Is There A Septic Smell In the House? (Find Out Why)

One of the worst things to come home to is a septic, or sewage, smell emanating from inside your house. Your first thought might be the garbage didn’t get thrown out or a dead rodent is inside your walls. Depending on where the smell is coming from, it could be from either issue, both, or neither one at all.

A septic smell in the house is most likely caused by a simple plumbing issue, the shower drain, or washing machine. Bacteria from the water heater may also be the culprit and contribute to noxious odors permeating the home. But, the smell could be thanks to problems with the septic tank itself; your first step is diagnosing the source.

A septic smell in your house does not necessarily mean that your septic tank needs pumping. More often than not, you may more likely be dealing with a simple plumbing issue. Here are a few places to check should you encounter a septic smell in your house.

Unused sinks may also be to blame when the sink P-trap dries up. In fact, you should check any water fixture with a P-trap, not just the sink. When a sink or toilet is unused, the trapped water evaporates and septic smells come in.

A P-trap is the u-shaped part of the pipe under the drain and keeps sewer smells from coming into the home. This design not only allows wastewater out but also “traps” water in, acting as a plug for sewer smells. Drain lines directly access the sewer system, and water in the pipes keeps the sewer smell out.

That washing machine keeping clothes clean and smelling great may be suspect in making your home smell like a sewer. For one, it may have an improperly installed P-trap allowing sewer smells to seep through. Check to see that the washing machine hose is not inserted too far into the drainage box.

Another possible cause would be a clog in the washing machine drain pipe or hose. As with the shower, there may be a build-up of biological materials such as hair, skin, or even detergent. A plumbing snake or long tool will have to be utilized to dislodge the material buildup from the hose.

Believe it or not, cold weather can bring out funky smells. One reason could be that your septic system basically freezes when temperatures drop too low for its comfort. You may also have a vent stack blocked by snow that forces septic gases back into your house.

Downdrafts in the winter may also result in septic gases blowing back in the house through your air conditioning unit. Wind velocities are also notoriously low in cold weather, which equals stale, unmoving air.

Water heaters are susceptible to bacteria colonies and may produce a noxious smell that permeates the house. These bacteria produce hydrogen sulfide gas as they interact with the magnesium in your tank’s sacrificial anode rod. Hydrogen sulfide causes that sulfuric or rotten egg smell.

These bacteria can survive in the hot water tank without oxygen. You may need to contact a plumber to flush out and disinfect your tank. If there’s a corroded anode rod, you may need to replace it, preventing bad smells in the future.

Despite its proximity, you should never be able to smell your septic tank, even if you’re standing directly over it. A human nose should not detect the gases emitting from a septic tank. This is because there should always be a properly fitted and tightly shut septic tank seal.

If you do detect these toxic gases coming from your septic tank, ensure the risers and manholes are securely covered. If the seals look secure, check that the tank is not full and is not due for pumping.

Some homeowners realize that even after pumping their tank, the odors don’t go away. In this case, adding biological additives to the tank may be required in solving this smelly problem. Maintaining the PH level around 6.8 to 7.6 will prevent hydrogen sulfide from being present in the tank.

This possible cause only applies to you if your house is not connected to the municipal wastewater management system. Before you find the drain field, you need to locate your septic tank first. Look for a cement marker that is about the size of a manhole cover about 10-20 feet away from your house.

Once you locate your septic tank, you should find the drain field on a downward-sloped path or field. The drain field is made up of a network of pipes in gravel-filled ditches. If the septic smells come from your tank or your drain field, there will be no mistaking it.

Repairing a damaged drain field or septic tank requires the expertise of professional and insured contractors. You may want to try adding a biological solution first and see if this takes care of the problem. But if there is actual physical damage on the tank or field, then a replacement or new structure is necessary.

Related Questions

Can I pump out my septic tank myself?

If you are a certified septic engineer with the proper tools and equipment, then, yes, you may.  Otherwise, this task is best relegated to the professionals. After pumping a septic tank, the material waste is considered hazardous waste and must go to a sanitary treatment plant.  

The sewer smell is in my sink; what should I do?

Pour a fourth of a cup of baking soda down the drain, followed by a cup of white vinegar.  Let sit for 2 hours with the bathroom door closed, then pour a gallon of hot water down the drain.After 15 minutes, run cold water down the drain for 10 minutes to rinse the vinegar down.  

How do I know if toxic gases have poisoned me?

If you find yourself in an environment with noxious smells, be aware of exposure to gas poisoning.  The most common symptoms to look out for are headache, dizziness, vomiting, chest pain, upset stomach, and confusion.  Gas poisoning symptoms have also been described as “flu-like.” If you feel any of these effects, leave the area and seek medical attention immediately.