01Handle, chain, flapper
Handle is a lever. Chain lifts the flapper off the flush valve seat. Tank water falls into the bowl through the rim and jet.
Too much chain slack = weak lift. Too tight = flapper won't seal (running toilet).
Home & DIY
How a Toilet Actually Works
Flapper, fill valve, siphon trap — the engineering behind every flush
30 min4 photographed stepsBeginner
Replace scrolling with real plumbing literacy: handle lifts the flapper (flush valve), tank water dumps into the bowl, siphonic trapway pulls waste over the bend, water seal blocks sewer gas, fill valve refills tank to the float setpoint. Know why it runs, why it weak-flushes, and which part fails — so the next repair isn't mystery rattling.
What you'll learn
- Tank stores potential energy — bowl does the siphon
- Flapper = flush valve; chain slack matters
- Trapway water seal blocks sewer gas
- Fill valve + float set the waterline
Inside this course
- User interface to tankThe dump.
- Bowl engineeringSiphon and seal.
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First steps from User interface to tank
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02Fill valve and float
After the flush, fill valve opens — refills tank and sends a refill tube trickle into the overflow pipe to restore the bowl seal.
Float (cup or ball) rises and shuts the valve at the waterline mark. High waterline = waste; low = weak flush.
Pro tip. Food coloring in tank, wait 15 min without flushing — color in bowl means flapper leak.
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