Replace a Toilet Flapper, Fill Valve and Supply Line Step by Step

Brent Clifford, a master plumber and trainer at Eco Plumbers in Columbus, Ohio, shows how to replace the water-regulating parts in a toilet tank: the flapper, the fill valve and the supply line. The job starts with a test, not a purchase.

Testing the flapper

Dye tablets, available at any hardware store, go into both sides of the tank. They dissolve over a few minutes and turn the water dark blue. After about five more minutes without flushing, any blue in the bowl means the flapper or flush seal is leaking. Here a spot of blue appeared, and the flapper's color was washed out; the plastic should be a deep, dark red. The whistling noise the homeowner described pointed to the fill valve, where a diaphragm and pin that don't open fully can cause vibration.

Shutting off and removing parts

The water is isolated at the emergency shut-off (clockwise closes it), and the tank is drained by holding the handle down. The supply line is loosened with a wrench, with rags ready for escaping water. Its rubber seals were soft and spongy on one end and nearly gone on the other. Brent's practice is to replace the supply line any time the back of the toilet is worked on, since separating the connections compromises those seals. The braided line has a rubber hose inside, and the braid works like a Chinese finger trap to keep it from bursting.

The flapper's air chamber

The universal flapper has an air chamber with a selector dial that meters how fast it comes back down. A smaller hole makes it float longer. The back lists settings for brands including Kohler and Sterling; for this Sterling the options were six, three and two, to be found by trial and error. The flapper has nine steps. Here the toilet flushed fully at nearly every setting, which Brent attributed to a fairly short overflow tube.

Installing the fill valve

The Fluidmaster 400A universal fits most standard toilets and telescopes to suit tall or low-profile tanks. The box includes a troubleshooting guide, and the kit's tube creates an air gap at the overflow so bleach tablets can't siphon back into the water supply. The locknut under the tank should be snug, not extremely tight, and the valve head should have clearance from the tank wall. The new supply line is attached to the tank first, hand tight, then snugged with a wrench.

Chain length and water level

The chain is pulled taut before the flapper starts to rise, then given one link of slack. Too long and the flapper won't lift enough; too short and the toilet constantly runs. Excess chain is hooked back up so it can't get caught under the flapper. The water should settle about a half inch to 7/8 inch below the top of the line, or at the manufacturer's fill line. Brent checks several flushes, and says it usually takes three to six to dial in. A second round of dye tabs confirms the seal later.

The trip lever nut is reverse threaded: righty loosen, lefty tighty.