How to Adjust the Water Level in Toilet Bowl

Adjusting a Ball-and-Arm Float

Remove the toilet tank lid. Lift the lid off of the tank and set it aside on a flat, stable surface. You’ll now have access to the flushing mechanisms inside the tank. Be careful not to drop the lid or set it somewhere from which it might fall. Toilet tank lids are made of ceramic and can break fairly easily.

Take note of the water level inside the tank. The water in the tank should rest 1–2 inches (2.5–5.1 cm) below the fill valve and overflow tube (the large open pipe near the center of the tank). If it seems higher or lower than this level, your water level may be off-balance. Your toilet may also have a line in its tank, either printed on or etched in porcelain, that shows you where the water level should be.

Turn off the water supply to the toilet. Locate the external water valve on the wall behind and beneath the toilet. Rotate the oblong knob clockwise as far as it will go, then flush the toilet. After it flushes, the tank will not refill itself. This will allow you to work inside the tank unobstructed. Keep turning the knob until you hear the water stop running. Do not attempt to adjust or repair any of the mechanisms inside the toilet tank without emptying it first.

Examine the float and fill valve. Look over the flushing mechanisms to see what kind of condition they’re in. If you notice any obvious damage or defects, you might need to call a professional to have the part repaired.

Examine the toilet tank's float height. Check the toilet tank’s float, a plastic ball attached to a long arm at the top of the fill valve. The height of the float determines how much water remains in the tank after it refills. It should be at the water level if it is not broken. If the float appears too high or low, adjust the float height and when you refill the tank, check how it changes the water level. If it is above or below the water level, this may be the source of your high/low water level. Give the float a shake. If you can hear water inside of it, you should have a plumber replace it. Make sure the float is properly connected to the fill valve.

Use a screwdriver to raise or lower the float height. Directly on top of the fill valve should be a single screw. Turn this screw clockwise or counterclockwise 1 full rotation. Clockwise will raise the water level and counterclockwise will lower it. Avoid turning the screw more than 1 full rotation at a time. Doing too large of an adjustment at once could cause the toilet to flush inconsistently. If the screw is too rusty to turn, you can adjust the float by simply turning it. It is threaded to the metal rod the connects directly to the fill valve.

Flush the toilet to test the water level. Turn the water to the toilet back on and give the tank a minute or 2 to fill up. After you’ve flushed the toilet, observe the water level in the bowl. Ideally, the bowl should be about halfway full. If the water in the bowl still looks too high or low, empty the tank and try adjusting the float again until you get it right. Call a plumber if the water level is still off after adjusting the float several times.

Adjusting a Cylinder Float

Identify the cylinder float. Some newer toilets are equipped with more modern one-piece floats (also sometimes known as “floating cups”) instead of the older ball-and-arm design. These types of floats have been engineered as solid cylinders fitted to the shaft of the fill valve itself. If you have a fill valve with a cylinder float, you can adjust the water level in your toilet in just a few seconds. Cylinder valves are easy to install, remove and perform maintenance on, and more user-friendly for individuals less experienced with home repairs.

Lift off the toilet tank lid. Remove the lid from the tank and set it aside on a flat surface, like a table. Be careful not to drop the lid or set it near the edge of a surface, as most toilet lids are ceramic and break easily. After the toilet lid is removed, check the water level—if it seems higher or lower than 1–2 inches (2.5–5.1 cm) below the fill valve and overflow tube, it may need adjustments.

Turn off the water supply before you work on the float. Locate the external water valve on the wall—it should be behind your toilet, beneath the bowl. Rotate the knob clockwise as far as it will go. When it won't go any farther, flush the toilet and continue flushing until the tank is empty.

Locate the adjustment stem on the side of the float. The adjustment stem is a long, slender tube that connects to the larger fill valve. In most models, it will either run parallel with the valve or extend horizontally out from the top. The adjustment stem is used to increase or decrease the amount of water in the tank. Familiarize yourself with the mechanisms inside your toilet tank before making any drastic changes. Refer to the instruction manual or manufacturer's website if available.

Check for a release clip on the float. Some cylinder floats can be positioned by squeezing a release clip on the float itself and raising or lowering it to the desired height. Raising the dial will raise the water level, and lowering it should lower the water level. If your float has a release clip, squeeze it to adjust it to the desired height. If not, however, you will need to locate the toilet's adjustment dial.

Raise or lower the float ⁄2 inch (1.3 cm). Use 2 fingers to grasp the notched dial on the end of the stem. Twist the stem clockwise or counterclockwise a full rotation—clockwise to lower the height or counterclockwise to raise it. Once you’ve found a suitable height for the float, replace the toilet lid and turn the water valve back on. If you’re having trouble turning the adjustment stem, check for a screwdriver notch. Some adjustment dials are secured by screws. Do not turn the notch more than 1 full rotation at a time. If your toilet water level is adjusted too suddenly, it can cause inconsistent flushing.

Test the toilet level height after you have turned the water valve on. Flush the toilet a couple of times to check whether the water level in the bowl has lowered or risen. The bowl should be about halfway full. If not, continue fine-tuning the float until you reach your desired height. Call a plumber if, after several adjustments, the level still seems off.

Installing a New Fill Valve

Replace the fill valve if adjustments don't seem to help. If your toilet runs constantly and changing the float's height doesn't help, you may need to replace the fill valve. Replacing a fill valve involves opening the hole at the base of the tank—if you do not feel comfortable working this extensively with your toilet, you may need to call a plumber. The fill valve you need may vary depending on the kind of toilet you have. Check what kind of fill valve your toilet model needs online before buying one. You can also buy a universal toilet repair kit at a hardware or department store. It comes with a new fill valve, float, and flapper that fit almost every toilet.

Shut off the water supply and drain the toilet bowl. To install the replacement valve, the toilet tank needs to be completely empty. Locate the external water valve on the wall behind and beneath the toilet. Rotate the knob clockwise until it will not go any further, then flush the toilet. After it flushes, the tank won't refill itself. Continue flushing the tank until the water is completely emptied. Sop up any residual water in the tank with a sponge or towel.

Detach the fill valve from the outside of the toilet tank. You should see 2 nuts on the outside of the tank. First, unscrew the one that connects the water supply line to the valve. Pull the supply line out of the valve. Then, unscrew the plastic nut that secures the fill valve to the tank, which should be easy to loosen. With both nuts unscrewed, the fill valve should come right out. You may need to use a wrench or pair of pliers to loosen the nut. Lay down a towel in case any residual water leaks out of the detached water supply hose.

Lift the old valve out of the tank. Extract the entire fill valve unit, including the attached float. The unit should simply come out in 1 piece. Discard the old valve unless you plan to have it repaired by a professional later. Work carefully to avoid damaging or dislodging any of the other mechanisms inside the tank.

Slide the new fill valve into place. Fit the bottom portion of the valve through the hole in the base of the tank. The rest of the unit should sit upright once the fill valve is in place, and it should feel secure—no wobbling or moving around. Make sure it's attached to the base before putting the the toilet back together.

Reattach the water supply hose. Attach the hose back to the bottom of the valve, and slide back on any washers connecting the small water supply hose to the base of the toilet tank. Screw the large nut back on tightly to prevent leakages when you turn the water supply on again.

Turn the water supply back on and give the toilet a test flush. Locate the external water valve again on the wall behind the toilet and rotate it clockwise to turn on the water supply. Flush the toilet several times to test the water and check its new level. You should also check the water shut-off valve and the bottom of the new fill valve. Wipe these areas with a tissue to check for moisture, and tighten the connections again if you find any. If the level still seems off, call a professional. A plumber may be able to troubleshoot your problem and solve the issue.