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Do Shower Drains Need a Trap?

Steven Symes

A trap piece in your shower’s drainpipe performs a very necessary function in your house’s plumbing. Failure to put a trap in your shower’s drainpipe may lead to serious consequences, including death.

Traps in a shower's drain line help keep sewer gases from entering your house.

Contact your local government for details on what type of trap is required for your shower’s drain by local building codes.


All of the plumbing fixtures in your house need to be connected to a vent pipe, which helps manage the sewer gases in the drainpipes. The sewer gases come up from the sewer and travel up the drainpipes. The vent pipes connect to the larger drainpipes in your house, giving the sewer gases an escape route out of your house. The vent pipes run all the way up through your house’s roof, where they open up in the fresh air.

Trap Function

While vent pipes help keep sewer gases out of your house, they alone cannot perform the work. A trap must be present in each drain line connected to the various plumbing fixtures in your house. If you look underneath your sinks you will notice the curving trap pieces in the pipes. At the bottom of a toilet, from the side, you can see the curving section of the drain line. The trap literally traps water in it because of its curving shape. The water in the trap stands in the way of sewer gases that do not at first go up the vent pipe, keeping them from progressing any further up the drainpipe. Without the trap in place, at least some sewer gases would make it through the shower drain and into your bathroom.

Sewer Gas Health Risks

Sewer gases smell horrible, but they also present health risks. Sewer gases may contain toxic elements, which may lead a person to feel lightheaded, nauseous or drowsy. Exposure to sewer gases may also cause people to faint or asphyxiate. If your bathroom has less than 12 percent concentration of oxygen, exposure to sewer gases may lead a person to fall unconscious and die without any warning signs, according to the Wisconsin Department of Health Services.

Sewer Gas Explosion Risks

In addition to containing some toxic gases, sewer gases may also contain methane and hydrogen sulfide. These gases both are highly combustible, meaning they could ignite if they come into contact with an open flame in your house, such as a pilot light, or even from contacting a spark from turning on a light switch. Once the sewer gases ignite, they may lead to a fire or explosion in your house.