How to Adjust a Toilet Ball Float to Stop Overfilling

Why the ball float matters

The ball float is a common part on older toilet fill valves. It is a hollow ball attached to an arm, and it rises and falls with the water in the tank. When the tank is full, the float presses the arm against the fill valve mechanism and shuts off the water. If that set point is too high, the tank fills past its normal level and water spills into the overflow tube. The fill valve keeps trying to top off the tank, so the toilet runs on its own.

A running toilet is more than an annoyance. Toilets are the main source of indoor water use in a typical home, accounting for nearly 30 percent of indoor consumption, according to the EPA. Household leaks can waste 180 gallons per week, and toilets are often the culprit. Adjusting the float is one of the first steps to stop the wasted water before you consider a larger repair.

How a ball float and fill valve work together

Older fill valves use a ball that floats on the surface of the tank water. The ball is threaded onto a metal or plastic arm, and that arm connects to the fill valve body. After a flush, water enters the tank and the ball rises with the water level. At the correct height, the arm pushes a plunger or diaphragm inside the valve and stops the flow.

The target water level is just below the top of the overflow tube, not the very top of the tank. If the float is set too low, the tank holds less water and the flush can feel weak. If it is set too high, the water reaches the overflow tube before the valve closes, and the excess runs down into the bowl. For a closer look at the parts involved, see the toilet parts guide and the tank water level explainer.

Before you adjust

Start by turning off the water supply valve on the wall or floor behind the toilet. Then remove the tank lid and set it aside on a flat surface. Flush the toilet and watch the refill cycle. The water level after the flush is what you are adjusting, not the height of the float ball in a full tank.

Check the float ball before you change its position. If the ball has a crack or has taken on water, it will sit lower no matter how you set the arm. In that case, adjusting the arm will not work reliably and you should replace the tank float. Also confirm that the overflow tube is clear and that the fill valve body is secure.

• Shut off the water supply.
• Remove the tank lid.
• Flush and watch the refill.
• Inspect the float ball for cracks or water inside.
• Check that the overflow tube is clear.

Adjusting a metal arm ball float

The simplest older design has a metal rod with a threaded ball on the end. To lower the tank water level, gently bend the rod downward near the fill valve. This makes the ball sit lower in the tank before it closes the valve, so the water stops at a lower point. To raise the water level, bend the rod upward. Use small adjustments and avoid kinking the rod or forcing it against the valve body. Some metal arm designs use an adjustment screw on the valve body instead; turning that screw does the same job.

After each small bend, flush the toilet and let the tank refill. Most toilets reach the right setting after one or two tries. Aim for the water line to sit about an inch below the top of the overflow tube. If the water stops below that, the fill valve should close cleanly. If the valve still hisses or runs, see how to fix a running toilet for the next steps.

When you bend the arm, only the arm should move. If the fill valve body shifts or the mounting nut loosens, tighten it before testing. A wobbly fill valve can allow water to escape around the base of the tank.

Adjusting a plastic ball-float valve

Newer float-type fill valves use a plastic float rather than a large metal ball, but the principle is the same. The float may ride on a stem beside the valve, and the arm is often part of the float assembly. Look for an adjustment screw on top of the valve or a clip that holds the float to the rod.

Turn the screw one way or the other to move the shutoff point, or slide the clip and float up or down. After each adjustment, flush and check the new water level. The same target applies: about an inch below the top of the overflow tube. If the plastic float is cracked or full of water, replace it instead of adjusting.

Some of these valves have an overall height adjustment as well. If moving the float does not give enough range, see how to adjust the fill valve height. A fill valve that is too tall for the tank can also keep the water level high.

Test the toilet and know when to replace

After the float adjustment, run the toilet through several full flushes. Listen for water running after the tank refills and for a hissing sound from the fill valve. You can also do a simple dye test: place a few drops of food coloring in the tank, wait without flushing, and check whether color appears in the bowl. If it does, the flapper is leaking rather than the float. For that repair, see how to replace a toilet flapper.

If the toilet still runs, the fill valve may be worn, the float may be waterlogged, or the problem may be in the flush valve below the tank. Work through the causes with the toilet running water causes guide before buying parts.

If your toilet is old and inefficient, a successful float adjustment is a good short-term fix, but a replacement can be better over time. The EPA notes that older toilets can use as much as 6 gallons per flush, while WaterSense labeled models use 1.28 gallons per flush or less, which is 20 percent less than the 1.6 gallon federal standard. Replacing an old toilet with a WaterSense labeled model can reduce water used for toilets by 20 to 60 percent. To compare models, see the best 1.28 GPF toilets and best dual flush toilets guides.

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Questions

Why does my toilet keep overfilling after I adjust the float?

The float ball may be waterlogged, the arm may be worn, or the fill valve may no longer close completely. Check whether the ball floats by removing it and shaking it for water inside. Replace the float if needed, or see how to replace a toilet fill valve if the valve itself is the problem.

How do I lower the water level in the tank?

Lower the float's shutoff point. On a metal arm ball float, bend the arm down slightly. On a plastic ball-float valve, turn the adjustment screw or slide the clip down. The water should stop about an inch below the top of the overflow tube. Flush and repeat until the valve shuts off cleanly.

Can the ball float itself make a toilet run constantly?

Yes. If the float is set too high, water reaches the overflow tube before the valve closes, so the tank keeps receiving water. If the float leaks and fills with water, it cannot rise enough to close the valve. Both situations cause a continuously running toilet.

What is the difference between a ball float and a flapper?

The ball float controls when the fill valve stops adding water to the tank. The flapper is the seal at the bottom of the tank that releases water into the bowl during a flush. A toilet can run because of either part. See flapper vs tower flush valve for more.

Does adjusting the ball float save water?

It can stop wasted water from a running toilet. The EPA says household leaks can waste 180 gallons per week, and toilets are often the culprit. Over the long term, replacing an older toilet that uses up to 6 gallons per flush with a WaterSense labeled model that uses 1.28 gallons or less saves far more.