Follow our easy, step-by-step instructions to solving this common commode conundrum

Time to solve the case of the running toilet once and for all. It’s a quick fix, whether the problem stems from the flapper, the float or the fill valve.

If the Problem Is the Flapper

Step 1: The flapper, a rubber piece inside the tank that lifts to release water into the bowl when you flush the toilet, corrodes over time. To see whether yours has deteriorated, do this simple test: After taking the lid off the tank, stick your hand in (don’t worry, the water’s clean!) or use a stick and push down on the flapper. If the toilet immediately stops running, voila! Your flapper isn’t sealing the water properly on its own and needs to be replaced.

Step 2: Turn off the water to the toilet—the shut-off valve (a silver knob) should be on the wall, possibly close to the floor, directly behind the tank.

Step 3: Flush the toilet to drain any water out of the tank and bowl.

Step 4: Unhook the flapper from its chain and attach a new one (follow package directions). Be especially careful when adding or removing links to the chain. It should be the same length as the one on the previous flapper. If it’s too short or too long, the chain will prevent the flapper from operating the flush mechanism properly.

If the Problem Is the Float

Step 1: A toilet tank contains a plastic ball that floats on top of the water to indicate when the tank is full. But if the float is set too high, the water level will rise above the overflow tube or pipe, causing the tank to continuously drain. You can test your float by flushing the toilet and seeing where the water stops. The water level should be one-half to 1 inch below the top of the overflow tube; if it’s higher, the float needs adjusting.

Step 2: Bend down the arm, or rod, that connects the float to the pump or turn the small screws on top of the valve to adjust it. This will lower the float, so the pump turns off sooner and your toilet stops running.

If the Problem Is the Fill Valve

Step 1: If you’ve adjusted the float and the water is still running, try replacing the fill valve, the mechanism that allows the tank to fill with water to the right level.

Step 2: Turn off the water to the toilet—the shut-off valve (a silver knob) should be on the wall, possibly close to the floor, directly behind the tank.

Step 3: Flush the toilet to drain any water out of the tank and bowl.

Step 4: Disconnect the water supply line and unscrew the lock nut from outside the tank. Remove the fill valve.

Step 5: Install a replacement valve according to package directions and adjust the float to the correct water level.