Also, check the top side of horizontal drain pipes. If the top is rusted, the pipe may never leak liquid but it will leak sewer gas. Drain lines made of copper, steel or cast iron may all exhibit this problem. Corrosion and holes are not visible unless you look on the top of the pipe - often a difficult task. (See Figure 4: Drainage:Waste and Vent [DWV] Detail.)
Figure 4: Drainage: Waste and Vent [DWV] Detail
Sewer Smell from Toilet
When urine and sewer smells persist near a toilet despite careful cleaning, try to identify the source of the smell. Is it from the hot water? Is it from the floor around the toilet? Is it from the sink or tub?
If the smell comes from the area around the toilet, there may be an air leak at the wax ring of the toilet or in the vent pipe. Check to see if the toilet is tightly sealed to the floor. Grab the bowl of the toilet and try to slide it from side to side. It should resist a few pounds of pressure. If the toilet rocks from side to side, the wax ring has failed and is a potential source of a sewer smell. (See Figure 5: Floor Stain at Toilet.)
Figure 5: Floor Stain at Toilet

To replace the wax ring, hire a professional plumber. It's necessary to check the spacing between the pipe flange and the toilet base, and it is difficult to properly secure a toilet and new wax ring in place over the toilet flange.
Smells from the floor area may indicate that the toilet wax ring is leaking, wetting the subfloor: a rotting subfloor and floor covering stinks! If the floor is vinyl, you will notice gray or dark stains in the vinyl that can't be removed. The gray stains are from water leaks around the toilet, under the vinyl.
Sewer Smell from Hot Water
Smells from the hot water may be caused by bacteria in the water heater and reaction with the anode rod in the water heater. Some private well systems have naturally occurring sulfite reducing bacteria in the water table. The bacteria are not harmful to humans but it does create a smell like rotten eggs.
The water heater helps activate the bacteria. The anode rod in the water heater also reacts with the bacteria. You can remove the anode rod to limit the smell but this will void the water heater warrantee. You can also have a professional treat the well and your plumbing system with a disinfectant that will temporarily kill the bacteria. This is often called shocking the well and may need to be repeated on a routine basis.
Smoke Smells from the Fireplace - Without a Fire
A smoky smell coming from a fireplace that's not in use is probably caused by negative pressure that draws air down the chimney, through the stinky flue and ashes into your home. (See Figure 6 Backdrafting Fireplace, Kitchen Fan.)
Figure 6 Backdrafting Fireplace, Kitchen Fan

First, check that the damper is in good condition and is tightly closed. If there are fireplace glass doors, close them. Close any outside air supply to the fire box.

Now think about what may be causing the pressure that draws air down the chimney. Clothes dryers and kitchen exhaust fans are notorious for this. Bathroom fans and other ventilation fans also remove air but a smaller quantity. A whole-house ventilation fan is another likely culprit. A naturally drafted gas appliance like a water heater or furnace also removes air from your home and sends it up a different chimney along with combustion gas. Some high-efficiency furnaces and water heaters have a draft fan that draw air from inside your home. Analyze this problem carefully because the negative pressure could also cause a gas furnace or water heater to backdraft, sending combustion gas into your home. Backdrafting is a serious safety concern. You need to have a heating contractor or an engineer analyze the problem.
You should always check naturally drafted gas appliances for signs of back drafting - condensation on the flue pipe, rust, burn marks around the burner or melted plastic or insulation around the draft diverter. Backdrafting is always a home inspection defect that needs further evaluation. A gas water heater that vents up a chimney is a good example of a naturally drafted gas appliance.
The solution may also be simple if the problem is caused by a tight home. Open a window slightly when running the clothes dryer or kitchen exhaust fan to provide another air source so air won't be drawn down the fireplace chimney.
Fireplace Smells in the Basement
I have been in homes with a fire smell in a basement when a wood burning fireplace is used on the first level. If there is a lack of combustion and draft air for the fireplace, the fireplace creates a negative pressure and causes the gas appliances to backdraft. It can draw air down a water heater chimney. The air flowing down into the draft diverter of the water heater comes from the smoky and smelly air near the top of the chimney, so there is a fireplace smell in the basement. Again, the solution is opening a window near the fireplace and an evaluation by a building scientist.
Smelly Kitchen Sink
Food deposits sitting in a kitchen sink trap or disposal may develop a foul smell. You can clean the trap by pouring a gallon or two of boiling water down the drain and then following with about a half-gallon of vinegar. Allow the vinegar to sit in the trap overnight, and then flush with water. (See Figure 7: Disposal Odor.)
Figure 7 Disposal Odor
If you like the feel and excitement of a little foaming action, add baking soda to the trap before you add the vinegar. It will foam and froth, and some claim this improves the cleaning process. (See Figure 8: Clean Disposal.)
To clean the disposal: run cold water down the drain, turn on the disposal, and run several handfuls of ice cubes down the disposal. The hard chunks of ice will help dislodge food particles. Follow with a lemon rind or orange rind to help remove
deposits and create a clean aroma. You should also clean the rubber flaps at the top of the disposal. The underside of these flaps can be coated with food, another source of a foul smell. Scrub the flaps with a stiff bristle brush and a strong detergent. Flush well after cleaning. (See Figure 8: Clean Disposal.)
Figure 8: Clean Disposal
Tom Feiza has been a professional home inspector since 1992 and has a degree in engineering. Through, he provides high-quality marketing materials that help professional home inspectors boost their business. Copyright © 2017 by Tom Feiza, Mr. Fix-It, Inc. Reproduced with permission.

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