Why Does Sewage Smell Come up Through Floor Drains?

Floor drains have a built-in trap that holds water. This water acts as a barrier against sewer gases. When the drain goes unused for a while, the water evaporates, especially in warm or dry indoor air. Once the trap is empty, gases from the sewer line can move up through the drain and into your living space.

In a humid climate like Virginia Beach, evaporation still happens, especially if the drain is in a rarely used area such as a garage or a utility room. You can test this by pouring a bucket of water down the drain. If the smell fades after that, the trap was dry. If it returns, look for other causes.

• Pour water down the drain once a week to keep the trap filled
• Use a trap seal primer if the drain is rarely used
• Check for cracks in the drain body that let water leak out
• Look for a missing or damaged trap, which allows gas to flow freely

When the main sewer line or a branch line gets clogged, waste and water back up. That backup creates pressure, forcing sewer gases up through floor drains. A partial clog may not cause a visible overflow but can still allow gas to seep out. The smell might come and go depending on water use in other parts of the home.

A blocked sewer line is a serious problem. If you notice multiple drains smelling or slow draining throughout the house, the issue is likely in the main line. In that case, you may need professional help to clear the line. This type of work often involves specialized equipment that only a plumber or water damage pro has.

Start by pouring water down the drain to see if the smell stops. If it does, make it a habit to run water through every floor drain in your home each month. Also, check that the drain cover is secure and not letting air pass around it. A loose cover can let gases escape even if the trap is full.

If the smell persists, the problem may be deeper in the plumbing. You can try cleaning the drain with a baking soda and vinegar mix, but that only helps with surface odors. For persistent issues, consider having a local water damage pro inspect the drain system. They can identify the source and recommend the right fix, whether it is a simple trap replacement or a more involved repair.