Floor drain smells bad from dry trap use bleach

Floor drain smells could be from a dry floor drain trap. Water in the trap prevents sewer gas from escaping from the drain line. The drain smells because the water evaporates from the trap and sewer gas will vent into the house. The amount of gas expended into the house will vary by sewer and wind pressure.

The foul odor seems to come and go. When it is noticeable, it smells like a dead musty animal. You won't any leaks in the plumbing.

Typically air pressure from the sewer escapes harmlessly through the vents on the roof. If a drain trap dries up, it will allow gas to pass directly into the home.

To refill the trap all you need is water but I prefer to add household bleach to my water. Add two cups of household bleach in one gallon of water and dump the contents into the drain. If there are any other unused sinks, showers, or toilets in the basement give them the same treatment.