In plumbing terms, a “trap” is a curved piece of tubing that will always hold a little water to keep sewer gases from coming through into the house. They are wonderful things. However there is one trap that should be avoided: the S-Trap.
With an S-Trap, the piping turns up, but then goes back down again. I had to address this issue at a project this week where a home inspector found an S-trap in use under the sink. The problem with these traps is that, because of the shape, the water that’s supposed to be blocking the dreaded sewer gases can get siphoned out.
Can you see the S-Trap in this picture?
Even though plumbing codes prohibit them, they are still sold at home stores and found in homes everywhere.
The fix involves adding a P-Trap and a Studor vent.
A Studor vent is a small device that attaches to the drain pipe and will allow some air in and allow venting, but will not allow sewer stink out. They are often used whenever there’s a sink in a kitchen island, or anytime that it’s difficult to vent something. There are limitations to their use, so read the directions before trying it at your project.
Our drain had other issues as well that required replacing the 1 1/2″ line through the floor to the crawlspace. This actually made it easier because now there weren’t any of the old pipes left to deal with.
The new P-trap comes from the sink drain lines and enters my new pipe through a “T”. Above the “T” is the Studor vent. It all goes together quickly once you have the right pieces…
-Peter
