A drain trap is the part of the pipe that remains full of water in order to prevent sewer gases from entering the home. The water in the trap acts as a barrier that prevents the sewer gases from traveling back through the pipe, up through the drain, and into the home. All of the plumbing fixtures in your home should have a trap on the drain line to prevent sewer gases from entering your house.
What’s the Issue: S Traps are common in older homes but are no longer authorized in newer homes. You can easily determine if you have a S Trap because it resembles the shape of a sideways letter “S”. The shape of the trap is known to cause the water in the trap to siphon leaving no water left in the drain which allows sewer gases to enter the home.
Do I have to Improve it: If you don’t smell sewer gases than the trap is working properly and you do not have to replace it, when you sell your home you can bet that the home inspector will note it as a defect and you might end up upgrading to a P-Trap regardless.
How to Improve It: If you are experienced in home repairs there are several YouTube videos that show how to convert a S Trap to a P Trap but I recommend allowing your local plumber to make these repairs for you.