What are the common signs that indicate a toilet fill valve needs replacement?

Common Signs a Toilet Fill Valve Needs Replacement

Water keeps flowing into the tank/bowl even when not flushed (the valve fails to shut off). Test: Turn off the toilet’s water supply—if the running stops, the fill valve is the culprit (not the flapper).

The tank takes more than 2 minutes to refill (normal is 30–60 seconds). This is usually from mineral buildup clogging the valve’s internal passages (cleaning the filter won’t fix it long-term).

Whistling, hissing, or "water hammer" (banging) when the tank refills. These sounds mean internal seals or springs are worn—temporary fixes (e.g., cleaning) only quiet it briefly.

Water pools on the floor behind the toilet, or dampness is visible under the tank. This is caused by a cracked valve body or worn gasket (a critical issue that risks water damage).

The float (ball/cup that controls water level) is cracked (fills with water and sinks), or stuck (won’t rise/fall to shut off water). While the float can be replaced alone, a damaged float often means the valve is near total failure.

Water spills into the overflow tube (tall plastic pipe in the tank) when full. This wastes hundreds of gallons of water daily and requires immediate valve replacement.

Fill valves last 5–7 years on average. If your valve is older and you’ve fixed small issues (e.g., stuck float, clogged filter) multiple times, replacement is cheaper and more reliable.