I have the fluidmaster 400. Recently started slow leaking. Every 7 minutes it refills about an inch of water. I did the dye test and sure enough water leaks into the bowl. So would this rule out everything other than replacing the flapper?

Toilet is less than a year old so I'm surprised the flapper is leaking.

Thanks for any feedback!

Make sure the flapper is sitting straight on the rim of the tank's drain hole and that the upper edge of the drain rim is smooth (no rough spots from hard water deposits). Also, there should be some slack in the chain or plastic string that attaches from the flapper up to the flush handle arm. If there is no slack the flapper may not be closing all the way down.

If all that checks out ok then replace the flapper with a good quality one. The flapper doesn't last forever, will lose flexibility over time due to sitting in water.

The Fluidmaster fill valve probably isn't leaking, it is refilling the tank because the tank water is leaking out. If the Fluidmaster fill valve is leaking and doesn't shutoff then the water level in the tank will increase until it starts going into the overflow tube near the center of the tank. That's a different problem.



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You may or may not use them but any in-tank cleaners will definitely shorten the lifespan of a tank flapper, water quality also has an effect on them.