You lifted the lid and saw something wriggling. Now you want to know what it is, whether it can hurt your family, and whether something in your bathroom is broken.
Most worms in a toilet bowl are harmless. Their colour, size and shape give you good clues about which one you have, and whether it points to a plumbing problem.
TL;DR
- Small black or grey worms are often drain fly larvae. They feed on the slime inside drains and toilets.
- One long, thin worm tied in a knot is likely a horsehair worm. It came out of an insect and is harmless to people.
- Small red worms are often bloodworms. They live in still water, so they show up in toilets nobody uses.
- Earthworms that keep showing up can mean soil is getting into a damaged pipe. Have a plumber check.
- Tiny white worms in or on stool are a question for your doctor, not a plumber.
What Are the Worms in My Toilet Bowl?
Worms in a toilet bowl are usually one of five things: drain fly larvae, horsehair worms, bloodworms, earthworms or pinworms. Looks give you clues, not certainty.
Before you flush, take a clear photo. Note the length, the colour, how it moves, and whether you saw it before or after someone used the toilet. That makes the table below easier to use, and it helps a plumber or doctor if you need one.
| What you see | Most likely | Plumbing problem? | What to do |
|---|---|---|---|
| Tiny grey to black worms, about 4 to 10 mm, often several | Drain fly larvae | Sometimes, if they keep coming back | Clean under the rim and the drain. See our drain worms guide |
| One long, very thin dark worm, often curled in a knot | Horsehair worm | No | Flush it |
| Small bright red worms | Bloodworms (midge larvae) | No | Flush that toilet often |
| A pink or brown earthworm | Earthworm | Possibly a damaged pipe | Call a plumber if it happens again or drains are slow |
| Tiny white threads in or on stool | Pinworms | No | See your doctor |
Are Small Black Worms in the Toilet Dangerous?
No. Small black or grey worms in a toilet are often drain fly larvae, and they don't bite.
Abell Pest Control notes that drain flies have not been found to spread disease to people. Breathing in bits of the adult flies has been linked to asthma in some people, though.
The larvae feed on the slimy film that builds up inside drains. In a toilet, that film collects under the rim and in the drain below the bowl.
These are the same larvae people find in showers and sinks. Our guide on how to get rid of drain worms shows you how to clear them out.
Scrub away the slimy buildup under the rim. Flushing may wash away the larvae you can see, but more can appear if the slimy buildup remains. Abell also notes that bug sprays generally won't work. The place they breed has to go.
What if they keep coming back after a good clean? The flies may be breeding deeper in the drain, or in a damp spot nearby.
What Is the Long, Thin Worm Curled Up in My Toilet?
A long, very thin worm that twists into a loose knot is most likely a horsehair worm. It is harmless to you and your pets.
Dr. Heather Proctor, a biologist at the University of Alberta, told rdnewsNOW that young horsehair worms grow inside insects such as crickets and grasshoppers. When the adult is ready, it makes the insect look for water. Then it leaves the insect's body. The adults don't even have mouths.
So a horsehair worm in your toilet usually means an insect ended up in the bowl. It does not mean your pipes have a problem.
Flush it and move on.
Why Are There Small Red Worms in My Toilet?
Small red worms in a toilet are often bloodworms, the larvae of midges. They are harmless.
The City of Edmonton explains that their red colour comes from haemoglobin, the same protein that makes blood red. It lets them live in water with very little oxygen.
That is why they turn up in still water. You are most likely to find them in a toilet that sits unused for weeks, such as a basement or guest bathroom.
Flush that toilet often and clean the bowl. That takes away the still water they need.
What Do Earthworms in the Toilet Mean?
One earthworm on its own is worth watching, not worrying about. First, ask whether it could have fallen in from nearby, such as from a window, a plant or someone's shoe. If they keep showing up, soil may be getting into your plumbing.
Earthworms live in soil. If they keep appearing and there's no obvious way they could have fallen into the bowl, a damaged underground drain pipe is one possible explanation.
Watch for these other warning signs:
- You find earthworms more than once
- Several drains in the house are slow
- You smell sewage in the basement
- The toilet gurgles when you flush or run water nearby
If you notice any of these, don't guess. Our plumbing repair team can find the cause and explain what the repair involves.
Is Your Toilet Part of the Problem?
Sometimes. Drain fly larvae can grow in the slime under a toilet's rim or in the drain below it. That is a cleaning job, not a repair.
A leaking toilet is a different problem. Water at the base can mean a failed seal under the toilet, and a toilet that rocks may be loose. A leak leaves the floor damp, and damp spots can attract drain flies.
Our post on why your toilet is leaking covers the signs in more detail. One tip: beads of water all over a cold tank are usually condensation, which is normal. Water dripping from one spot is not.
Replacing the seal means lifting the toilet off the floor and setting it back down on a new seal. That is a job for a plumber. When we look at a toilet like this, we check the seal at the base, the tank connections and how the drain flows. After any toilet repair, we test the seal and the flush before we leave.
Could the Worms Have Come from Your Body?
Sometimes, yes. Tiny white thread-like worms in or on stool, often with itching, may be pinworms. That is a question for a doctor, not a plumber.
The Canadian Paediatric Society says pinworms are very common in children. They are usually mild, but they can cause itching and lost sleep. Your doctor can test for them and treat them with medicine. Having them doesn't mean anyone is dirty.
When Should You Call a Plumber About Worms in the Toilet?
Call a plumber when:
- Worms keep coming back after a good clean
- Drains are slow, gurgle or smell like sewage
- You see signs of a leak around the toilet
You don't need a plumber for one horsehair worm, bloodworms in a toilet you rarely use, larvae that stop after a good clean, or pinworms.
Most of the time, you can flush, clean and move on. If the worms keep coming back after cleaning, a plumber can check for hidden drain or moisture problems.
PlumbWize's licensed plumbers serve Burlington, Oakville, Hamilton and nearby communities. We explain the work and the price before any repair begins.
