How to Stop a Constantly Running Toilet by Adjusting the Fill Valve Float
About This Project
This guide provides step-by-step instructions for diagnosing and fixing a constantly running toilet by adjusting the fill valve float. The process involves removing the tank lid, identifying the water level and float type, making precise adjustments to the float mechanism to lower the water level, and testing the repair to ensure the toilet functions correctly without running continuously.
Best for beginners and first-time DIYers with basic plumbing knowledge.
Tools & Materials
Towel
Panther Vision FLATEYE F-310 High Performance 310-Lumen Unround Flashlight CREE LED Multi Position Waterproof and Shockproof FL-6960
Screwdriver (Multi)
Water
NITECORE 4000 Lumens USB-C LED Rechargeable Tactical Flashlight P20iX
KOHLER Toilet Tank Cover in White 1086929-0
Towel
Absorbs moisture and dries surfaces.
Panther Vision FLATEYE F-310 High Performance 310-Lumen Unround Flashlight CREE LED Multi Position Waterproof and Shockproof FL-6960
Every revolution starts with a spark. At 310-Lumens the F-310 has the power to ignite our un-round revolution without overpowering your needs or your wallet. Not your granddads flashlight these bad boys
Screwdriver (Multi)
Multiple bits for versatile use.
Water
Essential for life and countless tasks.
NITECORE 4000 Lumens USB-C LED Rechargeable Tactical Flashlight P20iX
The NITECORE P20iX is unrivaled when it comes to performance. NITECORE took the beloved P20i frame and maintained the compact size, ergonomics and doubled the power with 4 LEDs. This Xtreme high lumen
KOHLER Toilet Tank Cover in White 1086929-0
This toilet tank cover is constructed of vitreous china. It has a white finish. It has a one-year limited warranty.
Steps
Remove the Tank Lid
1 minBegin by carefully lifting the ceramic lid off the top of the toilet tank. Since these lids are heavy and fragile, use both hands. Place the lid on a secure, flat surface out of the way, such as on a towel on the bathroom floor, to prevent it from being knocked over or cracked.
Watch: Attach Tank to Bowl
Inspect Water Level and Identify Float
2 minsLook inside the tank to identify the cause of the running water. You will see a tall, vertical tube in the center; this is the overflow tube. Observe the water level. If it is high enough to be constantly spilling into the top of the overflow tube, the fill valve float is set too high. Also, identify your float type. Based on our assumed answer, you are looking for a 'float cup,' which is a cylindrical cup that wraps around the main shaft of the fill valve assembly (usually located on the left side of the tank).
Watch: Reinstall Float and Test
Adjust the Float Cup
3 minsTo lower the water level, you must adjust the float cup downwards. Look for the adjustment mechanism on the fill valve. Most modern float cups have one of two adjustment types. The first is a long plastic adjustment screw that runs parallel to the fill valve; use a screwdriver or your fingers to turn this screw. Turning it counter-clockwise typically lowers the float. The second type is a spring-loaded clip; you'll need to squeeze the clip and then manually slide the entire float cup down the fill valve shaft. Lower the float by about a half-inch to start.
Watch: Adjusting a Standard Fill Valve
Test the Adjustment
5 minsAfter making an initial adjustment, you must test the new water level. Flush the toilet by pressing the handle. Allow the tank to completely refill with water. Watch the water level as it rises. The fill valve should now shut off completely when the water level is approximately 1/2 to 1 inch below the top of the overflow tube. If the water still rises too high and enters the tube, repeat Step 3 to lower the float a little more. If the water level is now too low, resulting in a weak flush, adjust the float slightly higher. Repeat this test until the water shuts off at the correct level.
Watch: Test the New Flapper
Replace Tank Lid
1 minOnce you have confirmed that the toilet flushes properly and the water shuts off at the correct level without running, the repair is complete. Carefully pick up the porcelain tank lid and place it back onto the top of the toilet tank, ensuring it sits squarely and securely in place.
Watch: Test the ToiletCommon Problems
Toilet uses too much water per flush, leading to high water bills.
Solution: If your new flapper has adjustable openings, you can rotate the dial to control how long the flapper stays open, thereby adjusting the amount of water used per flush.
Cracked fill valve cap from over-tightening.
Solution: The cap should be hand-tight. If it is difficult to turn, try using a cloth for better grip, but avoid using tools that could crack the plastic.
Do not raise the float so high that the water level will exceed the height of the overflow pipe.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Toilet won't shut off because water bypasses the overflow tube.
Solution: Ensure the fill tube is positioned to spray water directly down into the overflow tube, not just into the tank.
Toilet water level too high or too low, causing continuous running.
Solution: Turning the nut clockwise raises the water level; turning it counter-clockwise lowers it.
The components are plastic, so do not use tools or excessive force to turn the adjustment nut.
Solution: To avoid this issue: Be mindful of this warning and take appropriate precautions.
Toilet water level is too high, causing overflow or constant running.
Solution: You may need to make small adjustments to get the water level just right. The video shows a final fine-tuning by pressing the adjustment clip/screw on top of the float.
Frequently Asked Questions
What specific tools will I need to adjust the fill valve float?
For most modern fill valve adjustments, you typically won't need specialized tools beyond your hands. Some older or specific fill valve types might require a flathead or Phillips screwdriver to loosen a lock screw or a pair of pliers to gently turn a locking nut. Always have a towel handy for any minor spills.
Do I need to turn off the water supply to the toilet before adjusting the float?
While not strictly necessary for simply adjusting the float, it's a recommended safety measure, especially for beginners. Turning off the water at the shut-off valve behind the toilet prevents accidental overflows if you inadvertently displace a component. Remember to turn the water back on fully after testing your adjustment.
How do I know if I've adjusted the float to the correct water level?
The ideal water level is typically about 1 inch below the top of the overflow tube in the tank. After each adjustment, flush the toilet and observe the water refilling. The fill valve should shut off completely once the water reaches this level, and the toilet should remain silent without any trickling sound.
What should I do if adjusting the float doesn't stop the toilet from running?
If adjusting the float doesn't resolve the constant running, the problem likely lies elsewhere in the fill valve assembly or with the flapper valve at the bottom of the tank. The flapper might not be sealing properly, or the fill valve itself could be faulty and require replacement. Consider checking the flapper for wear or obstruction next.
My toilet has a different type of float than a float cup. Can I still follow these steps?
While the principle is the same—lowering the water level to prevent overfilling—the adjustment method varies by float type. If you have a ball float, you'd typically bend the float arm slightly. If it's a cylindrical float on a vertical rod, you would usually slide a clip or turn a screw on the rod to change its position. Identify your specific float type and look for its unique adjustment mechanism.
How can I tell if the running water is coming from the fill valve (float) or the flapper valve at the bottom of the tank?
To diagnose the source, add a few drops of food coloring to the tank water (without flushing). Wait about 15-20 minutes. If the color appears in the toilet bowl without flushing, the flapper valve is leaking. If the tank keeps refilling with fresh water or you hear a continuous hiss, the fill valve (float) is likely the issue.
