How The Type Of Trap On Your Drain Determines How Likely It Is To Clog

2 May 2016
 Categories: , Articles


When soliciting advice from your plumber on how to avoid those annoying recurring drain clogs, you're sure to hear the usual tips about keeping grease out of the sinks and watching what you flush down the toilet. However, it might be part of the plumbing connecting to the drain that is actually causing your clog issues to return again and again. Find out why some types of drain traps are known for creating clog issues due to their design.

The Purpose of Drain Traps

All drains need a trap, or need to be connected to a shared trap downstream, to prevent sewer gas from rising back up the pipes and entering the home. Traps are bends in the plumbing that keep a little water in place to form a barrier against rising gases. Traps are necessary for a safe and healthy sewage system, but some designs work better than others when it comes to allowing clog-causing waste like soap and hair to flow smoothly through the trap. New construction is likely to only feature the reliable P-trap, but older homes often feature more troublesome models.

P-Traps are Reliable

P-traps are the current standard for plumbing, whether you're adding a trap under a toilet or a simple hand washing sink. These traps are named after the shape they make when viewed from the side, with the outgoing sewage pipe forming the long stem of the capital letter P. The dip in the middle of an otherwise smoothly sloped pipe provides the perfect place to trap a little water to control gas flow. P-traps are not known for causing clogs on their own, and they're easy to open and clean out if a wad of hair or grease does end up stuck in that section of the pipe.

S-Traps Clear Too Well

S-traps are the second most common type of residential plumbing trap, and they create issues of their own that aren't clog related. In fact, S-traps tend to clear so well and so quickly that they fail to hold water rather than keeping solid material stuck in place to create a clog. Even if you're experiencing venting and gas problems due to having this kind of trap, it's very unlikely that your drain clogs are being caused by this particular part of your plumbing system.

Drum Traps are Trouble

Drum traps are not very common in newer homes, but they were widely used a few decades ago because manufacturers intended to create a model that was easier to detach for retrieving items dropped down a drain, such as wedding rings and keys. Unfortunately, the cylinder shape of a drum trap causes clogs to form because solid waste doesn't flush out of the trap with each new flow of water. P and S-traps are considered self-scouring, while drums are missing this essential feature. Aside from clog issues, drum traps are also banned in many areas for other problems like the following:

  • Tight installation clearances that make it impossible to actually clean the trap without cutting open your floor
  • Rusted or thread stripped caps that don't come off properly when the trap needs cleaning
  • Water leaks, since the various caps and openings on a drum trap can all let moisture seep out.

Bell Traps are Bad

The final type of residential plumbing trap is known as the bell trap for its unique circular shape. This design was primarily used for floor drains in the past, but it's rarely found on sinks and tubs too. The inside of the trap consists of a curved bell-like shield maintaining a water cap over the vertical drain pipe, but that curved shield also catches debris as it flows by to create serious and persistent clogs.

For more information and advice on updating your plumbing traps, talk with a professional plumbing service near you, such as A Absolute Plumbing & Heating.