Toilet Keeps Running? 5 Causes and Easy Fixes (Before You Call a Plumber) 

That dreaded sound. You know exactly what it is. It is the steady, quiet trickling of water or the sudden, phantom flush *WHOOSH* of a running toilet in the middle of the night. You won’t be cheering on your toilet if it’s making these noises. But it’s a pretty good indication something needs to be done, soon.

A running toilet is a massive waste of resources. A single running toilet can waste anywhere from 30 to 200 gallons of water every single day. When your next water bill arrives, that phantom noise turns into a very real expense.

Running Toilet Cost Breakdown

Your first instinct might be to call a professional plumbing company like Baethke. But let’s be completely honest, as plumbing professionals for over 30 years, we know that a simple running toilet can probably be fixed by you with minimal expense. By the time you pay a standard diagnostic fee and labor for professional plumbing services, a quick 10-minute repair can easily cost you $150 to $300.

This troubleshooting roadmap will help you understand the components of your toilet and how to repair them. We will go over the most common reasons a toilet keeps running, and how you can fix them yourself. 

What to Look for in Your Toilet Tank When it’s Running

To fix the problem, you first need to understand what is happening inside the tank. Go ahead and take the heavy porcelain lid off your toilet tank and set it carefully on the floor.

Inside, you will see a few key components:

• The Flush Valve / Flapper: This is the rubber plug at the bottom of the tank. When you push the handle, a chain lifts this flapper, allowing water to rush into the bowl.
• The Fill Valve: This is the tall tower assembly (usually on the left side). Its job is to refill the tank with water after a flush.
• The Float: Either a round ball on a metal rod or a cylindrical cylinder that slides up and down the fill valve. It rides the water level; when it reaches a certain height, it tells the fill valve to shut the water off.
• The Overflow Tube: A hollow tube in the center of the tank. If the water level gets too high, it drains into this tube to keep your bathroom from flooding.

The 5 Most Common Reasons Your Toilet is Running  

1. Check for a Faulty or Deteriorated Tank Seal (Flapper)

The rubber flapper at the bottom of your tank lives its entire life submerged in water. Over time, chemicals like chlorine in your city water supply cause the rubber to warp, rot, or become covered in slimy mineral scale. Generally speaking, these need to be replaced every 3 to 5 years.

• The Problem: If the rubber flapper loses its flexibility or develops cracks, it can no longer form a clean, watertight seal against the plastic drain seat below it. Water will silently trickle into the bowl 24/7.
• The Fix: Simply put 2 or 3 drops of food coloring in your tank. If you wait a few minutes and see the dye in your bowl, you know you have a bad flapper. You can snap a new one into place for less than $10 without any tools.

 2. Overflow Tube Water Level (Adjust the Float)

If you look into your open tank and notice that water is constantly spilling over the top edge of the open overflow tube, your fill valve is simply supplying too much water.

• The Problem: The float is set too high. Because the water level never reaches the float’s “cut-off point,” the fill valve keeps running forever, and the excess water simply dumps safely down the overflow tube.
• The Fix: If you have an older toilet with a long brass rod and a floating ball, gently bend the rod downward slightly to lower the ball. If you have a modern fill valve with a plastic cylinder float, locate the long plastic adjustment screw next to it. Use a screwdriver or your fingers to turn the screw counterclockwise. This lowers the float height. Aim to have the water level sit about one inch below the top of the overflow tube.

3. Adjust the Chain Link

Look at the silver or plastic chain connecting your toilet handle lever to the rubber flapper at the bottom of the tank. This chain needs a tiny bit of slack, but not too much.

• The Problem: If the chain is too short, it will pull up on the flapper constantly, preventing it from sealing completely. Water will constantly leak underneath it. If the chain is too long, it can get caught underneath the flapper when it closes, propping it open.
• The Fix: Unhook the small clip on the chain. Adjust it so there is about one-quarter to one-half inch of slack in the chain when the handle is at rest. Drop it back into place and test a flush.

4. Clear Debris from the Fill Valve

Sometimes, the mechanical components of the toilet are perfectly fine, but a tiny piece of mineral scale or rust from your home’s water lines gets stuck inside the internal mechanism of the fill valve.

• The Problem: Debris physically blocks the internal seal from shutting completely, causing a small, continuous hiss of water to enter the tank even when the float is fully raised.
• The Fix: Turn off the water valve at the wall. Carefully twist off the top cap of your fill valve (place your hand over it, press down, and twist counterclockwise). Hold a cup over the open valve and turn the main water valve back on slowly for just a few seconds. The water pressure will flush out any trapped grit or sediment. Put the cap back on and test the system.

5. Replace the Entire Fill Valve

If you have tried adjusting the float and cleaning the valve, but the water still refuses to stop running, the internal seals of your fill valve have likely failed due to age.

• The Problem: Fill valves typically last 5 to 7 years. When they break down internally, adjustments won’t help.
• The Fix: Don’t panic. Replacing a fill valve is a straightforward DIY task. Buy a fill valve kit for your specific brand of toilet. Most of them will cost about $15 to $20. Turn off the water, drain the tank, sponge out the remaining water at the bottom, unscrew the supply line beneath the tank, remove the old valve, and drop the new one in. Follow the box instructions to tighten the locknut and reattach your water line. 

Note: When replacing the tank seal, or fill valve kit, make sure that you replace them with the exact same one for your toilet’s specific brand. Using parts that are not brand specific will lead to additional more expensive problems.

When Is It Time to Call a Plumber to Fix Your Running Toilet

We pride ourselves on being honest. While we want you to save money by handling these easy steps, there are instances where DIY fixes can cause more harm than good.

Always double-check your work and make sure you have completed these repairs correctly. If you ever have any questions or doubts about your repair job, you can always have one of our insured plumbing contractors come out and check your work. This service call ($129.50) could potentially save you thousands of dollars in water damage.  

You should stop and call a licensed plumber if:

• The shut-off valve at the wall is frozen or leaking: If you try to turn off the water behind your toilet and the valve won’t budge, or if it starts leaking onto your floor, stop immediately. Forcing a corroded valve can snap the pipe inside the wall, leading to a catastrophic household flood.
• You notice cracks in the porcelain: If you see hairline fractures in the tank or bowl while working on the toilet, the structural integrity of the fixture is compromised. It needs to be replaced before it cracks completely and floods your home.
• The running is accompanied by sewer smells or clogs: If your toilet runs and you also experience frequent backups or gurgling in your shower drains, the issue isn’t inside your tank—it is a blockage deep within your main sewer line.

Your running toilet wastes significant water and money, but don’t worry, you can fix most minor issues quickly by following these basic DIY troubleshooting tips. By taking 15 minutes to diagnose the issue yourself, you protect your wallet from unnecessary service fees and gain a better understanding of how your home works.

You can easily solve common toilet tank problems like faulty flappers or misadjusted floats, saving on money on professional service calls.

And remember, you can always contact Baethke for professional plumbing services if the repair exceeds your standard DIY knowledge and capabilities. 

Frequently Asked Questions

• Why won’t my toilet stop running?
  In most cases, it’s a worn or misaligned flapper, the rubber valve at the bottom of the tank, that isn’t sealing fully. This lets water slowly leak into the bowl, causing the fill valve to keep topping off the tank. 
• Can I fix it myself?
  Sometimes. Replacing a $5 to $10 flapper solves the problem in many cases. If that doesn’t work, the problem may be the fill valve, a cracked overflow tube, or an issue with the flush valve seal. If any of these problems feel too complicated for you to fix, please call a professional plumber.
• Is a running toilet actually costing me money?
  Yes, a running toilet can waste up to 200+ gallons of water a day, showing up as a real spike on your water bill. It’s worth fixing as soon as you can.