toilet fill valve resized 600A running toilet is horribly frustrating. If you can hear the toilet tank filling continuously, lift the lid and take a look around. In most cases, I end up replacing the fill valve and flapper, but you may be able to get away with just adjusting the fill valve to turn it off earlier. If the fill valve is continuously running, it is a sign that it can’t quite turn off, and you should replace it. If the water continues to flow, it will fill up to the point of flowing down the flush valve in the center of the tank. Yes, it will waste a lot of water.

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If you have an old style ballcock, you can bend the metal arm downward. If you have a newer fluidmaster style, adjust the float downward. Both of these will cause the valve to shut off earlier than it normally has. It may work, or you may need to replace it.

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If you hear the water filling sporadically, I would also replace the flapper as this indicates that water is slowly leaking out of the tank to the point the fill valve turns on to refill the tank. Adjusting the fill valve is really more of a band-aid approach if the valve has been working without problems in the past.

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