The smell of sewage coming from your air ducts can be alarming, especially as you keep your home as clean as you possibly could. That smell may be coming from your air conditioner, but it may also come from external sources that have traveled through your air handler. Here are the common reasons for that sewer smell in your home.

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What Causes that Sewage Smell Coming from Air Vents?

The most likely reason for that sewer smell is a busted or backed up sewer line. That sewage smell is coming from actual sewage - which is both unpleasant to smell, and dangerous to your health. External factors, dirty filters, and pet wastes are among other causes of sewage smells getting into your home.

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Reason #1 Raw Sewage

The most obvious reason for the sewage smell is raw sewage. You may have a busted sewer vent pipe in your home, which is causing sewer gas to travel up to your air conditioner. A backed up sewer line can accumulate waste, and travel through your air ducts into your home.

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This often happens when the pipe lining has deteriorated over the years, creating cracks or weak points in the pipes that lead to a leak. Contact your plumber for this issue, and consider having your septic tank emptied often to prevent the smell from entering your home.

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Reason #2 Fleeting Smells

Fleeting smells are smells that may seem like they're coming from your air conditioning systems, but are actually from an external source. A burning smell may not come from your air conditioning unit, but exhaust from cars passing by that are causing the burning smell. Same goes for a rotten egg smell, sewer smell, or other AC vent smells.

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If you smell sewer gas from your air duct system, but the smell passes by without lingering, then the smell was most likely from a passing garbage truck, open septic tank, or other external sources that you do not need to worry about. Set your air conditioning unit to filter out odors when possible, which can be done in select aircon models.

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Reason #3 Dirty Filters

Dirty filters would have more of a musty smell from mold growth, but high amounts of nitrogen, methane gas, and hydrogen sulfide gas in the air can accumulate in your damp and dirty filters, causing that sewage odor or rotten eggs smell in your air ducts. Dirty filters collect debris, dust, and dirt that latch onto odors, which may be what is causing your air conditioner to smell like rotten eggs.

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Washing your air filters every two weeks is part of proper air conditioner maintenance, and will prevent any smells coming from your HVAC system. Clean the filter and evaporator coil by vacuuming it to remove the dust, and wash the filter mesh under running water and soap to deep clean it. Let the filter dry before placing it back into your unit.

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Reason #4 Pet Wastes

Have your pets been potty-trained? Even well-behaved pets may have accidents, especially when they have not been let out to do their business. Locate the source of the smell - you might be surprised to find pet waste right next to your air vents! Grab a plastic bag to wrap up the waste, and disinfect the area with a deodorizing sanitizer.

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Alternatively, you may have moved your cat's litter box closer to the vent system, which is what caused the sewage odor coming from the litter box to travel through your air ducts. In this case, simply move the litter box as far away from the HVAC system as possible, and clean the sand every day.

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How to Get Rid of Sewage Smell

Have a Professional Inspect Your Pipes

Contact a professional plumber to inspect and fix the leak in your sewage system. You may have an overflowing septic tank, or a pipe that needs to be replaced. Talk to your plumber about relining or replacing your pipes as needed to get rid of the smell once and for all.

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Chemical Wash Your Air Conditioning Unit

Our chemical wash service overhauls each aircon part, and cleans them with a chemical cleaning solution that will refresh the components. This is especially helpful in removing the lingering smell of sewage from your aircon, and will keep your aircon components from breaking down as well.

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Check for a New Filter

The filter of your cooling system may no longer be effective in keeping smells away from your home. This is what causes those fleeting smells, which are a nuisance as car exhaust, garbage smell, and burning smells get into your home. Consider opting for a new aircon filter that fits the same model and brand of your aircon to keep the smells out.

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Tips to Prevent Air Conditioner Smells

Tip #1 Have Your Home Inspected Regularly

Have your drains, pipes, and sewage systems undergo home inspections at least once a year. Have your septic tank drained, and keep it covered to prevent the smell from escaping into your home. Talk to your plumber about relining the pipes to prevent weak points from leaking. These will keep your home odor-free, healthy, and clean.

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Tip #2 Keep Pet Toilets Away from the Air Vents

Pet toilets are those cat litter boxes and dog potty trays that many homeowners keep in their apartments for their pets to relieve themselves. When these are positioned too close to the warm air vents, the smell can travel through the ductwork. Prevent this by using deodorizing litter sand, and positioning the potty trays as far away from the vents as possible.

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Tip #3 Go for Professional Aircon Cleaning

Our professional aircon cleaning services at Luce Aircon will remove the majority of smells from your cooling system, leaving you with a pleasant, cool feeling from your aircon! Our HVAC technicians are well-experienced with different types of air conditioners, so you can be sure we'll get the job done right.

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Professional deep cleaning is the way to go to prevent aircon smells from your ductwork. Aircon cleaning refreshes the different aircon components, so you don't have to worry about smells sticking to your duct system.

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Check out our article on why ac smells like burning!