How to Adjust a Toilet Float? – A Detailed Guide

Written by

Paulk Webb


Freddie J. Hagopian

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how to adjust a toilet float

There can only be two reasons why you’re here: you can’t flush your waste because the water is not strong enough or you have a leaky toilet. You need to open the toilet tank’s lid because we will focus on the float.

This article will teach you how to adjust a toilet float in the fill valve to get adequate water in your tank. Doing so will allow you to maximize the use of your toilet, as well as avoid problems related to insufficient or excess water.

What is a Toilet Fill Valve?


Also called a “ballcock,” the fill valve is responsible for filling the tank with water for flushing.

This component also has a float, which determines the tank’s water level. For the toilet to function properly, we need to adjust the float that will make the water rest just 1 or 2 inches below the fill valve and overflow tube.

Floats may need occasional adjustments and here are some signs to know exactly when:


  • The toilet is not flushing completely.
  • The water leaks from the tank.
  • There is running water in the toilet bowl.

The next chapter contains step-by-step instructions on how to adjust the float on a toilet depending on the type, so you can fix and avoid the situations enumerated above.

Steps for Toilet Float Adjustment

It’s easy to tune up the float, but know that there are different toilet float types. Don’t worry, we will list all of them including their definitions and methods of adjustment.

1. Plunger or Piston-Type Ballcock


An old type of fill valve, the piston or plunger-type ballcock is made of brass and uses a plunger stem in controlling the entry of water. It has a rod attached to the top and at the end of that rod, there is a ball that floats.

The ball is important to this kind of fill valve. When we flush the toilet, the water goes out of the tank, and the ball float goes down as well. This opens the plunger stem and triggers the refill. Once there is enough water, the ball goes up again and the plunger closes.

How to adjust the float in a plunger or piston-type ballcock:

Step 1: Turn off the shut-off valve and flush the toilet to drain the tank.

Step 2: Check your tank if it has a mark indicating the recommended water level. Ideally, it should be 1 or 2 inches below the fill valve.

Tune the float to match this water measurement.

Step 3: To adjust the toilet float ball, we have to bend the rod. Bending it upward increases the water in the tank.


On the other hand, bending the rod downward lowers the water level.

Step 4: Open the shut-off valve to refill the tank. Observe the maximum water level reached after the float adjustment.

If it’s too high or low, continue to bend the rod until the ideal level is achieved.

2. Brass Diaphragm Ballcock

This fill valve is similar to the piston type; it’s made from brass and has a ball float at the end of the rod. The only difference is how they let the water in the tank since a brass diaphragm ballcock makes use of a diaphragm seal that is inside the valve’s round body.

When we flush, the ball float moves downward which causes the brass rod to press and add pressure to the diaphragm’s top, opening the water inlet for a refill. When there is enough water in the tank, the float ball goes upward which closes the water inlet.

How to adjust the float in a brass diaphragm ballcock:

1. Turn off the water supply then flush the toilet. Adjusting a toilet float will be easier with no water splashing around.

2. Bend the rod upwards for more water, and downwards for less.

The brass diaphragm ballcock is a fairly old fill valve model (second to the plunger type). Meaning, it usually still has no screw for tuning.

3. Turn on the water supply and check if the tank fills in at the correct water level, which is 1 or 2 inches below the fill valve and overflow tube.


3. Plastic Diaphragm Ballcock

What to Prepare: screwdriver (should match the adjustment screw’s head)

This looks and works the same as the brass diaphragm ballcock, except that it’s made of plastic and there is an adjustment screw located at the top of the fill valve. The plastic diaphragm ballcock is also commonly used in our toilets together with the float cup type.

How to adjust the float in a plastic diaphragm ballcock:

1. First, turn off the shut-off valve and flush the toilet. We don’t need to completely drain the tank.

2. To fix the float on a toilet, take the screwdriver and turn the adjustment screw clockwise to lower the water level, and counterclockwise to increase it.


3. Turn on the shut-off valve to refill the tank’s water, then check if the level is beneath the fill valve by 1 or 2 inches. If not, continue adjusting.

4. Float Cup Toilet Fill Valve

What to Prepare: screwdriver (should match the plastic screw mechanism’s head)

As mentioned, the float cup fill valve is a standard model that newer toilets often use. Instead of a rod with a float ball, it uses a cup that is attached to the fill valve’s shaft.

When we flush the toilet, the float cup goes down which opens the water inlet. Once the tank has enough water, the cup will go up which will close the inlet.

How to adjust the float in a float cup toilet fill valve:

1. Ensure that the water supply is shut off and flush the toilet to drain the tank.

2. To adjust a float-cup fill valve, use a screwdriver to turn the plastic screw mechanism counterclockwise to loosen the float cup.


If your float valve has a metal spring clip, pinch the ends before adjusting the cup as these clips serve as the lock.

3. Move the cup manually. If you lower the float in a toilet, that will lower the water level. If you slide it upwards, it will raise the level.

4. After adjusting, turn the screw clockwise to secure the float. If you’re pinching a spring clip, simply let go of the clip to lock the cup.

5. Turn on the water supply and check if the water refills at the correct level, which is 1 or 2 inches below the top of the fill valve.

5. Internal Float Fill Valve (QuietFill)

We can describe this fill valve as having a big and wide top since a smaller float is inside the head. An internal fill valve works like the float cup variant, but we can no longer see the up and down movement as the float is inside the valve itself.

It also received the name QuietFill because it works quieter than the other models, aside from being hidden.

How to adjust the float in an internal float fill valve:

1. As usual, turn off the shut-off valve and flush the toilet to remove the tank’s water. Although, we don’t have to completely drain it.

2. To tune an internal float, we need to twist the top of the valve’s head counterclockwise. This will unlock the valve, allowing us to move it.

3. This variation of fill valve allows us to change its height and that is also how we will adjust the amount of water in the tank.

Lower the entire head down to cut the water level, and raise the head to increase it.

4. Once you get the right height, twist the top head in a clockwise direction to lock the valve in place.


5. When you turn on the shut-off valve, observe if the height of the valve is optimal for getting the recommended water level which is 1 or 2 inches below the overflow tube.

6. Floatless Fill Valve (Activated by Pressure)

What to Prepare: Screwdriver, if necessary (should match the plastic screw mechanism’s head)

Commonly utilized by low-flow toilets, floatless fill valves will neither have a ball nor a cup. Instead, they use what we call the pressure-sensing diaphragm at the bottom of the tank or inside the fill valve.

How to adjust the float in a floatless fill valve:

1. Turn off the water supply and flush the toilet.

2. Check the adjustment screw of the valve. Sometimes, you can twist it manually. If not, use a screwdriver.


To lower the water level, turn the screw counterclockwise. To raise it, turn the screw clockwise.

3. Once you turn on the water supply, check where the water stops. It should be below the overflow tube by 1 or 2 inches.

Tips to Adjust a Float Like a Pro


  • Always check the type of your float before making any adjustments.
  • Inspect the water level before adjustment to know how much tuning you need to perform. Check for leaks at the back of the tank or in the bowl (the float is too high) or if you have a ridiculously weak flush (the float is too low).
  • Don’t forget to turn off the shut-off valve. Flushing the toilet to drain the tank also helps in tuning the float and avoids water from splashing.
  • When changing the height of the toilet float, it’s fine to make gradual adjustments until you achieve an accurate water level.
  • In every adjustment you make to the float, always test it by flushing the toilet. Observe how much water goes into the tank (if it’s enough) and check if there are problems with the other tank components.

Signs That You Need to Change a Toilet Float

Problems concerning the toilet can usually be fixed by checking the tank parts, such as checking if the fill valve has the correct height. However, there might be situations where the problems are still there despite the adjustments made.

  • If the toilet float is not shutting off the water despite lowering it, water will leak into the bowl. If simple repairs do not work in this case, you will need a new fill valve for the toilet to stop running.
  • If the tank is filling incredibly slowly, you may want to clean your fill valve by flushing off the debris. Also, check the water pressure if it’s strong enough and clean the water supply line. If these didn’t work, you may have to replace the component.
  • If you have an older diaphragm float that has a brass cap, mineral deposits may sit between this cap and the plastic button that operates the diaphragm. Essentially, this will cause water to stop running into the tank even when the float is down.

To solve this, we can spray penetrating oil at the top of the cap so the plastic button can move easily. Next, we should manually move the float rod up and down to warm up the button. However, if this doesn’t work, we may have to replace the fill valve completely.


To answer the question of how to adjust a toilet float, we first have to determine what kind of fill valve our toilet is using.

Plunger or piston-type and brass diaphragm ballcocks are adjusted by bending their rods. Plastic diaphragm, floatless, and float cup fill valves have adjustment screws that you must turn clockwise or counterclockwise—according to instructions—to change the water level.

Although for float cups, they can have spring clips instead that you have to press and let go. Lastly, internal float valves have adjustable heads that you have to twist to lower or raise the entire fill valve.

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