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Why Does My Toilet Smell Bad?

A toilet affixed to a wood tiled wall with a small metal trashcan and a toilet paper holder to the right of it and with a black and white tiled floor underneath it with a bright blue rug in front of it.

Few things are as unpleasant as the smell of sewage, especially in an enclosed area like a bathroom. Have you ever wandered into your bathroom only to immediately block your nose and ask, “Why does my toilet smell bad?” You’ve run into one of the most common toilet issues: a lingering foul odor.

You’ve tried deep cleaning it, but the smell continues to linger. A persistent toilet stench can come from several different issues, including:

In this blog, we’ll cover how you can resolve the overwhelming odor and when you need to call a professional plumber to identify and remedy the problem.

Want an expert plumber’s help with a toilet issue?

Trust the experts at Advantage Air Mechanical, and rest easy knowing that your foul toilet odor will soon be a thing of the past. We’ve helped hundreds of homeowners solve their plumbing troubles in the Tucson, AZ area for over 30 years. Book with us today; we offer convenient 2-hour scheduling windows.

Call us today at (520) 792-9400 or schedule below to experience 5-star plumbing service!

Evaporated Water

A person pressing the flush button on top of a white toilet, in a marble tiled bathroom.

One of the most straightforward toilet odor problems to address is a lack of water in your toilet’s p-trap, a curved pipe behind your toilet that forms a “p” shape. It traps liquid to block unwanted gases from returning through the pipes. Without enough water in the p-trap, nothing stops the sewer gas smell from escaping.

This can also happen when you don’t flush a toilet often enough, either because it’s a rarely used bathroom or because you went on vacation.

In most cases, you probably don’t even need to call a plumber to fix this one. Just flush your toilet a few times and let the p-trap fill up with water. If this doesn’t seem to eliminate the odor, there could be another hidden problem.

Clogged Toilet Drain

Most people think that a toilet clog prevents it from flushing. However, you could have a clog somewhere deep in a plumbing pipe, and you would never notice because the toilet still flushes. A deep pipe clog might be responsible for your toilet smelling bad but otherwise working like normal.

Clogs usually develop because something got flushed down the pipes that shouldn't have. Items that cause clogs include cotton swabs, feminine hygiene products, dental floss, tissues, wet wipes, condoms, and excess toilet paper. Even if a product says it is safe to flush, it can still clog or damage your pipes. Contact a plumber to have your drains cleaned.

Check the Water Level

If you’re sure that the clog isn’t the result of something being flushed that shouldn't have, check the toilet tank’s water level and flapper. Toilets need a lot of water to flush waste properly. When the water level in the tank is too low, the toilet can clog. To see if this is the cause:

  • Lift and remove the tank lid.
  • Find the mark on the inside of the tank that indicates where the water level should be.
  • Adjust the float, an object that “floats” upward as the water rises in the tank, until the water level matches the mark. Some floats have arms that require lifting, while others use a float adjustment screw on top of the fill valve.

Secure the Flapper

A man wearing a plaid long sleeve shirt is kneeling down next to a toilet with it's tank lid off, showing the pump and inside of tank.

A toilet tank that seems to be leaking water or refilling nonstop—even without you flushing it—can indicate a problem with the flapper. Whenever you flush the toilet, a chain should lift the flapper and allow water to drain from the tank. This flapper is a small rubber seal covering the hole at the bottom of the tank. At all other times, the flapper stops water from escaping.

A flapper chain that is too short will allow water to leak slowly from the tank, leading to weaker flushes and increasing the risk of clogs. Adjust the chain by removing it and hooking it to a hole closer to the toilet handle. When you flush the toilet, the chain should have just enough slack to open the flapper fully.

The flapper itself may also be the source of the issue. Old, worn out, or otherwise damaged flappers may fail to form a perfect seal and require replacing.

Bacteria Buildup

As you might expect, sewage contains a lot of bacteria. Occasionally, bacteria can travel from the pipes to your toilet bowl. While fresh toilet water and routine cleanings can help, hot and humid weather creates the perfect conditions for bacteria to multiply rapidly. Bacterial buildup can produce a foul smell, resembling sewage or rotten eggs.

If microorganisms grow in the toilet bowl:

  1. Pour a cup of heavily diluted bleach into the overflow pipe or flush valve.
  2. Wait about 30 minutes.
  3. Flush the toilet a few times.

To eliminate bacteria in the toilet tank:

  1. Drain the water and use a brush to scrub the walls with heavily diluted bleach.
  2. Wait about 10 minutes.
  3. Carefully wipe the walls and refill the tank.
  4. Flush the toilet several times.

While cleaning the toilet, remember to scrub under the bowl’s rim or the various crannies behind it. Be careful about using other chemicals or powerful bleach solutions, as they can easily damage your toilet and pipes. Bacteria accumulating in other parts of your toilet, such as the supply pipes, requires professional attention.

Vent Pipe Issues

Your toilet’s vent pipe is one of the most important parts of your home’s plumbing system. It also happens to be one of the most overlooked. When working properly, the vent pipe dissipates wastewater gases and toilet odors into the outside air. Clogs in the vent pipe cause gases to back up and eventually escape into your bathroom.

These vent pipe clogs can be due to leaves and other natural debris. Animals are also common culprits. Because of the potential for damage, a professional plumber is the best choice for resolving vent pipe issues.

Broken Sealing Ring

Just beneath your toilet is a ring that acts as a seal. It helps keep the toilet in place while stopping gas and water from escaping. Over time, these sealing rings can develop natural wear and tear or get loose, letting foul odors from the sewer line below the toilet escape.

Contact a professional to replace the sealing ring. Experts have the tools, know-how, and experience necessary to fix sealing ring issues quickly, safely, and correctly. They can also advise you on whether a traditional wax ring or a waxless option is the best route for your toilet and budget.


Get Trustworthy Toilet Repairs from Advantage Air Mechanical

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When you run into toilet issues and need professional plumbing help, contact Advantage Air Mechanical. Our plumbers are some of the best in the Tucson, AZ area. With over 30 years of experience, we back up our work with upfront pricing and labor warranties. We don’t pay team members commission, so we’ll never upsell you during a toilet repair. We’ll do the job correctly the first time, satisfaction guaranteed.

Call us at (520) 792-9400 or click below to schedule online today.