Why won't my toilet flush?

A flush is a tank of water dumped into the bowl all at once. The rush of water pulls everything in the bowl down a curved pipe built into the toilet, and out to the drain under the floor.

1. The handle and chain. Pushing the handle lifts an arm inside the tank, which pulls a chain.
2. The flapper. The chain lifts this rubber flap, and the tank water rushes out.
3. The fill valve. After the flush, it lets water back in until the float tells it the tank is full.
4. The holes under the rim. Water pours into the bowl through small holes all around the rim.
5. The curve inside the toilet. A built-in S-shaped channel that holds water in the bowl. Most clogs stop here.

So a toilet that won't flush usually has one of these:

• No water in the tank: the valve, the fill valve, or the house's water.
• Nothing lifting the flapper: the chain or the handle.
• Not enough water rushing in: a low water level, a loose chain, or crusty rim holes.
• Nowhere for the water to go: a clog in the toilet, or in the main drain.

If the toilet runs all the time instead, our guide to a toilet that keeps running covers the flapper, chain and fill valve in more detail.

Water on the floor around the toilet? See our guide to a toilet leaking at the base.

This one test skips the tank, so it tells you whether the drain itself is slow.

1. Fill a bucket with about a gallon of water.
2. Pour it into the middle of the bowl quickly, all at once.
3. Stop pouring if the water starts to rise.

• The bowl empties with a strong whoosh: the drain is fine. The problem is in the tank or the rim holes: a low water level, a loose chain, or crusty holes.
• It drains slowly, or the water rises: the drain is partly blocked. Start with a plunger.

• The water in the bowl is rising toward the rim. Turn the valve behind the toilet to the right.
• Water comes up in the tub or shower when you flush.
• It smells like sewage, or several drains are slow at once.
• Something hard went down, like a toy or phone.
• You poured in drain cleaner and it's still clogged. Don't plunge it.

Don't pour drain cleaner into a toilet. The Drano Max Gel label says not to use it in a toilet at all.

Most toilet fixes are cheap parts. HomeGuide lists $130–$300 for a typical toilet repair, about $220 on average. A new toilet installed runs $350–$800. Ask yourself three things:

• Is the bowl or tank cracked? A cracked toilet gets replaced, not repaired.
• Is it a clog? HomeAdvisor lists $110–$275 to unclog a toilet. That's a repair, not a reason for a new toilet.
• Is the whole tank worn out? HomeGuide lists about $300 to rebuild all the parts inside. If the toilet is old and clogs often, a new one may be worth it.

Example: $150 to clear a clogged toilet is fair. Being told you need a new toilet because of one clog is worth a second opinion.