Toilet Flapper

A toilet flapper is the rubber or silicone disc at the bottom of the toilet tank that seals the flush valve opening. When you press the flush handle, a chain lifts the flapper, releasing tank water into the bowl. Once the tank empties, the flapper drops back down and seals the opening so the tank can refill. It's the single most commonly replaced toilet part — and a failing flapper is the leading cause of running toilets.

Signs of a bad flapper

• Running toilet: you hear water running into the bowl between flushes — the flapper isn't sealing completely
• Phantom flushes: the toilet refills on its own without being flushed — tank water is draining slowly past a worn flapper
• Food coloring test: put a few drops of food dye in the tank (not the bowl). If color appears in the bowl within 15 minutes without flushing, the flapper is leaking

How much water a bad flapper wastes

A leaky flapper can waste 200 gallons per day — 6,000 gallons per month. At average U.S. water rates, that's $50–$150/month added to your water bill, silently. The EPA estimates that leaky toilets account for over 1 trillion gallons of water wasted in U.S. homes each year.

Flapper replacement

Replacement is a true DIY job: turn off the water supply at the angle stop under the toilet, flush to empty the tank, unhook the old flapper chain and slip the ears off the overflow tube, clip on the new flapper, reconnect the chain (leaving ½ inch of slack), and turn the water back on. The whole job takes 5–10 minutes. Cost: $5–$15 at any hardware store.

Choosing the right flapper

Not all flappers fit all toilets. The universal-fit flapper with adjustable ears fits most 2-inch flush valves. For Kohler, American Standard, TOTO, and Glacier Bay toilets, OEM or brand-compatible flappers seal better. If you've replaced the flapper twice and the toilet still runs, the flush valve seat may be pitted — a $20–$60 fix with a flush valve repair kit, or a full toilet replacement if the toilet is old.