How to Fix a Running Toilet

That constant trickling sound from your toilet isn’t just irritating—it’s quietly running up your water bill. A running toilet can waste hundreds of gallons of water each day, adding unnecessary cost and putting stress on your plumbing system. Most of the time, the fix is simple and can be done with just a few tools and a little know-how. Ignoring it, however, can lead to bigger problems down the line. 

Whether you’re comfortable making repairs yourself or just want to understand what’s going on, we’re here to help. In this blog, Donnelly’s Plumbing, Heating & Cooling walks you through the common causes of a running toilet—and what you can do about it.

Why Your Toilet Won’t Stop Running

When your toilet keeps running long after you’ve flushed, it usually means something inside the tank isn’t working quite right. This isn’t just a minor annoyance—it’s a sign that water is continuously flowing from the tank into the bowl or down the overflow tube. Over time, that can lead to hundreds—or even thousands—of gallons of wasted water each month.

Here are the most common reasons:

• Worn or misaligned parts inside the tank
  
• Improper water level settings causing constant refilling
  
• Mineral buildup or debris interfering with valve function
  

The good news? Most of these issues can be spotted with a quick visual check inside the tank and fixed with inexpensive parts or simple adjustments.

Common Causes of a Running Toilet

Once you open the tank, most running toilet issues are easy to spot. Here are the most frequent culprits—and how they cause that never-ending water flow.

Flapper Isn’t Sealing Properly

The flapper is a rubber piece at the bottom of the tank that lifts when you flush and seals shut to hold water in the tank afterward.

• Over time, it can become warped, cracked, or coated in buildup, preventing a full seal.
  
• When the seal fails, water leaks slowly into the bowl, triggering the fill valve to keep refilling the tank.

Float is Set Too High or Malfunctioning

The float controls how much water fills the tank. If it’s too high, the tank overfills and drains into the overflow tube.

• You might hear water running long after flushing.
  
• A simple float adjustment often solves the problem—but older floats may need to be replaced entirely.

Chain is Too Tight or Tangled

The chain that connects the flush handle to the flapper can cause issues if it’s not the right length.

• A chain that’s too short or kinked can hold the flapper open slightly, causing continuous leakage.
  
• Adjusting the chain length is a quick, easy fix.

Fill Valve or Flush Valve Needs Replacing

Sometimes the problem is with the valves themselves:

• Worn fill valves may not shut off properly
  
• Leaky flush valves can mimic a flapper problem
  
• If the internal components are old or corroded, replacement is often more effective than repair

How to Fix a Running Toilet (Step-by-Step)

Many running toilet problems can be fixed with a few basic tools and some patience. Here’s how to troubleshoot and repair the issue safely.

1. Turn Off the Water Supply

• Locate the shut-off valve behind the toilet near the floor.
  
• Turn it clockwise to stop water flow to the tank.

2. Remove the Tank Lid

• Carefully lift off the lid and place it somewhere safe.
  
• Flush the toilet to empty the tank and observe how the components work.

3. Inspect the Flapper

• Check for warping, cracks, or buildup.
  
• If it doesn’t seal properly, replace it with a matching model (easy to find at hardware stores).

4. Check and Adjust the Chain

• Make sure the chain has a slight slack when the flapper is closed.
  
• Remove kinks or excess tension to ensure the flapper can close fully.

5. Adjust the Float

• If your toilet uses a float arm, gently bend it downward to lower the water level.
  
• For a float cup, look for an adjustment screw or clip on the fill valve.

6. Replace Valves if Needed

• If the fill valve or flush valve appears damaged or doesn’t respond to adjustments, it’s best to replace it entirely.
  
• Most kits come with simple instructions and take under 30 minutes to install.

7. Turn Water Back On and Test

• Slowly reopen the shut-off valve.
  
• Let the tank fill, then flush several times to ensure everything’s working smoothly.

When to Call a Plumber

While many running toilet issues are easy to fix, there are times when a professional plumber is the best solution. If DIY attempts haven’t stopped the water—or if new issues arise—it’s time to bring in the experts from Donnelly’s Plumbing, Heating & Cooling.

Call a plumber if:

• The toilet continues to run after you’ve replaced or adjusted parts
  
• There’s water leaking onto the floor or around the toilet base
  
• Internal tank parts are corroded, broken, or incompatible with modern components
  
• You’re dealing with an older toilet and want to upgrade to a more efficient model
  
• You’d prefer peace of mind with a professional diagnosis and long-term fix
  

Professional plumbing ensures the job is done right the first time—and prevents small annoyances from becoming bigger (and costlier) problems down the line.

Stop the Trickling With Help From Donnelly’s

A running toilet may seem like a minor nuisance, but over time it can lead to serious water waste and higher utility bills. Fortunately, most of the common causes—like a worn flapper or misaligned float—can be fixed quickly with a few adjustments or part replacements. But when the issue goes beyond a simple DIY fix, professional help can make all the difference.

At Donnelly’s Plumbing, Heating & Cooling, we’ve been helping Lansdale homeowners stop the drip and restore peace of mind for decades. Whether you need a fast repair or want to upgrade to a water-saving toilet, we’re just a call away.

Contact us today for expert plumbing service that gets it done right—the first time.