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Does Your Plumbing Have Stinky S Traps?

Learn why S traps stink and what to do about it.

Does Your Plumbing Have Stinky S Traps?Have you noticed that some of your sink drains have a bad sewer-like odor? Does the smell seem worse after you drain a full sink of water or when you haven’t used the sink for a long time? The culprit could very well be a stinky S trap.

What is an S Trap?

All types of drains need some kind of “trap” to hold water in the pipe and prevent sewer gasses from traveling up the pipe, out the drain, and into your home. In the case of an S trap, the pipe below the drain has two bends that look just like an S on its side. This type of trap is commonly installed by amateur plumbers, especially when working on fixtures such as a bar sink or basement bathroom sink that is not attached to a vent stack.

Why Does My S Trap Stink?

Because S traps are not vented, there is the potential for the water that is supposed to remain in the trap to get siphoned out as the fixture drains. This is especially likely to happen if you are trying to drain a full sink as there will be more pressure on the pipe. If you hear a bunch of gurgling as the very last bit of water drains away, this is typically a dead giveaway that the water in your trap is being sucked away.

Another possible problem is that the water in the S trap may simply have evaporated due to a long period of disuse. You could actually have this problem with any trap, not just an S trap.

What Can I Do About the Stink?

The simplest way to deal with a stinky S trap is to just run a bit of water down the pipe to refill the empty trap. You would need to do this every time you drain a full sink, as well as a few times a month in the case of a drain that doesn’t get used too often.

However, for a more permanent solution you really should replace the S trap with a properly vented one. Depending on how the plumbing around the fixture is set up, this may be as simple as installing a P trap to replace the S trap. In other cases more extensive work such as adding a vent stack may be required.

If you need help with stinky, slow, or unvented drains, an experienced plumbing contractor like US Comfort can help. Call 800-738-4160 to reach us.

Posted on November 18, 2015