Roaches Coming Up the Drain? Here's Why, and How to Stop It

Big roaches coming up the drain in a South Florida bathroom almost always came from the drain line itself, through a trap that dried out or a gap around the pipe. That's why it happens most in the guest shower nobody uses, the tub in a condo that sat empty all summer, or the floor drain in the laundry room. Run water in every drain you don't use often, keep the covers and stoppers in place, and get the gaps around the pipes sealed. If they keep showing up, or the roaches you're seeing near the drain are small, it's time for an inspection.

Why roaches keep coming up the drain

Every drain has a curved section of pipe under it, the trap, that holds a little water. That water is a seal. It keeps sewer air, and anything living in the line, on the other side. When a drain goes unused for a few weeks, the water evaporates, and in South Florida heat it doesn't take long. Now the drain is an open door.

A few situations make it more likely:

• Guest baths and seasonal homes. Nobody runs the water, so the traps dry out.
• Floor drains. Laundry rooms, garages and some older bathrooms have them, and almost nobody pours water into a floor drain on purpose.
• Gaps around the pipes. Under the sink, behind the toilet, where the tub spout comes out of the wall. Roaches don't always come up the pipe. Sometimes they come alongside it.
• Heavy rain. After a big storm, roaches living in the drain and sewer lines can be pushed up toward the house. That's why a lot of people see one the morning after a downpour. Our Fort Lauderdale roach control page talks about rain and drains in older buildings.

Big roach or small roach? It changes the answer

Big, reddish-brown roaches, an inch and a half or more, are usually American cockroaches, the ones everybody here calls palmetto bugs. They live outdoors and in drain and sewer lines, and they come in from there. One after a storm isn't always an infestation. Our post on finding one palmetto bug covers how to tell a stray from a problem.

Small, light-brown roaches near the sink or tub are a different story. Those are usually German roaches, and they're breeding inside the home, not coming up from below. Running the water won't solve that. Read our post on small roaches in the kitchen, because the same thing applies in a bathroom.

Roaches in the bathroom in Florida: when it's the plumbing

Sometimes it isn't a dry trap. If you run the water and they still come up, or there's a sewer smell in a bathroom where every drain has water in it, a plumber can check for a cracked line or a loose fitting. That's a plumbing repair, not a pest treatment.

If you live in a condo, the gaps around pipes may be in a shared wall. Ask building maintenance to seal them, since some openings in shared walls need fire-rated sealant, not regular caulk. In a single-family home, a gap around the pipe under the sink is often a quick caulk job.

Hosting a rental? Our Airbnb roaches guide has a turnover checklist that includes the drains.