Sewer Gas Odor at a Front Entrance

Moisture Problems

• Before attempting to troubleshoot your drain and sewer lines, check to see if it is possible the sewer gas smell is a moisture issue in your crawlspace or basement. A damp crawlspace can create an odor that is not dissimilar from the foul odor of sewer gas. Check the area around your front entrance for vents from your basement or crawlspace, then check under your house for signs of accumulated water or moisture. Improving the ventilation in your crawlspace or running a dehumidifier in your basement may go a long way toward solving your sewer gas odor.

Dry Kitchen Sink Trap

• If your front entrance is located near your kitchen, you may have an issue with your sink drain's trap. A trap is an S-shaped piece of pipe installed between the sink and the drain line. The shape of the pipe is designed to remain filled with water, sealing off sewer gas and preventing odorous and potentially dangerous sewer gas from backing up into your home. If your kitchen sink has not been run for a long period of time, it is possible your trap has run dry. If this is the case, running the sink for a few minutes will refill the trap and solve your problem.

Drain Vent Issues

• All residential drains must be vented to the outside. Drain vents allow air to move freely in the drain and sewer line, which prevents vacuums from forming and keeps waste moving through the system. Drain vents are small-diameter pieces of metal pipe, typically located on the roof. If the drain vent pipe is located near your front entrance, you may have found the source of the sewer smell. Check the drain vent for signs of damage or clogs before further investing time and money investigating your drain and sewer lines.

Leaking Drain Line

• The drain line is the section of sewer pipe located within your home, either in the crawlspace or in the basement. Leaks located on the top of these drain lines can leak sewer gas and odors, but not leak water, and thus may go undetected for a long period of time. Check drain lines for signs of cracks, splits, and leaking water. Replace any damaged or cracked sections of pipe.