How to Adjust a Toilet Fill Valve

Identify the Toilet Fill Valve

The toilet fill valve is located under the toilet tank lid, in the back of the toilet. There are at least five different toilet flush valve types, with the float cup fill valve and the ballcock fill valve being the most common:

• Plunger/Piston Ballcock Valve: A floating ballcock on the surface of the water is attached to a metal rod. When the water rises, the rod lowers a plunger at the bottom of the tank to stop the flow of water.
• Diaphragm Ballcock (Brass or Plastic): A floating ballcock on the surface of the water triggers a diaphragm seal inside a round valve body to turn the water flow on or off. The diaphragm casing may be either brass or plastic and it is raised above the surface of the water.
• Float Cup Fill Valve: A plastic cylinder float moves up and down with the changing water level. When the water rises and the cup reaches the top, the water supply to the tank shuts off.
• Internal Float Fill Valve: A plastic box on top of a plastic stem has a float located within the stem. The float is not visible, but it does raise and lower according to the level of the water.
• Floatless or Pressure-Activated Fill Valve: A mechanism senses pressure rather than relying on a float or ballcock. This type of valve is submerged in the tank water.

How to Adjust a Plunger/Piston Ballcock

Adjust a plunger/piston ballcock fill valve easily by bending the float rod up or down. First, flush the toilet to empty the tank. Work quickly to bend the float rod before the tank fills again.

1. Adjust the Float Rod

   With the toilet tank empty, bend the float rod up to increase the water fill level in the tank or bend it down to lower the fill level. The float rod is delicate metal, so bend it gently.

   Tip

   It's possible to bend the float rod before the tank fills again. But you can give yourself more working time by turning off the water supply valve at the base of the toilet, near the floor. Just remember to turn it back on before flushing the toilet.

2. Watch the Water Level

   Flush the toilet. Keep the toilet lid off while the tank refills. The water level must be below the top of the tank's overflow tube. If it is not, repeat the previous step and continue to adjust until the water level is just below the top of the tube.

How to Adjust a Brass Diaphragm Ballcock

Adjust a brass diaphragm ballcock toilet fill valve by bending the metal float rod up or down to control the level of the water in the tank. While this can usually be completed before the tank refills, turn off the water supply valve at the toilet base if you need more time.

1. Adjust the Water Level

   Remove the toilet tank lid. Flush the toilet. Adjust the water level by gently bending the brass float rod up to increase the water fill level or down to lower the water fill level. 

2. Watch the Water Level

   Flush the toilet again. Watch the water rise in the tank until the ballcock floats. When the water stops flowing, the water level must be below the top of the tank's overflow tube. If not, make small adjustments to the float rod until the water level is where it should be.

How to Adjust a Plastic Diaphragm Ballcock

Adjust a plastic diaphragm ballcock toilet fill valve by turning the adjustment screw on the top that adjusts the height of the float rod and ball. Because the float rod is plastic, it cannot be bent into shape.

1. Turn the Screw Clockwise or Counterclockwise

   Using a screwdriver, turn the screw at the top of the valve. Turning the screw counterclockwise raises the water level, while turning the screw clockwise lowers the water level.

   Tip

   Adjust only by turning the screw. Bending the plastic float rod is ineffective and may break the rod.

2. Watch the Water Level

   Flush the toilet. Watch the water lever rise until it stops. The water level must be below the top of the tank's overflow tube. Continue adjusting as needed to get the appropriate water level.

How to Adjust a Float-Cup Fill Valve

Adjust a float-cup toilet fill valve by turning an adjustment screw with a screwdriver. This adjusts the height of the float rod and ball. The float-cup fill valve is the current standard design used on most new toilets.

1. Find the Plastic Screw Mechanism

   On some float cup valves, there is a plastic screw mechanism you can turn to raise or lower the float. Find this mechanism and turn it to raise or lower the float.
   

2. Slide the Float up or Down By Adjusting the Screw

   To lower the water level, slide the float down on the actuating rod by turning the screw clockwise with a screwdriver. To raise the water level, slide the float up on the rod by turning the screw counterclockwise with a screwdriver.

3. Watch the Water Level

   With the toilet lid still off, flush the toilet. Watch the water level rise until it stops. The water level should be about 1 inch below the top of the overflow tube and the critical level mark on the fill valve.

   Tip

   Some float cup valves use a metal spring clip. To adjust the water level, pinch both ends of the metal spring clip and raise or lower the float. Slide the float down on the actuating rod and then release the spring clip to lower the water level. To raise the water level, slide the float up on the rod and release the clip.

How to Adjust an Internal Float Fill Valve

Adjust an internal float fill valve by moving the entire head of the fill valve down. An internal float fill valve operates the same way as a float-cup fill valve but is a quieter valve with a more precise shut-off.

1. Twist the Top Head

   Twist the top head of the fill valve counterclockwise to unlock it.

2. Move the Valve Up or Down

   To lower the water level with this type of valve, move the entire head of the fill valve down. To raise the level of the water in the tank, raise the entire head of the fill valve up.

3. Twist the Top Head Back into Place

   Twist the head clockwise to lock it into place again. With the toilet lid still off, flush the toilet. Check the water level to make sure it stays 1 inch below the top of the overflow tube.

How to Adjust a Floatless or Pressure-Activated Fill Valve

True floatless fill valves use a pressure-sensing mechanism rather than a float to adjust the water level in the toilet tank. The valve operates underwater and can sense the water level based on pressure.

1. Turn the Adjustment Screw Clockwise or Counterclockwise

   Turn an adjustment screw located on the top of the valve. To raise the water level, turn the adjustment screw clockwise; to lower the water level, turn the screw counterclockwise.

2. Watch the Water Level

   The water level must be below the top of the tank's overflow tube. Continue adjusting until you get the desired water level.

Clear Mineral Deposits in Diaphragm Fill Valve

Older models of the diaphragm fill valve have a bonnet or cap made of cast brass like the rest of the fill valve body, though the button that moves the diaphragm is made of plastic. Calcium or other mineral deposits can build up between the brass bonnet and the plastic button, keeping the button in the closed position and preventing the water tank from refilling.

1. Spray penetrating oil into the top of the bonnet where the plastic button protrudes.
2. Work the button up and down by manually moving the float rod up and down.
3. The button should work free and the ballcock should then operate properly.