A running toilet is not only an annoying issue but also one that can waste gallons of water every day—leading to higher utility bills and potential damage to your home’s plumbing system. If you own a Toto toilet and find yourself wondering, “Why does my Toto toilet keep running?” — you’re not alone. Even though Toto produces some of the most reliable and innovative toilets on the market, they can still develop running problems due to wear and tear or minor mechanical failures.
In this 2025 updated guide, we will walk you through the most common reasons your Toto toilet might keep running, how to diagnose each issue, and practical solutions to fix the problem quickly. By the end, you’ll know exactly what to look for and how to stop your Toto toilet from running once and for all.
Why Does My Toto Toilet Keep Running?
When your Toto toilet is working correctly, the tank refills after each flush and stops when the correct water level is reached. If some internal components become damaged or misaligned, water can continue running into the bowl—causing a constant running toilet.
The most common reasons include:
✅ A worn-out or cracked flapper
✅ A broken or tangled chain
✅ Debris in the tank affecting seals
✅ A misaligned or damaged float valve
✅ An incorrectly positioned refill tube
Below, we’ll take a closer look at each of these common causes:
1. Cracked or Worn Flapper
The flapper is a soft rubber seal that lifts during flushing and closes when the tank refills. Over time, flappers can crack, warp, or lose flexibility—preventing a tight seal on the flush valve opening.
How it causes running:
If the flapper is unable to form a proper seal, water will continuously leak into the bowl, causing the fill valve to keep refilling the tank endlessly.
Solution:
Carefully inspect the flapper for cracks, warping, or stiffness. If you notice wear, replace it with a new Toto-approved flapper.
2. Broken or Misadjusted Chain
The chain connects the toilet handle (trip lever) to the flapper. If this chain is broken, tangled, too short, or too long, the flapper may not open or close properly.
How it causes running:
- A chain that’s too short may prevent the flapper from fully closing.
- A chain that’s too long may tangle, causing the flapper to stay open.
Solution:
Adjust the chain length so that it has just enough slack for full movement—without catching or preventing a proper seal.
3. Debris in the Tank
Mineral deposits, sediment, or debris can accumulate in the tank—especially if you live in an area with hard water. This buildup can prevent the flapper from sealing tightly or interfere with other tank components.
How it causes running:
Debris prevents the flapper from sitting flush against the valve seat, allowing water to leak continuously.
Solution:
Clean the inside of the tank regularly with a gentle brush and non-abrasive cleaner. Remove all debris from the flapper seat.
4. Damaged or Misaligned Float Valve
The float valve controls how much water fills the tank after each flush. If the float is damaged or incorrectly set, the water level may rise too high—causing constant running.
How it causes running:
When the float fails to shut off the fill valve, excess water flows down the overflow tube into the bowl.
Solution:
Adjust the float to set the water level about 1 inch below the top of the overflow tube. If the valve is damaged, replace it with a new Toto float valve.
5. Incorrectly Positioned Refill Tube
The refill tube is a small flexible tube that refills the bowl after each flush. If this tube is inserted too far into the overflow tube or is too long, it can siphon water—creating constant running.
How it causes running:
Incorrect positioning can create a siphon effect, drawing water continuously into the bowl.
Solution:
Clip the refill tube to the overflow tube—not inside it—and trim the tube to the correct length.
Preventive Maintenance Tips
To help prevent your Toto toilet from running:
- Inspect the tank components twice a year
- Replace the flapper every 3–5 years
- Use genuine Toto parts for repairs
- Clean the tank regularly
- Adjust the float valve as needed
FAQs: Why Does My Toto Toilet Keep Running?
Q1: Why does my new Toto toilet keep running?
Even new toilets can run if the flapper chain is improperly adjusted or if the float valve is set too high. Always check these components after installation.
Q2: How do I fix a running Toto toilet?
Identify the cause (flapper, chain, debris, float, refill tube), then repair or replace the faulty part. In most cases, you can resolve the issue in less than 30 minutes.
Q3: Can hard water cause my Toto toilet to run?
Yes. Mineral deposits from hard water can cause the flapper to fail or interfere with seals, leading to a running toilet.
Q4: Is a running toilet dangerous?
While not dangerous, it wastes a significant amount of water—leading to higher water bills and potential environmental impact.
Q5: When should I call a plumber for a running Toto toilet?
If basic cleaning and adjustments do not fix the issue—or if you suspect a more serious valve or plumbing problem—consult a professional plumber.
Final Thoughts
If you’ve been asking yourself, “Why does my Toto toilet keep running?”, now you have the answers! While Toto toilets are among the most reliable on the market, small issues can still cause them to run continuously. With this updated guide, you can easily diagnose the problem, perform the necessary repairs, and restore your toilet to optimal performance—saving water and lowering your utility bills.
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.