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Toilet tank keeps hissing after the water reaches the fill line
A brief hiss while a toilet tank refills seems different from a steady hiss after the tank is full. How long should the sound continue before it’s worth investigating?
Would checking whether water is entering the overflow tube help identify whether the fill valve is still letting water in? I’m also curious whether a trickle into the bowl tells you anything on its own, or whether you’d need to determine where that water is coming from.
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A hiss while the tank is actively refilling is normal; there’s no universal number of seconds to use. If it continues after the tank appears full and the sound doesn’t stop, check for ongoing water movement. Water entering the overflow tube suggests the tank is still filling or overfilling. A bowl trickle alone doesn’t pinpoint the cause - you’d need to see whether water is spilling through the overflow or leaking past the flush valve into the bowl.
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