Fully open the water supply's shutoff valve to assure that there is adequate water pressure and volume.
Clear any obstruction in the toilet trapway. Push a closet auger into the bowl opening until you feel an obstruction. Turn clockwise to screw the auger into the obstruction and draw it out.
Use a mirror to inspect the holes on the rim's underside during a flush. Clear any clogged holes with a piece of copper wire.
Adjust the water level until it's at the water line marked on the tank or overflow tube. Flush to test. To adjust water levels on plunger- or diaphragm-type fill valves with a float ball, either turn the adjustment screws on those models that have them or use both hands to bend the arm--down to lower the water level, up to raise it. For floatless models, turn the adjustment screw about a half turn at a time. For float-cup fill valves, pinch the spring clip to raise or lower the float.
Things You Will Need
- Closet Auger
- Small Mirror And Copper Wire
- Wear rubber gloves to protect your hands.
- At the proper height, the water level should be no more than 1/2 inch (12 mm) below the top of the overflow tube. If the tube's too long, cut it with a hacksaw. Some tubes unscrew. If yours doesn't, remove the flush valve to make the cut.