Things You'll Need
Replacement flush valve seal
If you notice your toilet seems to be topping off several times an hour, it is usually a sign that the flush valve seal is worn. There are many types of flush valves. A Mansfield flush valve does not use a flapper and chain; instead, it has a straight float that lifts completely up when you flush the toilet. The flush seal on a Mansfield flush valve is accessible without removing the tank.
Turn the toilet water supply off to the tank. The shut off valve is on the main water line coming from the wall behind the toilet. Turn the valve clockwise to shut the water off to the tank.
Lift the toilet tank lid off of the toilet and set the lid on a flat surface. Flush the toilet, and hold the flush handle down to allow as much water to leave the tank as possible.
Soak up all the remaining water in the tank with a towel. Wring the water out into a bucket and continue to soak up all the water in the tank.
Pull the fill tube out of the top of the flush valve. The flush valve is the valve assembly in the center of the toilet tank. The fill tube connects to a nipple on the white flat disk on top of the flush valve. Grab the tube with your fingers and pull the tube straight off the disk.
Unscrew the white disk from the top of the flush valve with your fingers. Pull the disk off the Mansfield flush valve and set the disk aside.
Grab the flush valve float and lift the float off the flush valve. The flush handle stem attaches to the float. While lifting the float out, turn the float slightly to remove the flush handle stem from the retainer on the float.
Pull the red rubber flush valve seal out of the flush valve. The seal is the first rubber seal you see at the bottom of the flush valve. Mansfield flush valve seals are usually red. The seal fits between a groove and will pull out with your fingers.
Position the replacement flush valve seal over the bottom of the flush valve. Insert one side of the seal into the groove. Hold the seal between your finger and thumb and pull the seal down to set the rest of the seal into the groove.
Clean the bottom of the flush valve float with a rag to remove any debris. Place the flush valve float back over the flush valve while maneuvering the flush handle back into the retainer.
Place the disk back on top of the flush valve assembly and secure the disk by screwing the disk clockwise with your finger. Push the fill tube back into the disk until the bottom of the tube is flush with the disk.
Turn the water supply back on to the toilet.