Sewer Gas Smell in Basement (What Causes It & How To Eliminate)

Is there a sewer smell in your basement? A sewer smell that smells like gas, is horrible, and it can be dangerous for your household. This sewer smell is hydrogen sulfide from the gas and it almost always points to a bigger problem with the sewer system. When you notice signs of sewer gas in your basement, you need to address it immediately.

Clogged pipes are one of the most common reasons basements smell like sewer gas. This happens because the clog is usually located in one of the pipe’s vents. There is no way for the sewer to ventilate the air, leading to a foul smell inside your home. You can fix this problem by cleaning out the drain.

We’ve spoken with the experts to get the best solutions to eliminate that awful sewer gas smell from your basement. In order to make sure you apply the right solution, you need to know what’s causing the smell. Let’s go over the most common causes, starting with the easiest to check.

Common Causes Of Sewer Smell In Basement

1. A Water Trap Has Dried Up

Every water appliance has a water trap (i.e. toilet trap) where it’s connected to the pipe system. The water trap prevents odors, bacteria, and other things that shouldn’t be in clean water from traveling into your water appliances. It plays a big role in making sure your water is clean and odorless.

However, the water trap needs to have water in it. If it dries up, it will no longer serve its purpose. That’s why you will begin to smell a foul sewer smell.

It’s more common for water traps of appliances that don’t get used often to have this foul smell. If there are basement floor drains in your house that don’t get used on a regular basis, it could be the culprit. However, if the foul sewer smell is in the basement, it could be coming from a sump pump that is not working or has been inactive.

Keeping the water trap clean is the best way to prevent this sewer smell from coming back. Pouring hot water down the drain with the dried-up water trap is a great way to eliminate the smell.

What you need: rubber gloves, soft-bristle cleaning brush, rag, water, white vinegar or cleaning agent

How To Clean The Water Trap

  1. Put on the rubber gloves. Dilute a small amount of vinegar or cleaning agent with water.
  2. Locate the water trap that doesn’t get used regularly.
  3. Remove the cap from the water trap. However, leave the rest of the trap in place. You can remove the cap by hand.
  4. Dip the soft-bristle brush in the cleaning water. Thoroughly scrub the cap. Dip the brush in the cleaning mixture again, and light scrub inside the water trap.
  5. Use a rag to dry off the cap and around the water trap.
  6. Fasten the cap back onto the water trap.
  7. Pour hot water down the drain.

2. You Have A Bad Toilet Wax Ring

Every toilet has a wax ring seal. The wax ring seal provides a seal between the toilet and the sewer pipes. This wax ring can crumble or tear if the toilet is older or poor-quality sealant was used. It can also become damaged if the toilet wasn’t installed properly.

The point of this seal is to keep odors, water, and other unwanted hazards out. Once the wax ring seal breaks, it won’t be long until the sewage gas starts seeping in. When you have a bad wax ring, the toilet may feel loose or you’ll notice water on the floor below the toilet.

How To Replace A Wax Ring

3. You Have A Clogged Pipe

The issue that plumbers run into the most with sewage gas in the basement is clogged pipes. In most situations, this bad sewer smell is coming from the large drain in the basement. It’s very likely that the drain line that it’s connected to is clogged.

There is also a chance that you’re smelling this odor because one of the pipe vents is clogged. This sewage smell will appear because there isn’t a way for the sewer air to be ventilated causing poor air circulation. You could temporarily open the vent cap on the roof to increase air circulation.

You will likely notice other signs if there is a clogged pipe, such as:

  • Slow draining
  • Gurgling sounds
  • Drain backing up
  • Lower water levels in the toilet

Unclog Drains Or Pipes

You can unclog any drain or pipe in your house when you have a problem. Once you have figured out which drain is clogged, there are a few ways you can clear it.

Never use a heavy-duty drain cleaner when you’re dealing with a clog. The chemicals can do damage to your pipes. If the clog is too complicated and requires a plumber, the sitting cleaner can be hazardous.

Here is a safer way to approach a clogged drain.

What you need: hot water, baking soda, vinegar, plumber’s snake

  1. Pour hot water down the affected drain. Make sure the water is hot, but not boiling.
  2. Add 1 cup baking soda, 1 hot water, and 1 cup vinegar to the drain.
  3. Quickly cover the drain with a plug, rag, or other objects to stop the pressure from releasing. Make sure you keep the drain covered for 5 to 10 minutes.
  4. Pour hot water down the drain.
  5. If the clog is still there, you will need to use a plumber’s snake. Release the clasp on the snake that is keeping it closed. Position the snake into the drain and slowly release it until you meet an area where you feel resistance.
  6. Apply a small amount of pressure and rotate the snake. Continue doing this until the resistance is no longer there.
  7. Pour hot water down the drain again to prevent the obstruction from occurring elsewhere in the pipes.

4. Damaged Sewer Line

Unfortunately, not every sewer problem is as easy to detect as the ones we mentioned above. A damaged sewer line can also allow sewer gas to seep into your basement. It can also lead to mold growth throughout your house and create an opening for rodent infestations.

So, how do you tell if this is the problem? There are a few other signs that will point you toward a damaged sewer line.

  • Slow drainage that you can’t fix by clearing the drains
  • Moist lawn
  • Mildew and mold formation
  • Rodent infestations when you previously never had a problem

You may be able to repair a sewer line at home with the right products. However, this will depend on where the crack is located and how bad the damage is. You will need to contact a professional plumber if the crack is too far down in the sewer system to reach.

The problem can be addressed DIY if the crack isn’t excessive and it’s in an area that you can get to. Here is what you need to do.

What you need: wrench, plumber’s tape or silicone tape, flashlight, dry rag

Please note: this solution is for low-pressure pipes. You will need to contact a professional for areas in the piping system that experience high pressure.

  1. Locate the area where the crack is. Double-check that everything is secured in place. Often homeowners believe there is a crack when the problem is really a loose coupling nut. Make sure all the nuts are fastened tightly and test the water to see if it still leaks.
  2. If it still leaks the problem is a crack. Use a flashlight to locate where the crack is. When you spot the crack, use the rag to dry it off.
  3. Wrap the affected area with plumber’s or silicone tape. This will temporarily fix the problem until you can replace the pipe.

5. You’re Missing A Cleanout Plug

Your plumbing system has a plumbing pipe (aka cleanout pipe) that runs all of the wastewater out of the house. A cleanout plug is placed on this pipe to prevent sewage gas and other unwanted contaminants from coming in contact with the incoming water.

If you’re missing this plug or it has become damaged, there will be an opening that sewage gas can get into. This will cause the odor to become prevalent in your basement.

In order to detect if this is the problem, you will need to know where the cleanout plug is located. It could be in your basement or outdoors. Most homeowners can find the cleanout plug by following the main sewer line. The plug will be connected to a “T” or “Y” shape pipe and it will be above ground.

Once you locate the damaged cleanout plug, you can replace it. Make sure you measure the plug to buy the right size of replacement cap. Let’s take a look at what you need to do.

How Much Does it Cost To Address Smell In The Basement?

Addressing the smell could cost anywhere from a few dollars to thousands of dollars. The cost highly depends on what you need to do to fix it. Cleaning the water trap involves vinegar, which costs an average of $2. However, sewer pipe repair or replacements could run as high as $8,000.

Let’s take a look at some of the average costs you could run into.

PartAverage Cost
wax ring seal$200 to $250
Replacement cleanout plug$3 to $55
Plumber’s taper$8 to $25
Plumber’s snake$100 to $275

Once you factor in the cost of replacement items you will need to decide if you want to fix the problem DIY or hire a professional. For DIY jobs, you only need to cover the cost of materials. With plumbers, you will need to factor in the cost of labor. This usually works out to around $100 per hour.

Consult a Professional

Sewer gas is not something you should take lightly. If you’re not 100% sure about how to address the problem, always contact a professional. Plumbing repairs can be complicated and require heavy-duty equipment that isn’t available to most homeowners.

You should consult a professional for clogs you can’t clear out, major damages, and complicated fixes. Sewage gas is a hazard to your health and safety, which is why you shouldn’t attempt to work around it if you’re not confident in what you’re doing.

More times than not, it can be beneficial to hire a plumber. This is because they are familiar with the problem and the correct procedure to fix it. They will also be able to inspect the plumbing system for other signs of problems.

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