Can Rats Swim Up Toilets? Yes, and How Often It Happens
Yes, rats can swim up toilets: a Norway rat can travel through sewer lines, climb inside vertical pipes 1.5 to 4 inches wide and dive through the water trap in the bowl. It is uncommon, and we found no US agency that publishes a count, but it is real enough that Seattle’s sewer baiting programme responds to rat-in-toilet complaints. It usually follows a broken side sewer, heavy rain or flooding, or food washed down drains. If it happens, keep the lid shut, add dish soap and flush.
The question sounds like an urban legend, and plenty of what is written about it is. Breath-holding times and household percentages get repeated without a source. The physical abilities, though, are documented by university extension engineers, and a county health department has written instructions for exactly this situation. This guide sticks to those.
How a rat gets into a toilet
| Stage | What happens | Source |
|---|---|---|
| 1. Into the sewer | Rats enter sewers at outlets and through manholes, catch basins, broken pipes and drains | Nebraska wildlife damage handbook |
| 2. Drawn towards your line | Rats follow the scent of food washed down drains; old side sewers raise the risk | Public Health, Seattle and King County |
| 3. Pushed in | Flooding or heavy rain may drive rats into the side sewer between house and street | Public Health, Seattle and King County |
| 4. Up the pipe | Rats climb inside vertical pipes 1.5 to 4 inches across and travel in sewer lines against a substantial current | University of Nebraska Extension G1530 |
| 5. Through the trap | Rats dive through water traps in plumbing; water traps do not stop Norway rats | University of Nebraska Extension; Nebraska handbook |
| 6. Into the bowl | Kitchen pipes are too narrow, so the toilet is the usual way up | Public Health, Seattle and King County |
UC IPM’s Pest Notes on rats confirm the route in general terms: rats can get into buildings by “swimming through sewers and entering through toilets or broken drains.”
What to do if a rat is in your toilet
Public Health, Seattle and King County gives these steps:
- Stay calm and keep the lid down so the rat cannot jump out.
- Squirt liquid dish soap into the bowl. It breaks the surface tension and degreases the rat’s fur so it cannot stay afloat.
- Flush, several times if needed. The rat usually goes back down the way it came.
- If it will not flush, keep the lid closed and call a pest control company.
- If it escapes, close the bathroom door and set a rat trap.
- Report it. In Seattle, call Public Health; elsewhere, contact your public utilities department or sewer district, listed on your utility bill.
Afterwards, clean the bowl and seat with gloves on. CDC’s rodent clean-up guidance is to spray with a solution of 1 part bleach to 9 parts water, or an EPA-registered disinfectant, and let it soak for 5 minutes or as the label directs. Do not pour rat poison or other pesticides down a toilet; UC IPM’s Pest Notes say never to dispose of pesticides that way.
Which rats, and why the toilet
The rat in a toilet is almost always a Norway rat, also called the sewer rat. UC IPM says Norway rats are the more powerful swimmers while roof rats are the better climbers, although roof rats “may even occupy sewers” when elevated nest sites are scarce. When Norway rats invade buildings, UC IPM says they usually live in the basement and ground floor, the parts closest to the sewer. Our guide to roof rats covers how the other species gets in, usually from above.
The Nebraska wildlife damage handbook explains why sewers suit them: domestic sewage from an average community provides enough food to sustain a large number of rats, and the problem is usually worst where sanitary sewers are interconnected with storm sewers, giving rats multiple entry points.
How often do rats come up toilets?
Nobody knows precisely, and you should be wary of anyone quoting a percentage. We found no study or agency dataset giving a rate per household; a figure of 2 to 3 per cent of urban households circulates online with no source behind it.
Complaint data does not help much either. New York City’s 311 system, one of the largest rodent complaint records in the country, sorts rodent complaints into five categories: rat sightings, mouse sightings, signs of rodents, conditions attracting rodents and rodent bites. None is specific to toilets, so rat-in-toilet reports are folded into sightings. Our rodent complaint analysis covers the full record.
What the evidence does show is where the risk concentrates:
- Homes with old or broken side sewers. King County names old side sewers and plumbing as a risk.
- After heavy rain or flooding, which may drive rats into side sewer lines.
- Neighbourhoods with combined sewers, where storm and sanitary lines connect.
- Kitchens that send food down the drain. King County advises using garbage disposals as little as possible and never pouring grease or oil down the drain.
How often do rats come up toilets at night?
Rats are mostly nocturnal. Los Angeles County’s environmental health bulletin puts most activity between about half an hour after sunset and half an hour before sunrise, so night is when rats are most likely to be moving through pipes. No source gives a nightly rate.
How long can rats swim before drowning?
A long time. The Nebraska handbook says rats are excellent swimmers “capable of staying afloat up to 72 hours,” and University of Nebraska Extension’s rodent-proofing guide says they can swim half a mile in open water. That is why a rat that has climbed a drain does not drown in the trap.
The often-quoted claim that rats hold their breath for three minutes is harder to pin down. We could not find it in any extension, government or peer-reviewed source, so we do not repeat it as fact. The documented ability that matters is simpler: rats dive through plumbing water traps.
Can rats climb walls?
Yes, rough ones. University of Nebraska Extension says rats and mice can climb almost any rough vertical surface, such as wood, brick, concrete and weathered sheet metal, and run along wires, ropes, vines and trees. Rats can also climb the outside of pipes and conduit up to 3 inches across, jump 36 inches vertically and 48 inches horizontally, and reach up to 13 inches along a vertical wall.
| Surface | Can a rat climb it? |
|---|---|
| Brick, concrete block, rough wood | Yes, easily |
| Weathered sheet metal | Yes |
| Pipes and conduit up to 3 inches across (outside) | Yes |
| Larger pipes fixed close to a wall | Yes, bracing against the wall |
| Vertical pipes 1.5 to 4 inches across (inside) | Yes |
| Aluminium sheet metal band 12 to 18 inches wide | Used by extension engineers as a climbing barrier |
Can mice come up through the toilet?
It is not documented the way it is for rats. The extension rodent-proofing guidance lists swimming half a mile, diving through plumbing traps and travelling in sewer lines among the abilities of rats, not house mice, and none of the agency guidance we read describes mice entering through toilets. A mouse found in a toilet bowl is more likely to have fallen in from the room. If the creature you found in the bowl or drain is small and many-legged rather than furry, our guide to bugs in the bathroom will identify it.
How to stop rats coming up the toilet
- Keep the lid down, especially after heavy rain, since King County says flooding can drive rats into side sewers.
- Keep food and grease out of drains. King County suggests cleaning the kitchen sink drain monthly with a cup of baking soda followed by a cup of vinegar, or a cup of bleach, then rinsing with boiling water. Use one method at a time.
- Have the side sewer inspected. Seattle Public Utilities recommends inspecting it every 8 to 10 years; in Seattle the property owner is responsible for its repair. A licensed contractor fixes breaks.
- Watch for a burrow that keeps reopening. King County says a burrow in the yard that reopens after you fill it can be a sign of rats in the sewer. Professionals pour coloured dye into the burrow; if it shows up in a nearby manhole, the side sewer may be broken.
- Fit grates on floor drains. The Illinois Department of Public Health advises tight-fitting grates on floor drains and sewer pipes, with openings under a quarter inch.
- Ask a plumber about a dedicated one-way rodent flap. Be careful with the term backwater valve. Under the plumbing code section Portland cites, backwater valves must “remain open during periods of low flows,” so a standard flood valve is built to shut only when sewage backs up, not to stop a rat.
Will bleach stop rats in the toilet?
No source shows that bleach repels rats. King County lists bleach only as one way to clean food residue out of a kitchen drain, which removes the scent that draws rats along the pipes. Pouring bleach into the toilet will not block the sewer line. If you use bleach to clean, follow the label.
When to call a professional
A rat that will not flush, repeat visits, a burrow that keeps reopening, or rats in the walls or under a slab need a licensed pest professional, and a broken sewer line needs a licensed plumber or sewer contractor. Because the source is the sewer, the fix is usually structural, not chemical. Typical prices are in our guide to rodent removal costs, and what draws rats to a property in the first place is in what attracts rats.
Frequently asked questions
How do you know if a rat is in your toilet?
Usually you see it: a wet rat in the bowl, most likely at night or early morning since rats are mainly nocturnal. Signs that rats are using your sewer line include a burrow in the yard that reopens after you fill it, which King County names as a warning sign, plus droppings or gnaw marks in the bathroom. Keep the lid down and call your sewer district or a pest professional.
What surfaces can rats not climb?
Smooth, hard surfaces they cannot grip. University of Nebraska Extension says rats and mice climb almost any rough vertical surface, including wood, brick, concrete and weathered sheet metal, and climb inside vertical pipes 1.5 to 4 inches across. To stop rats climbing walls and corners, it recommends attaching aluminium sheet metal bands 12 to 18 inches wide, which give them nothing to grip.
What do rats hate the worst?
No scent has been shown to drive rats away. The Nebraska wildlife damage handbook says chemical repellents are seldom practical for rat infestations, and UC IPM says rats quickly get used to repeated sounds, which makes ultrasonic devices ineffective. Rats are wary of new objects and avoid them for days, but that fades. Removing food, water and shelter, and sealing gaps, is what works.
What are three signs that you have a rat infestation?
Droppings, gnaw marks and burrows are the three most reliable. UC IPM says rats leave tooth marks about 1/6 inch (4 mm) wide, larger than a mouse’s scratchy marks, and that Norway rat burrows appear along foundations, under rubbish or woodpiles and around gardens. Other signs on its list include smudge marks where fur rubs on walls and pipes, and noises in the attic. Our droppings identification guide separates rat from mouse droppings.
Sources
- Public Health, Seattle and King County, Keep rats out of your toilet and sewer, and the Seattle Sewer Baiting Program.
- University of Nebraska Lincoln Extension, Rodent-Proof Construction: Structural, G1530, revised 2009.
- Internet Center for Wildlife Damage Management, Norway Rat Damage Prevention and Control Methods, from Prevention and Control of Wildlife Damage, University of Nebraska, 1994.
- University of California Statewide IPM Program, Pest Notes: Rats, Publication 74106.
- Centers for Disease Control and Prevention, How to Clean Up After Rodents.
- Illinois Department of Public Health, Rat Fact Sheet: Norway Rats.
- Los Angeles County Department of Public Health, Environmental Health, Are You Attracting Rats and Mice to Your Yard?
- City of Portland, Permitting and Development, Backwater Valves (Oregon Plumbing Specialty Code section 710).
- NYC 311 Service Requests, NYC Open Data, Rodent complaint descriptors, checked October 2026; The Pest Control Brief, Rat Complaints in New York and Chicago, 2026.
