How to Adjust Water Level in Toilet Tank

All residential toilets have several working components inside the toilet tank but there are only two valves at work each time you pull the flush lever. The first one is the flush valve which releases the water that is stored within the toilet tank. The second one is the fill valve or, traditionally, the ballcock. The fill valve controls the flow of water as it refills the toilet tank.

It’s rare that you will ever need to adjust the toilet bowl water level or the water level inside the toilet tank. It’s important to keep a correct water level in your toilet or else it could lead to overflowing or a low water level, both of which could cause further issues. 

       Occasionally, either the flush valve or the fill valve will need attention. While it is uncommon to have to make adjustments to the toilet’s fill valve, it is, thankfully, an easy at-home project. There are many different types of fill valves and each one has a different method meant for that specific fill valve for adjusting the water level. Be sure to check what brand and type of fill valve you have before making adjustments. 

Materials Needed:

• Screwdriver 
• Penetrating Oil as needed

Note: Penetrating Oil is for older toilets or diaphragm fill valves that have a bonnet, or a cap made out of cast brass. If you have hard water, calcium or mineral deposits from the water can build up between the bonnet and the plastic button. This creates friction that then causes the plastic button to remain in the “closed” position. In order to fix this, you’ll need penetrating oil.

How To Adjust Water Level in Toilet Tank

How to adjust a Piston or Plunger style fill valve – Brass:

       Note: These types of fill valves consist of a floating ball attached to a horizontal brass floating rod. The brass rod moves up and down to raise and lower the plunger or piston. This starts and stops the flow of water to the toilet tank. This style of fill valve is now mostly uncommon and is not found in newer toilets. 

1. Gently bend the float rod upwards to increase the flow of water and the water fill level inside the toilet tank. If you need a lower water level, bend the float rod downwards.
2. Pull down on the flush lever, flushing the water out of the toilet tank. Watch the toilet bowl water level as well as the toilet tank water level to ensure that you have proper levels.
3.  If you have a lower water level than desired, bend the float road downwards until you reach the correct water level. If you have a higher water level, bend the float rod downwards until you reach the correct water level.

Adjusting a Diaphragm Ballcock – Brass:

       Note: The brass diaphragm ballcock is similar to the plunger/piston style except the fill valve itself does not use the plunger stem. Instead, it has a diaphragm seal that is found inside a round fill valve body. This style also has a float rod and ball to control the water level.

1. Gently bend the float rod upwards to increase the flow of water and the water fill level inside the toilet tank. If you need a lower water level, bend the float rod downwards.
2. You need to watch the water level. Flush the toilet once and watch as the fill valve fills the tank. The rising water level has to be below the top of the overflow tube. Continue to make small adjustments until you have reached the correct water level.

Adjusting a Diaphragm Ballcock – Plastic:

Note: In the plastic version of the diaphragm ballcock, the lever assembly moves the plastic button located at the top of the bonnet. This presses against a rubber or plastic diaphragm to control the flow of water into the toilet tank. In newer versions of the plastic diaphragms, there is an adjustment screw located on top that allows you to adjust the height of the ballcock without needing to bend any of the pieces.

1. Check the screw head that is located at the top of the fill valve. Determine if you will need a flathead or a Phillips head screwdriver. Using the screwdriver, twist the screw counterclockwise to raise the water level or twist the screw clockwise for a lower water level.
2. You need to watch the water level. Flush the toilet once and watch as the fill valve fills the tank. The rising water level has to be below the top of the overflow tube. Continue to make small adjustments until you have reached the correct water level.

Adjusting a Float Cup Fill Valve

Note: The Float Cup Fill Valve style is the most current standard design of the fill valve used in most single flushing toilets. The water flow is controlled by the cylinder plastic float that moves up and down along the fill valve shaft. This style does not use a float device. The floating cup is attached to the fill valve by a plastic screw or a metal spring clip, clipped to a metal rod.

1. On some styles of float cup valves, there is a plastic screw that if turned, will create a higher water level or a lower water level. Locate the screw and have a screwdriver on hand. 

2. If you need a higher water level in the toilet tank, slide the float upwards on the rod. If you need a lower water level in the toilet tank, slide the float downwards on the rod. Twist the screw to tighten the float cup in place. 

3. You need to watch the water level. Flush the toilet once and watch as the fill valve fills the tank. The rising water level has to be below the top of the overflow tube. Continue to make small adjustments until you have reached the correct water level.

4. Optional: If your style of float cup uses a metal spring clip, you’ll need to pinch both ends of the clip to raise or lower the float. Slide the float downwards on the rod and release the spring clip to have a lower water level. To have a higher water level, slide the float upwards and release the spring clip.

Adjusting an Internal Float Fill Valve

       Note: The Internal Float Fill Valve is a newer style of the fill valve. It is often marketed as the Quiet Fill. It has an internal float lever inside the head of the fill valve that is hidden from your view. It works the same way as a Float Cup Fill Valve.

1. To unlock the fill valve, twist the top of the head counterclockwise. 
2. If you need a lower water level, you’ll need to move the entire head downwards. If you need a higher water level, you’ll need to move the head of the fill valve upwards.
3. To lock the head of the fill valve back into place, simply turn it clockwise. 
4. Flush the toilet once and watch as the toilet tank fills up. Check the bowl water level as well as the tank water level. Adjust as needed. 

Adjusting a Floatless/Pressure-Activated Fill Valve

       Note: Floatless Fill Valves use a pressure sensor inside the machine instead of a float ball to adjust the water level in your toilet. This fill valve works underwater and senses the water level based on the pressure inside the toilet tank.

1. Located at the top of the fill valve is an adjustment screw. Locate the screw and determine if you will need a flathead screwdriver or a Phillips head screwdriver. 
2. For a lower water level, twist the screw counterclockwise. For a higher water level, twist the screw counterclockwise.
3. You need to watch the water level. Flush the toilet once and watch as the fill valve fills the tank. The rising water level has to be below the top of the overflow tube. Continue to make small adjustments until you have reached the correct water level.

For Tanks that Won’t Refill 

       For older versions of the diaphragm fill valves that are made out of brass come the problem of calcium or mineral deposits from hard water. The buildup can happen between the brass bonnet and the plastic button on the fill valve thus creating friction. This causes the button to become stuck in the “closed” position even if the float rod and ball have dropped back into the tank. You’ll know this has happened if the toilet bowl is empty and the toilet tank is not refilling properly. 

1. Locate where the plastic button and the brass bonnet meet in the fill valve. 
2. Spray penetrating oil into the area where the two components meet. 
3. Manually move the float rod up and down to work the oil into the mechanism. 
4. Continue to do so, adding small sprays of the penetrating oil until the button works its way free. The ballcock should begin to work properly and begin filling the toilet tank to the correct water level.
5. Pull down on the flush lever once and allow water to cycle through your toilet. The fill valve should begin filling the toilet tank on its own. 

       Additionally, if you find that you have little to no water pressure when the toilet tank is filling, check the water supply line. Ensure that the water supply line is operating correctly and has full water pressure going through the line into the toilet tank. 

Turn the knob or lever that controls the water pressure in the water supply line clockwise to ensure that the water valve is completely open. Be sure to also inspect the water supply line for any leaks. Inspect the plastic nuts that connect the water supply line to the valve and the toilet tank. If you find that these areas are leaking, you will need to begin a different toilet repair project.