How to Stop a Toilet from Running (and Why It Matters for Your Water Bill)

There are two different types of running toilets. The first type is the one that you can hear, and that is usually a steady hiss or a slow trickle that you will always become aware of when the rest of the house is quiet. The second type is the type that you don’t even hear, a slow leak that only becomes apparent when you get your water bill and see a number that is just too large for no apparent reason.

Either way, you are wasting the same thing: money. A toilet that has a slow leak in the flapper that you don’t even hear can waste over 200 gallons a day. A fast-running toilet will waste 4,000 gallons a day.

The fix is almost always one of these three things: the flapper is worn out, the float is installed too high, or the fill valve is malfunctioning. All of these are easy repairs that any beginner can do. All of these repairs are under $15 to fix. None of these repairs require the assistance of a plumber. The hardest part of this job is figuring out which of these problems you are dealing with, and this article will walk you through that process.
Note: This article is meant to be read in conjunction with our original article on fixing a running toilet, which goes through the entire step-by-step process of fixing these different parts of the toilet.

The Real Cost of a Running Toilet

While most people understand that running toilets are inefficient, the actual figures are shocking enough to warrant the repair as a necessity rather than a luxury.
⦁ Slow silent flapper leak: 30 to 200 gallons daily.
⦁ Moderate running toilet: 200 to 1,000 gallons daily.
⦁ Fast running toilet (audible hiss): up to 4,000 gallons daily.
⦁ Actual Cost: $0.005 per gallon average cost for water in the United States; $55 to $365 per year for one toilet for the silent flapper leak.
⦁ Actual Cost: $365 to $1,825 per year for one toilet for the moderate running toilet.
⦁ Actual Cost: Over $7,000 per year for one toilet for the fast running toilet.
⦁ Repair Cost: $4 to $15 for parts; 20 minutes of your time.

🔑 Key Insight: The Environmental Protection Agency estimates that household toilet leaks account for almost 1 trillion gallons of wasted water across the nation annually. A great deal of this is because of toilets where the homeowner simply does not know their toilet is running, because of a slow leak. The food coloring test below reveals leaks that are completely inaudible.

How to Tell if Your Toilet is Running Silently

If you can hear it running, it’s clear what’s going on. But many toilets don’t make a sound. The flapper is leaking slowly enough so you can’t hear the water running into the bowl, but fast enough so it wastes hundreds of gallons per day.
The food coloring test will reveal silent running in just 15 minutes, and it’s absolutely free.

1. Add 10 drops of food coloring to the toilet tank. It doesn’t matter what color it is.
2. Wait 15 minutes. Don’t flush during this time.
3. Look in the toilet bowl. If you can see any color in the bowl, it means there’s a leak from the tank into the bowl, through the flapper. Even if it’s just a little color, it means there’s a leak. If you don’t see any color, it means everything is working correctly.
   💡 Pro Tip: Don’t just do this on the toilet you suspect of running. Do it on all of them. Silent flapper leaks can occur on perfectly functioning toilets. Many people discover they’ve been paying for a leak they didn’t even know was happening for months or years.

Understanding the 3 Common Causes

The Flapper — Most Common Cause

Flapper: This is the rubber that covers the flush valve hole on the bottom of the tank. When you flush the toilet, the flapper will come up to allow water to flow into the bowl. When the tank is refilled, the flapper goes back down, sealing the flush valve hole. A bad flapper will leak water from the tank into the bowl constantly.

Flappers usually have a lifespan of 3 to 5 years, until the rubber becomes stiff and warps. Chlorine in the water and tablets that are dropped in the tank will accelerate the deterioration of the flapper. This is by far the most common cause of a running toilet, accounting for 80% of all running toilets.

The Float — Quick Free Fix

The float works as a signal to the fill valve to stop refilling the tank. If the float is adjusted too high, the water level will be higher than the overflow tube, which is the tall tube in the middle of the tank. The water will drain into the bowl through this tube. You can see this happening if you look at the tank and take off the lid. The water draining into the tube is a dead giveaway.
Making this adjustment costs nothing and only takes 30 seconds.

The Fill Valve — Least Common

The fill valve is the tall device that refills the tank after each flush and closes when water reaches the appropriate level. A bad fill valve doesn’t close properly, continuing to add water to the tank, which overflows and goes down the overflow tube. This is not as common as a bad flapper, but more common than you might think, especially with old toilets.

The 3-Step Diagnosis Process

Run through these three tests in order. Stop when you find the cause.

Test 1: Food Coloring Test (Flapper Leaks)

Already explained above.
Color appears in the bowl without flushing = Worn Flapper.
This test alone accounts for 80% of running toilet problems.

Test 2: Overflow Tube Visual (Float Issues)

Take off the tank lid and observe the water level as the tank fills up.
Water level should stop about 1 inch before the top of the overflow tube.
If the level goes up beyond this point and you see water trickling into the overflow tube, your float is too high and you need to adjust it down.

Test 3: Float Lift Test (for fill valve failure)

As you are filling your tank, you should stick your hand into the toilet and manually hold up the float as if the water level is higher than normal. If the running water is stopped when you manually hold up the float, you should simply adjust the float (free fix). However, if the running water is not stopped even when you manually hold up the float all the way, you should replace your fill valve ($10-$15).

🔑 Key Insight
If you aced the food coloring test, and your results from the visual inspection of the overflow tube showed that the water level is below the rim of the tube, and if you also stopped the running water from the float lift test, then you should know that your toilet is NOT running! You might actually hear running water in your pipes, which is causing a water hammering effect. It might also be coming from your supply line, so you should also look for drips coming from the supply valve behind your toilet.

Fix 1: Replace the Flapper

The most common toilet repair, the replacement of the flapper, is also the easiest of all the repairs you might have to do on your home.
No tools required.
5 minutes.

1. Turn off the water supply behind the toilet by turning the oval-shaped valve on the wall clockwise.
2. Empty the tank by flushing the toilet.
3. Disconnect the old flapper by unhooking the two ears that are clipped to the pins on the sides of the flush valve.
4. Make sure to buy the correct size, as the replacement flappers come in both 2-inch and 3-inch sizes.
5. Install the new flapper by clipping both of the ears to the flush valve pins.
6. Turn the water supply back on and run the food color test after 15 minutes to see if the job was successful, i.e., if no color appears in the tank.

💡 Pro Tip: Moen toilets have a lifetime warranty on the internal parts. If your Moen toilet is running and you have the model number handy, before buying a new part consider calling the Moen customer service at 1-800-289-6636. They often provide a free flapper. This should only take 5 minutes.

Fix 2: Adjust or Replace the Fill Valve

If Test 3 has already indicated that the fill valve does not shut off even if the float is manually raised, then the fill valve has to be replaced.
Replacement is a 15-minute job that requires one tool (adjustable wrench) and costs $10-$15.
The Fluidmaster 400A is the most popular fill valve replacement, suitable for 95% of US toilets, with a 5-year warranty.
It can be purchased at any Home Depot store for about $12.

1. Turn off the water supply and flush to empty the tank
2. Sponge out remaining water from the tank bottom
3. Disconnect the supply line, i.e., the braided hose between the wall and the tank; have a towel ready
4. Unscrew the locknut under the tank, turning it counterclockwise by hand. Pull out the old fill valve.
5. Adjust height on new Fluidmaster 400A. Twist top section of fill valve to adjust height, per instructions.
6. Insert new fill valve, hand-tightening locknut under tank. Turn locknut another quarter turn with wrench. That is all.
7. Reattach supply line and refill tube. Clip refill tube into top of overflow tube.
8. Slowly turn on water. Check for leaks at base of fill valve and supply line.
9. Adjust water level. Set so it fills 1 inch below top of overflow tube.

⚠️ Important: Don’t over-tighten the fill valve locknut on the underside of the tank. A quarter turn after hand-tightening is enough. Over-tightening cracks the plastic locknut or worse, cracks the tank itself. This is an expensive repair. The locknut does not need to withstand structural stresses. It simply must be watertight.

Fix 3: Lower the Float

If water was running into the tube during Test 2 but shuts off during Test 3, then the float was simply set too high. This is a free fix and only takes about 30 seconds.
Ball Float (older toilets)
Look for an adjustment screw where the float arm attaches to the fill valve. Turn this screw counterclockwise to lower the float arm. Or, simply try bending the float arm slightly downward with your hand. Flush and observe the refill process. Adjust so that the water shuts off about 1 inch below the top of the overflow tube.

Cup Float (modern toilets)

Pinch the adjustment clip on the side of the float cup and move it down the fill valve shaft. Lower the float cup = lower water level. Let go to secure. Flush and check. Repeat the process until the water fills 1 inch below the top of the overflow tube.
💡 Pro Tip: Once the water level is set correctly, use a permanent marker to mark the spot inside the tank. A line at the correct height means you now have a quick reference point for future adjustments without having to measure the water level again.

Running Toilet Symptom Quick Reference Table

Match your symptom to the right fix before buying any parts:

Symptom	Cause	Test	Fix	Part Cost
Color in bowl without flushing	Worn flapper	Food coloring test	Replace flapper	$4–$8
Water runs into overflow tube	Float too high	Visual — water at tube rim	Lower the float	$0
Runs even with float lifted	Faulty fill valve	Lift float by hand	Replace fill valve	$10–$15
Weak flush and running	Chain too short or tangled	Check chain slack	Adjust flapper chain	$0
Intermittent random running	Slow flapper leak	Food coloring — wait 30 mins	Replace flapper	$4–$8

How to Read Your Water Meter to Confirm the Fix

Once you’ve done this, you’ll want to make sure that your repairs were successful, not just by listening for the water, but also by looking at your water meter. This is the ultimate way to make sure that your toilet has really stopped wasting water.

1. First, you’ll need to find your water meter, which is usually located near the street in a little box buried in the ground, or in your basement or utility room.
2. Next, make sure that all the water is turned off in your home – no water is running anywhere in your home. This means no appliances, no faucets, nothing.
3. Then, read your water meter and make a note of the numbers. You could also take a picture of your water meter with your phone.
4. After that, don’t use any water for 15 minutes – don’t flush your toilets, don’t turn on any faucets, etc.
5. Finally, read your water meter again – if the numbers have changed, that means that water is still running somewhere in your home, but if they are the same, you’ve successfully fixed your toilet.

🔑 Key Insight: Many water utilities offer apps or online portals through which you can view your hourly usage. If this is the case for your utility, take advantage of it. You can use it to precisely identify when the toilet was running and when the repair ended the waste. It can also be helpful in identifying future leaks you might otherwise not notice.

Common Mistakes Beginners Make

. Buying the Wrong Flapper Size
Flappers come in different sizes, namely 2 inches and 3 inches, and the wrong size will mean that the repairs will not work. The flapper will not cover the flush valve properly (it will continue leaking), or, on the contrary, will be too large and thus will not fit properly (it will continue leaking). It is very important that you take the old flapper with you when you go to buy a new one, so that you get the right size, or check your toilet model for a recommended flapper size from the manufacturer.

2. Too Much Chain Slack on the New Flapper
   Too much slack on a new flapper will mean that the flapper does not lift properly when you flush, which will result in a weak flush. Too little slack will mean that the chain will get caught underneath the flapper, which will not allow the flapper to close properly, and your toilet will continue running. You will need half an inch of slack between the handle arm and the flapper when they are in a resting position.

. Not Confirming the Fix With the Food Coloring Test
Most people, after replacing the flapper, will flush the toilet once, listen to the silence, and say, “Ah, that did the trick!” Not so fast, my friend. A brand-new, not perfectly seated, flapper can have a very slow leak, so slow that you don’t even know it’s leaking, but fast enough to waste hundreds of gallons of water per month. Run the food coloring test after replacing the flapper.

4. Using In-Tank Cleaning Tablets
   Those little blue tablets that you put in the tank, which turn the water in the toilet bowl blue, may give the toilet bowl a sparkling clean appearance, but they also destroy the rubber of the flapper 3 to 4 times faster than normal. The bleach and chemicals in these tablets are the culprit that destroys the rubber of the flapper. If you want to give your toilet bowl that sparkling clean look, use a toilet brush and some cleaner. Do not put these tablets in the tank.

5. Ignoring a Running Toilet Because It Seems Minor
   A running toilet is a common occurrence, and it is easy to ignore it because it is not a major problem. The cost, however, is quite different. A running toilet wastes about 200 gallons of water per day, translating into a cost of about $365 per year. Replacing a toilet flapper costs about $6, making it obvious that fixing it immediately is the right decision. Every day spent not fixing it is like throwing money away.

When to Call a Plumber

Running toilet repairs are safe for beginners in almost every instance. You should call a plumber if:
⦁ The toilet continues to run after replacing the flapper and the fill valve. The flush valve seat may be cracked and need to be replaced by the entire flush valve assembly.
⦁ You see cracks in the porcelain tank. Do not attempt to repair a cracked tank. You should replace it.
⦁ Water is accumulating at the base of the toilet. The wax ring seal has failed. The toilet must be removed and replaced.
⦁ The toilet runs and makes a banging noise while refilling. The banging noise is a water hammer caused by a faulty supply line, which is a separate issue from the running toilet.

Final thoughs

A running toilet is the most common and silently expensive running issue in American homes. The explanation for the fact that so many people suffer from this condition for longer than necessary is the fact that it appears to be a complicated procedure, and the fact is, it’s not.
It only takes 15 minutes and food coloring from your kitchen to identify the condition. The most common solution to the condition only takes 5 minutes and costs $6. The second most common solution to the condition does not cost anything and only takes 30 seconds. Even the most complicated solution to the condition only takes 15 minutes and $12.
You should run the food coloring test on all the toilets in your house today. The one you thought was fine may be the one running away with the money.