Is Back-Drafting Causing Sewer Gas Odors in your home or office?

What’s that sewer smell?

If you are smelling an odor akin to the sewer in your home or office, it’s likely that back-drafting is happening. Back-drafting refers to conditions which create sufficient negative air pressure inside a building such that gases may be sucked into the building from a plumbing drain system or such that heating appliances may lack adequate combustion air and possibly allow carbon monoxide to build up enough to induce suffocation. The latter is particularly dangerous as carbon monoxide has no smell.

Right now Houston is experiencing some intermittent stormy days.  This being Houston, we do know that in the future we will get bouts of very heavy rain and flooding, even tropical storms.  Indoor sewer gas odors can occur from a combination of wet weather, flooding sewer and storm drains, and back-drafting in the home or commercial building due to improper exhaust fan vent installation.  Back-drafting in a building causes more than bad smells.  It can lead to the intake of explosive methane gasses from the sewer system or potentially fatal carbon monoxide hazards from heating appliances in the building.

Any of several factors listed below can cause negative air pressure inside a home or commercial building  such that back-drafting may occur at the plumbing vents or building drains

  • Rain, wet weather, and local flooding can allow sewer gases to back up through building drains. The gasses can correctly move up through building vent piping to the roof, or incorrectly move into your home or commercial building through the dry traps and drains.
  • Sewer gas reentry into homes or buildings: When a plumbing vent is incorrectly located too close to a door, window, soffit vent, or even a kitchen or bath vent duct, vented sewer gasses can come back into your house or commercial structure. The reentry of vented sewer gases is more likely when:
    • Strong steady wind pushes sewer gases from a source towards any building openings, windows, vents or doors
    • Other conditions (heavy rain, storm drain flooding, or sewer drain flooding) produce higher than typical levels of sewer gases venting through a structure’s plumbing vent system
  • Kitchen exhaust or Bathroom fans produce negative air pressure in their respective rooms to draw out cooking or unpleasant bathroom odors.
  • Doors left open between the basement and the upper building areas can provide a path for air (and odors) to pass to upper building levels.
  • Tight building construction, a desirable practice that minimizes leaks and thus saving on building cooling or heating costs, will reduce the prompt supply of new outdoor air when any other  condition is resulting in air movement out of the home or commercial building. Without prompt entry of new outdoor air in a tightly sealed building, back-drafting safety margins decrease making plumbing mistakes all the more dangerous.
  • Exhaust-only ventilation systems in buildings can produce back-drafting conditions, especially in tightly sealed buildings.
  • Homes with large ventilation exhaust fans produce very powerful negative indoor air pressure which is sufficient to create back-drafting that affects both the plumbing system drain and the plumbing vent piping and possibly the heating or cooking appliances.
  • Windows opened on upper building floors and closed on lower building floors increase air movement upwards in these buildings.
  • Fireplaces, while being used, especially open fireplaces that don’t have an air-tight glass fire screen or door, can create significant air movement out of the building and then up the chimney, potentially causing back-drafting in other building areas.
  • Warm air in a commercial multi-story building rising by natural convection during cold weather creates negative air pressure on lower floors, drawing sewer gases out of the dry traps, drains, or any faulty plumbing vent piping.

If you are smelling a sewer odor now or if you have smelled a sewer odor in your home or commercial building during a storm or rainy day, you have a potentially dangerous plumbing issue that you are not aware of. Don’t ignore it! Give us a call at Nick’s Plumbing and Sewer Services so we can check it out for you. Remember, we are the guys that fix the problems your plumber created.

Nicks Plumbing and Sewer Services fixes the problems your plumber created

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