A running Kohler toilet isn’t just an annoying disturbance—it’s a costly problem. The continuous cycling of water not only wastes valuable resources but can add hundreds of dollars to your water bill if left unchecked. Despite Kohler’s reputation for high-quality plumbing fixtures, even their toilets can develop issues like worn-out flappers, malfunctioning fill valves, or misaligned float mechanisms.
In this guide, we’ll walk you through what causes a Kohler toilet to keep running, and more importantly, how to fix it using simple, step-by-step methods. Whether you’re a DIYer or a homeowner seeking answers, this comprehensive tutorial will save you time, water, and money.
Why Is Your Kohler Toilet Running Constantly?
Before diving into the fixes, let’s understand how a Kohler toilet works and why it might be running.
Basic Toilet Mechanism
A standard Kohler toilet operates similarly to other gravity-fed toilets. When you flush:
- The trip lever lifts the chain connected to the flapper.
- The flapper lifts, allowing water to rush from the tank to the bowl.
- After flushing, the flapper drops back down, sealing the flush valve.
- The fill valve refills the tank until the water level reaches the preset height.
- The float (either a rod or cup) rises with the water and shuts off the fill valve when it reaches the ideal level.
If any of these components malfunction, your toilet may continue running indefinitely.
Common Causes of a Running Kohler Toilet
Here are the primary culprits behind a constantly running toilet:
- Worn-out or warped flapper that doesn’t seal properly.
- Improperly adjusted or broken chain connected to the flapper.
- Faulty fill valve that keeps the water flowing.
- Overflow tube leaks due to excessive water levels.
- Damaged flush valve assembly.
- Misaligned or stuck float mechanism.
- Loose tank-to-bowl gasket causing internal leaks.
How to Fix a Running Kohler Toilet: 7 Effective Methods
Below are 7 step-by-step techniques to diagnose and repair your Kohler toilet issue. You don’t need to be a plumber—just follow these instructions and use some basic tools.
Method 1: Inspect and Adjust the Fill Valve
The fill valve controls the water entering the tank. If the water level is too high, it may continuously overflow into the overflow tube.
Step-by-step:
- Remove the toilet tank lid.
- Observe the water level. It should be about 1 inch below the top of the overflow tube.
- If water is flowing into the tube constantly, the fill valve needs adjustment.
- Most Kohler toilets have a screw on the valve’s top—use a screwdriver or pliers to turn it clockwise to lower the float.
- Flush the toilet and observe if the new water level remains below the overflow tube.
This simple tweak often fixes constant running issues.
Method 2: Replace the Water Inlet Isolation Valve
If your fill valve isn’t working after adjustment, the water supply valve might be faulty.
Step-by-step:
- Turn off the water supply at the shutoff valve (usually behind the toilet).
- Flush the toilet to drain the tank. Soak up remaining water with a sponge or towel.
- Disconnect the supply line from the bottom of the tank.
- Unscrew the locknut securing the fill valve inside the tank.
- Remove and replace the old valve with a compatible Kohler part.
- Reattach the locknut and water supply line.
- Turn on the water and test for leaks.
This ensures the water control mechanism is working smoothly.
Method 3: Adjust or Replace the Flush Chain
The chain connecting the trip lever and flapper is crucial. If it’s the wrong length or broken, the flapper won’t seal properly.
How to fix:
- If the chain is too short, the flapper stays slightly open.
- If it’s too long, it may get caught under the flapper.
- Adjust the chain to have about ½ inch of slack.
- Replace it if it’s corroded, tangled, or broken.
Test the flush after adjustment to ensure the flapper seals tightly.
Method 4: Inspect and Replace the Flapper
A worn-out flapper is one of the most common causes of a running toilet. Kohler flappers are typically made of rubber and can degrade over time.
Signs your flapper needs replacement:
- Toilet runs after every flush
- Flapper doesn’t close completely
- Water leaks into the bowl without flushing
Fix:
- Turn off the water supply and drain the tank.
- Detach the old flapper from the flush valve.
- Clean the flush valve seat using a sponge with vinegar and water.
- Attach a new compatible flapper.
- Connect the chain and test the flush.
Ensure the flapper forms a complete seal to stop leaks.
Method 5: Replace the Flush Valve and Gasket
If the flapper replacement doesn’t stop the running, the flush valve or tank-to-bowl gasket might be compromised.
Steps:
- Turn off water and drain the tank.
- Unscrew the tank-to-bowl bolts using a wrench.
- Lift the tank and lay it gently on a towel.
- Remove the old flush valve by loosening the large nut underneath.
- Replace with a new flush valve that matches your Kohler model.
- Replace the tank-to-bowl gasket to ensure a tight seal.
- Reattach the tank, tighten bolts evenly, and reconnect the water supply.
Test for leaks. This is a more involved repair but solves deep-seated leakage problems.
Method 6: Adjust the Float Rod or Float Cup
If your toilet’s tank fills beyond the overflow tube, the float mechanism may be the problem.
Instructions:
- For older models with float rods and balls, gently bend the rod downward to lower the fill level.
- For modern float cup systems, locate the adjustment screw and rotate counterclockwise to lower the water level.
- Flush and observe where the water stops.
The float is what tells the fill valve to stop the water. Keeping it properly adjusted is essential for efficient operation.
Method 7: Inspect the Overflow Tube and System Alignment
The overflow tube prevents the tank from flooding but can signal a leak if constantly draining water.
Check:
- Is the tube cracked or broken?
- Is water constantly running into it?
- Is the tube height correct?
Ensure the float and flapper mechanism is not allowing excessive water to rise and spill. If the overflow tube is damaged, it may need full replacement along with the flush valve.
When to Call a Plumber
If you’ve tried all the methods above and your toilet is still running, it could indicate:
- Cracks in the tank or base
- Faulty internal components that need professional replacement
- Complex internal leaks or sediment buildup in supply lines
Hiring a plumber might cost more upfront but could save long-term damage and high water bills.
Tools You May Need for Repairs
To repair a running Kohler toilet, keep the following tools on hand:
- Adjustable wrench
- Screwdriver
- Sponge or towel
- Locking pliers
- Vinegar and soft cloth
- Replacement parts (flapper, fill valve, flush valve, chain)
All these tools are inexpensive and widely available at local hardware stores or online.
Water-Saving Tip
If you’re replacing old parts, consider installing Kohler’s eco-friendly components such as low-flow fill valves or dual-flush systems. These can help conserve water and reduce your utility bill even further.
Preventive Maintenance Tips
To avoid future issues:
- Inspect the inside of your toilet tank every 3–6 months.
- Replace rubber parts (like flappers) every 1–2 years.
- Check for mineral deposits or corrosion.
- Don’t use harsh chemicals that can degrade seals and valves.
Routine maintenance goes a long way in preventing a running toilet.
Final Thoughts
Dealing with a running Kohler toilet can feel like a hassle—but it doesn’t have to be. With some basic tools and the right guidance, you can fix the issue in under an hour. From replacing a worn flapper to adjusting the float, each step contributes to better water efficiency and peace of mind.
Remember, the faster you act, the more water and money you’ll save. Whether you’re handling it yourself or calling in a professional, stopping your Kohler toilet from running is an investment in your home’s functionality and sustainability.
We are really lucky to have a hard-working, multi-skilled plumber on our team. Collin D. Gallegos, a professional plumber who has worked with us since 2012, is an expert in vent, septic, and drainage systems. He is a Certified Master Plumber and has worked on various commercial plumbing projects. He usually helps our readers resolve plumbing and pipe-related issues with a proper DIY troubleshooting and repair guide.