A toilet is controlled by two valves, one to operate the flushing mechanism and one to fill the tank after the toilet has been flushed. If your Kohler toilet runs constantly after a flush, it means there is a problem with your filler valve. The repair can be as simple as adjusting the fill valve float or replacing a worn-out washer in the valve, or you may need to replace the entire valve assembly. If you have to replace the entire valve, don't worry. It is a procedure that can be accomplished easily, and Kohler provides replacement parts at a low cost.
Adjust the float in the toilet tank. Pinch the spring clip on the float and slide it down the filler valve, making sure it is located an inch below the top of the overflow tube. Flush the toilet and see if this has solved the problem. If issues persist, move on to the next step.
Flush dirt and debris from the valve by removing the cap from the top of the fill valve and running the water supply for a few seconds. Turn the knob on the main supply line under the tank to engage water flow.
Check the washer in the cap for cracks and wear while it is removed from the fill valve. Remove a damaged washer by prying it loose with a screwdriver. Push a new washer into place and reinstall the valve cap. Test by flushing the toilet to see if the problem has been corrected. If not, you will need to replace the filler valve.
Turn off the water supply to the toilet and flush the toilet, holding the flush valve open to completely drain the tank. Use a sponge to remove any leftover water from the tank.
Unscrew the coupling nut connecting the water supply line to the bottom of the tank and fill valve. Hold the valve in place with locking pliers as you turn the nut with an adjustable wrench.
Remove the valve by unscrewing the locknut on the underside of the tank.
Measure the height of the overflow tube. Always measure to the top of the tube where the opening is.
Adjust the new fill valve's height so that the "critical level" is 1 inch higher than the overflow tube. Do this by holding the base of the fill valve and twisting the top.
Insert the bottom of the fill valve through the hole in the tank and press down while tightening the locknut. Reconnect the supply line with the coupling nut and repeat Step 2 to flush the new valve, checking for any leaks.
Attach the fill tube to the valve, cut to size and attach it to the overflow tube.
Adjust the float as in Step 1 so that the water level will be set to 1 inch below the top of the overflow tube.
Turn on the water supply to fill the tank.