Centipedes in your bathroom almost always come from somewhere else in your home, not up through the drain. They’re drawn to bathrooms because humidity spikes after every shower, creating the damp, dark conditions they need to survive. If you’re seeing them regularly, it signals both a moisture issue and a population of other insects living in your walls or crawl spaces.
They Don’t Come Up Through the Drain
The most common assumption is that centipedes crawl up from the plumbing, but this isn’t what happens. Drains have water-filled traps (the curved section of pipe underneath) specifically designed to block sewer gases, and centipedes can’t hold their breath long enough to swim through that standing water. Rats can manage it. Centipedes cannot.
What actually happens is simpler and a little comical: a centipede hunting along the rim of your tub or sink slips on the smooth surface, slides in, and can’t climb back out. The porcelain walls are too slick for their legs to grip. So when you find one sitting in your bathtub at 2 a.m., it didn’t arrive from below. It fell in from above and got stuck.
How They Get Into Your Home
House centipedes enter through the same gaps and cracks that let every other bug inside. They have flat, flexible bodies and can squeeze through surprisingly small openings. Common entry points include:
- Foundation cracks in walls and slabs
- Gaps around pipes and cables where they penetrate exterior walls
- Poorly sealed door thresholds and worn weatherstripping
- Openings around vents in crawl spaces and attics
- Gaps around basement windows and window wells
- Torn or loose window screens
Once inside, they migrate toward moisture. Bathrooms, basements, crawl spaces, the area under kitchen sinks, and spaces behind washing machines are their preferred zones. In bathrooms specifically, small gaps around tubs, toilets, and sink pipes give them hiding spots during the day. They’re nocturnal, so you’ll almost never see one during daylight hours unless it’s been disturbed or trapped.
Why Bathrooms Specifically
House centipedes need humidity above 50% to survive. Unlike most insects, they don’t have a waxy outer coating to retain moisture, so dry air kills them relatively quickly. Bathrooms deliver reliable humidity spikes every time someone showers or runs hot water, making them the most consistently damp room in most homes.
But moisture alone isn’t the full picture. Centipedes are predators. They eat silverfish, cockroaches, spiders, carpet beetle larvae, and other small bugs. If centipedes keep showing up in your bathroom, it means the humidity is high enough to support both them and a population of prey insects. A single sighting might be a wanderer. Repeated sightings mean your home is hosting enough other pests to sustain a food chain.
Are They Dangerous
House centipedes are venomous, but their bite is rarely a concern for humans. They’re fast and fragile, built to chase down insects rather than defend against people. A bite, if it happens at all, typically causes localized pain, some redness, and mild swelling that resolves within a few days. Think bee sting level, not medical emergency. Severe reactions are extraordinarily rare and associated with larger tropical centipede species, not the house centipedes you find in North American bathrooms.
In practical terms, house centipedes are more helpful than harmful. They actively hunt cockroaches, silverfish, and spiders. Killing every centipede you see without addressing the underlying conditions just removes a predator while the prey insects that attracted it remain.
How to Keep Them Out
Lower the Humidity
This is the single most effective step. Centipedes can’t survive when indoor humidity drops below 50%. The EPA recommends keeping indoor levels between 30% and 50% for general pest prevention. Run your bathroom exhaust fan during and for at least 15 to 20 minutes after every shower. If your bathroom lacks a fan, crack a window or add a small dehumidifier. In basements and crawl spaces, a standalone dehumidifier makes a dramatic difference. Fix any dripping faucets, running toilets, or leaking pipes, since even small, persistent water sources keep humidity elevated in enclosed spaces.
Seal Entry Points
Inspect where pipes and wires enter your bathroom walls and caulk any gaps. Silicone or acrylic latex caulk works well for most cracks around windows, doors, and baseboards. Acrylic latex is easier to work with because it cleans up with water and can be painted over. For larger gaps around utility penetrations, expandable foam, steel wool, or copper mesh will fill the space. Check the base of exterior doors for light gaps (even 1/16 of an inch is enough for insects to pass through) and install door sweeps if needed.
Reduce Their Food Supply
Because centipedes follow their prey, eliminating the other insects in your home removes their reason to be there. Keep bathrooms clean and dry. Store paper products and cardboard (which attract silverfish) away from damp areas. Address any cockroach or silverfish problem directly, and the centipede population will decline on its own as the food source disappears.
Exterior Barriers
For persistent problems, treating the outside perimeter of your foundation with a residual insecticide creates a chemical barrier. Apply it in a band two to six feet wide along the ground and two to three feet up the foundation wall, concentrating around doors, garage entrances, crawl space openings, foundation vents, and utility penetrations. Hardware stores carry ready-to-use formulations designed for this purpose. This supplements sealing but doesn’t replace it. Caulking and weatherstripping are longer-lasting solutions than chemical treatments alone.