Here’s Why & How to Fix It
That persistent sound of water trickling into your toilet bowl isn’t just annoying—it’s expensive. A constantly running toilet can waste between 30 to 200 gallons of water per day, adding significant costs to your water bill. Over a year, this single fixture could waste over 6,000 gallons of water, costing you hundreds of dollars unnecessarily.
The good news? Most running toilet problems have simple causes and solutions. Understanding what’s happening inside your toilet tank empowers you to either fix the issue yourself or communicate effectively with a plumber about what needs repair.
Understanding How Your Toilet Works
Before diagnosing problems, it helps to understand the basic components inside your toilet tank. When you flush, the flush lever lifts the flapper or tank ball, allowing water to rush from the tank into the bowl. As the tank empties, the float drops, opening the fill valve to refill the tank. Once the float reaches the proper height, the fill valve closes, stopping water flow.
When this system works correctly, your toilet fills after flushing and then stays silent. When something malfunctions, water continues running, either into the bowl through the flapper or into the overflow tube.
Common Causes and Solutions
1. Faulty Flapper Valve
The flapper is the rubber seal at the bottom of your tank that lifts when you flush and then reseats to hold water in the tank. Over time, mineral deposits, algae, and general wear cause flappers to deteriorate, warp, or become misaligned. When the flapper doesn’t seal properly, water continuously leaks from the tank into the bowl.
How to identify it: Add a few drops of food coloring to your tank water. Wait 15 minutes without flushing. If color appears in the bowl, your flapper is leaking.
The fix: Flappers are inexpensive and easy to replace. Turn off the water supply to your toilet using the shutoff valve behind the toilet. Flush to empty the tank. Remove the old flapper from the overflow tube and disconnect it from the chain. Install the new flapper, ensuring it’s properly aligned and the chain has minimal slack—about half an inch. Turn the water back on and test.
2. Improperly Adjusted Float
The float tells the fill valve when to stop filling the tank. If set too high, water continuously flows into the overflow tube. If too low, your toilet won’t flush effectively.
How to identify it: Water flows into the overflow tube (the vertical tube in the center of your tank), or your tank doesn’t fill to the water line marked inside.
The fix: For ball floats attached to a rod, bend the rod downward slightly to lower the water level. For cylinder floats that slide on the fill valve, squeeze the adjustment clip and move the float down about an inch. Flush and observe the fill level. Adjust until water stops about an inch below the top of the overflow tube.
3. Defective Fill Valve
The fill valve (also called a ballcock) controls water flow into the tank. When it malfunctions, it may not shut off completely, causing continuous water flow and that characteristic hissing sound.
How to identify it: Continuous hissing sound, water flowing into the overflow tube, or the toilet running even after adjusting the float.
The fix: While you can sometimes clean mineral deposits from fill valves, replacement is often more reliable. Turn off the water supply and flush to empty the tank. Disconnect the water supply line from the bottom of the tank. Remove the locknut holding the old fill valve and lift it out. Install the new fill valve according to manufacturer instructions, reconnect the water supply, and adjust the float to the proper level.
4. Overflow Tube Issues
The overflow tube prevents tank overflow by directing excess water into the bowl. If this tube cracks or breaks, or if the water level is set too high, water constantly flows into it.
How to identify it: Water visibly flowing into the overflow tube, or a cracked/damaged tube.
The fix: Lower the float to reduce water level below the overflow tube opening. If the tube itself is damaged, it typically requires replacing the entire flush valve assembly—a more involved repair that many homeowners prefer to leave to professionals.
5. Flush Lever and Chain Problems
The chain connecting your flush lever to the flapper must have the right amount of slack. Too much slack and your toilet won’t flush completely. Too little slack and the flapper can’t seat properly, causing constant running.
How to identify it: Flapper appears tilted or doesn’t close fully, or you must hold the handle down for a complete flush.
The fix: Adjust the chain length to leave about half an inch of slack when the flapper is seated. Remove excess links if the chain is too long. Ensure the chain isn’t tangled or caught under the flapper. If the flush lever itself is corroded or broken, replace it—they’re inexpensive and available at any hardware store.
6. Refill Tube Positioning
The small flexible refill tube connects from the fill valve to the overflow tube, sending water into the bowl to refill the trap after flushing. If this tube falls out of the overflow tube or is positioned incorrectly, you might hear constant running water.
How to identify it: The refill tube isn’t clipped to or inserted into the overflow tube, or water sprays around inside the tank.
The fix: Simply reposition the refill tube so it clips onto or directs water into the overflow tube. This tube should never extend down into the overflow tube—it should direct water into it from above.
Preventive Maintenance
Regular maintenance prevents many running toilet problems:
Clean your tank regularly. Mineral deposits and sediment accumulate over time, affecting component function. Every few months, turn off the water supply, flush to empty the tank, and wipe down all components with a vinegar solution to remove mineral buildup.
Replace flappers every 3-5 years. Even if not currently leaking, old flappers become brittle and fail eventually. Proactive replacement during routine maintenance prevents future problems.
Check for leaks periodically. Use the food coloring test quarterly to catch small leaks before they become expensive.
Address hard water issues. If you have hard water, consider a water softener to reduce mineral buildup that damages toilet components and other plumbing fixtures.
When to Call a Professional
While many running toilet fixes are DIY-friendly, certain situations warrant professional help:
- You’ve tried basic fixes but the toilet still runs
- The problem involves the toilet base or floor flange
- You notice water pooling around the toilet base
- Multiple toilets in your home are running
- Your toilet is old and experiencing multiple simultaneous problems
- You’re uncomfortable working with plumbing components
Professional plumbers diagnose problems quickly and have the tools and parts to fix issues on the spot. What might take you hours of trial and error takes an experienced plumber minutes to resolve.
The Cost of Ignoring the Problem
Beyond the direct water waste, constantly running toilets create additional problems:
Higher water bills are the most obvious consequence. Even a moderate leak can add $50-100 or more to your monthly bill.
Component wear accelerates when parts constantly operate. A running toilet stresses the entire system, shortening the lifespan of multiple components.
Water damage risk increases if the problem stems from a failing fill valve that allows overfilling. While overflow tubes prevent immediate flooding, chronic overfilling can lead to tank cracks or other failures.
Environmental impact matters too. In drought-prone areas, wasting hundreds of gallons daily is irresponsible when water conservation is critical.
The Bottom Line
A running toilet is rarely an emergency, but it’s never a problem to ignore. Most causes have simple, inexpensive fixes that take under an hour to complete. Even if you’re not particularly handy, replacing a flapper or adjusting a float is manageable with basic tools and patience.
Start by identifying which component is causing the problem. Try the appropriate fix based on what you discover. If DIY repairs don’t resolve the issue, don’t let frustration lead to overtightening parts or forcing components—call a professional plumber to diagnose and repair the problem correctly.
Your toilet is one of the most-used fixtures in your home. Keeping it functioning properly protects your water bill, conserves a precious resource, and ensures this essential fixture is always ready when you need it. Don’t let a running toilet run away with your money—take action today to stop the waste and restore normal function. Mr. Rooter Plumbing, Orange County, 949.371.2025