A toilet that still smells after cleaning often has a problem you cannot reach with a brush. The most common causes are a failed wax seal under the toilet, buildup hidden under the rim, a low water level in the bowl, or a plumbing vent problem.
A Failed Wax Seal
The wax ring under the toilet seals it to the drain pipe. If the seal breaks, sewer gas and small amounts of water can escape around the base. Signs include a smell strongest near the floor, a toilet that rocks, or staining around the base. Water may seep into the floor after each flush.
Hidden Buildup
Bacteria and minerals can build up under the rim and inside the small holes that send water into the bowl. These areas are hard to see and clean. A small mirror can help you look under the rim. The area around the bolts at the base and behind the toilet can also collect odors.
Low Water in the Bowl
The water in the bowl acts as a barrier against sewer gas. If the level drops too low, odors can rise from the drain. A partial clog, a crack, or a blocked vent can pull water out of the bowl. A toilet that is rarely used can also lose water to evaporation.
Vent and Drain Issues
Plumbing vents carry sewer gas out through the roof. If a vent is blocked or cracked, gas may escape into the bathroom. Gurgling when other drains are used is often a sign of a vent problem. A cracked drain pipe under the floor can also release odors. Checking the vent on the roof should be left to a professional.
If cleaning does not fix the smell, the problem is likely in the seal or drain. Lifting the toilet and replacing the seal often solves a smell at the base. For odors that spread beyond one bathroom, you can have a plumber look at the venting and drains at (833) 603-1840.