Edited: September 22, 2025
Few things are more annoying than a toilet that won’t stop running. Beyond the sound, it can waste hundreds of gallons of water each day, driving up your bill and putting unnecessary stress on your plumbing. Luckily, most causes of a constantly running toilet are simple to identify — and often easy to fix. Let’s walk through the most common reasons, DIY solutions, and when to call in the experts at Radiant Plumbing & Air Conditioning here in Austin and San Antonio.
Homeowner, Meet Your Toilet
Inside your toilet tank, a few key parts control the flush and refill cycle:
- Flapper valve – seals the tank and lifts during a flush
- Fill valve – refills the tank after each flush
- Float – signals when to stop filling
- Overflow tube – prevents flooding by redirecting excess water
- Handle and chain – lift the flapper when you flush
When one of these parts wears out, misaligns, or fails, the toilet may keep running.
5 Common Causes of a Toilet That Keeps Running
So why does this porcelain troublemaker keep gurgling away? There’s no single villain, but a handful of usual suspects show up time and again. Let’s start with the one we see most often: the flapper.
Worn or Warped Flapper
The flapper is a rubber piece at the bottom of the tank. Over time, it can warp, crack, or fail to seal, allowing water to leak into the bowl.
Fix: Do a simple dye test by adding food coloring to the tank. If the color seeps into the bowl without flushing, replace the flapper (a $5–$10 fix).
Flapper Chain Issues
If the chain is too tight, the flapper won’t close fully. If it’s too loose, it can tangle and prevent a proper seal.
Fix: Adjust the chain so there’s about ½ inch of slack.
Float or Fill Valve Problems
If the float is set too high, water overflows into the overflow tube, keeping the toilet running. If the fill valve is worn or sticking, it may never shut off.
Fix:
- Adjust the float so water sits about 1 inch below the overflow tube.
- If that doesn’t help, replace the fill valve assembly ($20–$40 and about 30 minutes of work).
Overflow Tube Issues
A cracked or misaligned overflow tube can let water continuously trickle out.
Fix: Inspect for cracks and replace if necessary.
Handle Sticking
Sometimes, the problem is as simple as a handle that won’t return to its resting position.
Fix: Tighten the handle nut inside the tank or replace the handle if worn.
Step-by-Step: Diagnosing a Running Toilet
- Remove the tank lid carefully. Set it on a flat, safe surface so it doesn’t crack. This gives you a clear view of the inner workings.
- Flush the toilet once. Watch how the parts move together. Pay attention to the flapper, the chain, the float, and the fill valve.
- Check the flapper as the water drains. The flapper should lift smoothly, then settle back into place to seal the opening. If it sticks, warps, or doesn’t fully close, water will continue to leak into the bowl.
- Listen for ongoing trickling. Place your ear near the tank. If you hear constant running or dripping, it may be flowing into the overflow tube — a sign of a float or fill valve problem.
- Measure the water level. After the tank refills, the water should stop about an inch below the top of the overflow tube. If it rises higher, the float is likely set too high or the fill valve is malfunctioning.
- Inspect the chain and handle. Make sure the chain has a little slack but isn’t tangled. A chain that’s too tight or too loose can stop the flapper from sealing.
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Adjust or replace as needed.
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- Adjust the float by lowering it until the water stops at the correct level.
- Shorten or lengthen the flapper chain for proper movement.
- If the flapper or fill valve looks worn or cracked, replacement is usually a simple, inexpensive fix.
By following these steps, you’ll narrow down the cause of your running toilet and know whether a quick adjustment will solve the problem or if a replacement part is needed.
When to Call the Professionals
Some running toilets can be tamed with a quick DIY fix, but others are stubborn enough to need a pro. That’s where Radiant comes in. If you’re facing any of these situations, it’s time to skip the guesswork and call our team:
- The shut-off valve is damaged or won’t close all the way
- You’ve already replaced the flapper or fill valve but the toilet still runs
- Cracks are visible in the tank or overflow tube
- More than one toilet in your home is affected — a sign of a bigger water pressure problem
Our licensed Austin & San Antonio plumbers are ready 24/7 to solve the issue fast. And if it’s after hours, you don’t have to wait — our emergency plumbers are always available to stop the running, prevent water waste, and keep your bathroom in working order.
Preventing Future Problems
The best way to stop a running toilet from turning into a repeat offender is regular maintenance. A quick look inside the tank every six months can catch worn parts before they waste gallons of water. Flappers, in particular, wear out quickly in Austin’s hard water and often need replacement every few years. Cleaning away mineral buildup and upgrading old fill valves to modern, efficient ones also extends the life of your toilet.
Of course, most homeowners don’t want “toilet checkups” on their to-do list. That’s why we created the Radiant Care Club. As a member, you’ll get scheduled plumbing tune-ups, priority service, and expert eyes on every part of your home’s plumbing system — including those pesky toilet parts that love to fail at the worst possible time. Think of it as insurance against surprise plumbing headaches, with the added bonus of saving money on repairs down the road.
Stop Wasting Water – Just Call Radiant.
If your toilet won’t stop running and DIY fixes don’t do the trick, Radiant Plumbing & Air Conditioning is here for you. We’ve been helping Austin homeowners install and fix their toilets since 1999 with fast, reliable plumbing repairs — available 24/7. Schedule online today and get your bathroom back to normal.
