How to Replace a Toilet Tank Float

Tools and preparation

Before you start, gather a few basic tools: an adjustable wrench, a screwdriver, a bucket, and a towel. You also need a replacement float or, for a fill valve, a complete fill valve kit. Most hardware stores carry these parts in standard sizes.

Begin by turning off the water supply valve, usually located on the wall or floor beneath the toilet. Then, flush to drain most of the water from the tank. Use a bucket and towel to soak up the remaining water. Mark the water level with a pencil before removing anything so you have a reference for adjustment.

If the tank still has water after flushing, press down on the flapper or use a sponge to remove the residue. Keeping the tank dry makes the job cleaner and prevents parts from slipping.

• Adjustable wrench or pliers
• Screwdriver (flathead or Phillips, depending on the fasteners)
• Bucket and towel
• Replacement float or fill valve

Identify the float type

Toilets use two common float mechanisms. Older toilets have a ballcock with a hollow float ball mounted on a horizontal arm. When the tank fills, the ball rises and pushes the arm to close the valve. Newer toilets use a fill valve with a cylindrical float that slides up and down along the valve body, often called a float cup or float collar.

To see which type you have, remove the tank lid and look at the top of the fill valve. If you see a shiny metal or plastic ball at the end of a long rod, it is a ballcock. If you see a tube with a black or white collar that slides along it, it is a fill valve with an integrated float. For a detailed breakdown of the components, see toilet parts explained.

Some fill valves use a diaphragm or piston inside, but the float is always part of the assembly. Therefore, when the float fails, you usually replace the entire fill valve rather than just the float. For a ballcock, you can often replace only the float ball or the arm assembly.

Replace the float on a ballcock

If your toilet has a ballcock, the float ball is attached to a metal or plastic arm with a threaded stud. To remove it, grip the arm firmly with pliers and unscrew the float ball counterclockwise. If the stud is corroded or frozen, spray it with a penetrating oil and wait a few minutes.

After removing the old float, clean the threads on the arm and apply a little pipe sealant or Teflon tape to prevent leaks. Screw the new float ball on clockwise until it is snug, but do not overtighten. Hand-tight is usually sufficient.

If the arm itself is bent or the ballcock mechanism is worn, replacement of the entire ballcock may be more effective. In that case, follow the steps for replacing a fill valve, as the procedure is similar. See also how to replace a toilet fill valve for more details.

Replace the fill valve with a new float

For modern fill valves, the float is not sold separately. You must replace the whole fill valve. Start by turning off the water supply and flushing the toilet. Disconnect the supply line from the bottom of the fill valve using a wrench. Place a bucket underneath to catch any water.

Loosen the large locknut on the underside of the tank that holds the fill valve in place. Some valves have a retaining ring or clip. Lift the old fill valve straight up and out of the tank. Clean the hole in the tank and the surrounding area.

Insert the new fill valve through the hole, making sure the rubber washer is on the inside or outside as specified. Adjust the height so the top of the valve sits about one inch above the overflow tube, or per the manufacturer’s instructions. Tighten the locknut from underneath, but do not overtighten.

Reconnect the supply line to the fill valve bottom. Also connect the refill tube (a small hose that clips to the overflow tube) to the appropriate fitting. Turn on the water supply and let the tank fill. Check for leaks around the valve base and the supply line connection. If you are also replacing the flush valve, refer to our guide on toilet flush valve sizes.

Adjust the float for the correct water level

After replacing the float, the water level should be set correctly. Most tanks have a water level mark on the overflow tube, usually about an inch below the top. If the water level is too high, it may spill into the overflow tube and cause a constant running toilet. Too low, and the flush may be weak.

For a ballcock, you can adjust the water level by bending the float arm down slightly to lower the water level, or up to raise it. A slight bend is usually enough. Be careful not to break the arm.

For a fill valve with a float cup, there is typically a screw or a clip on the side. Turn the screw clockwise to lower the water level, counterclockwise to raise it. Some models use a locking clip; slide the float up or down to adjust, then lock it in place. For more on water levels, see toilet tank water level.

After adjusting, flush the toilet and watch the tank fill. Re-check the water level after the fill stops. Adjust again if needed. A properly adjusted float stops water at the mark, not touching the overflow tube.

Troubleshoot after replacement

If the toilet continues to run after replacing the float, check three points: the flapper, the refill tube, and the fill valve closure. A common cause is a worn flapper; see our flapper replacement guide. The flapper may be old and warped; replace it if it does not seal. The refill tube should be aimed into the overflow tube, not down into the tank. If the fill valve does not shut off fully, adjust the float down a little more.

A weak flush after replacement usually means the water level is set too low. Raise the float so the tank holds more water, but keep it below the overflow tube. Also check the flush valve chain: it should have a little slack, but not so much that it prevents the flapper from lifting fully.

If you hear hissing or humming, the fill valve may have a damaged washer or diaphragm. Sometimes simply cleaning the valve seat solves the problem. If not, replace the entire fill valve.

Remember that a running toilet can waste a significant amount of water, as the EPA notes that toilet leaks are often the cause of household water waste, and a worn flapper is a common culprit. Replacing the float is a simple fix, but regular maintenance of the flapper and fill valve keeps your toilet working efficiently. For a full troubleshooting approach, visit how to fix a running toilet.

What to pick for your next toilet

Questions

How do I know if my toilet float is broken?

A broken float often causes the water to run continuously because the fill valve does not shut off. You may also hear a hissing sound, or the tank may not fill to the proper level. Inspect the float for cracks, water inside, or a bent arm.

Can I replace just the float on a modern fill valve?

On most modern fill valves, the float is integrated with the valve body and cannot be purchased separately. You need to replace the entire fill valve. On older ballcocks, the float ball is a separate part and can be replaced individually.

Why does my toilet run after replacing the float?

Check the float adjustment. If the water level is too high, it may spill into the overflow tube. Also inspect the flapper: a warped or dirty flapper may not seat properly. Make sure the refill tube is positioned correctly and not interfering with the flapper. For more on flapper issues, see why my flapper won't seal.

How do I set the correct water level in the tank?

Most toilets have a water level mark on the overflow tube, usually about one inch below the top. Adjust the float so the water stops at that mark. For ballcocks, bend the float arm slightly; for fill valves, turn the adjustment screw or slide the float cup.

Is replacing the float a job I can do myself?

Yes, it is a straightforward repair that requires basic hand tools. Turn off the water supply, empty the tank, and follow the steps. If you are uncomfortable, you can hire a plumber, but many homeowners can handle it in under an hour. See our toilet parts maintenance schedule for regular upkeep.

What if my toilet is very old and still leaks?

If the tank and bowl are in good condition, replacing the float, flapper, and fill valve can extend its life. However, if your toilet is from the 1990s or earlier and uses more than 1.6 gallons per flush, replacing it with a WaterSense labeled model can save water and reduce future repairs. Check our best 1.28 GPF toilets for options.