One American Standard, 6L elongate toilet shows slow fill of water into bowl, from under rim, then after 30 plus minutes, toilet flushes itself. I replaced the rubber flapper valve, and problem persisted. I tried petroleum jelly on undersurface of flapper, to improve seal, and problem persists. If overflow tube is cracked, could water enter it near bottom of tank, and cause this problem? If so, how does one replace overflow tube /tank outlet assembly? It all seems to be a single unit.
Thanks for any suggestions.
The next most likely cause is the supply valve assembly in the tank. All it takes is a little build-up of calcium inside the valve and it can work erratically. It's under a $10 part, so troubleshooting is simply replacing it.
The only other simple common problem I can think of is that sometime the small 1/4" diameter tube that fills the bowl is pushed too far down the center tube. This causes a siphon action that keeps drawing water through the main valve assembly. All you need to do to fix this is to make sure that the tube is set near the top of the center tube.
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