How to Fix a Running Toilet Without Calling a Plumber

That phantom flush. The constant hiss. The sound of water trickling long after everyone has left the bathroom. A running toilet is one of those household annoyances that's easy to ignore — until you open your water bill and realize it's been silently draining your wallet for weeks.

Here's the thing most people don't realize: a running toilet can waste up to 200 gallons of water per day. That's not a typo. Over the course of a month, you could be flushing away thousands of gallons and racking up a water bill that makes your eyes water more than the toilet does. If you're looking to reduce utility costs across the board, fixing this issue is just as important as other strategies to lower your water bill.

The good news? You can fix a running toilet yourself in under an hour, usually for less than $20 in parts. No plumber required. No special skills needed. If you can operate a pair of pliers, you've got what it takes.

In this guide, I'll walk you through exactly how a toilet works, how to diagnose what's causing yours to run, and four straightforward fixes that cover the vast majority of running toilet problems. Let's get your bathroom quiet again.

Understanding How Your Toilet Actually Works

Before you start tinkering, it helps to know what's going on inside that porcelain tank. Don't worry — toilet mechanics are surprisingly simple once you pop the lid off and take a look.

Every standard toilet has the same core components working together. When you press the flush handle, it lifts a chain connected to a rubber flapper at the bottom of the tank. That flapper opens, releasing water from the tank into the bowl, which creates the flush.

Once the tank empties, the flapper drops back down and seals the drain. The fill valve (that tall assembly on the left side of the tank) then kicks on and refills the tank with fresh water. As the water rises, a float — either a ball on an arm or a cup that rides up the fill valve — rises with it.

When the float reaches a preset level, it signals the fill valve to shut off. The overflow tube sits in the center of the tank as a failsafe. If the water level gets too high for any reason, excess water drains down this tube and into the bowl rather than flooding your bathroom floor.

That's it. Handle, chain, flapper, fill valve, float, overflow tube. When any one of these components malfunctions or falls out of adjustment, you get a running toilet.

How to Diagnose Why Your Toilet Won't Stop Running

Before you fix anything, you need to figure out which part is causing the problem. Here's a quick diagnostic process that takes about two minutes.

The Food Coloring Test

Remove the tank lid and drop a few drops of food coloring into the tank water. Don't flush. Wait 15 to 20 minutes, then check the bowl. If the colored water has seeped into the bowl without flushing, your flapper isn't sealing properly. This is the most common cause of a running toilet by a wide margin.

Listen and Watch

Flush the toilet and watch what happens inside the tank. Does the water keep running long after the tank is full? The float is probably set too high or the fill valve is faulty. Does water trickle continuously into the overflow tube? Again, your water level is too high or the overflow tube itself has an issue.

The Jiggle Test

Give the flush handle a little wiggle. If the running stops, the flapper chain is likely too tight or too loose, preventing the flapper from seating properly. This is the easiest fix you'll ever make.

Fix 1: Adjusting the Float to Fix a Running Toilet

If your diagnostic work points to water continuously flowing into the overflow tube, the water level in your tank is set too high. The fix is adjusting your float — and it takes about 30 seconds.

Ball Float (Older Toilets)

Older toilets use a rubber or plastic ball attached to a horizontal metal arm. To lower the water level, gently bend the float arm downward. Just a slight bend — maybe half an inch — is usually enough. Flush and see where the water level settles. It should sit about one inch below the top of the overflow tube.

If the arm won't bend easily or the ball has water sloshing around inside it (meaning it's waterlogged and not floating properly), it's time to replace it. They cost a couple of dollars at any hardware store.

Cup Float (Newer Toilets)

Most modern toilets use a cup-style float that slides up and down the fill valve shaft. You'll see a small adjustment clip or screw on the side. Squeeze the clip and slide the float downward to lower the water level, or turn the adjustment screw counterclockwise.

Again, aim for a water level about one inch below the overflow tube. Flush, watch the tank refill, and confirm the water stops at the right level. If it does, congratulations — you just saved yourself a plumber's visit.

This is one of those small fixes that can also help you cut your utility bills significantly when you're trying to trim household expenses across the board.

Fix 2: Replacing the Flapper

The flapper is the single most common reason toilets run. These rubber seals degrade over time. Minerals in the water, cleaning chemicals, and plain old age cause them to warp, crack, or develop a film that prevents a tight seal. If your food coloring test showed dye leaking into the bowl, the flapper is almost certainly your culprit.

Step-by-Step Flapper Replacement

Turn off the water supply. Find the shut-off valve behind and below the toilet (it's the oval-shaped handle on the wall or floor). Turn it clockwise until it stops. Then flush the toilet to drain the tank. If you've also got a dripping faucet, learning to fix a leaky faucet uses many of the same plumbing skills you're developing here.

Remove the old flapper. Most flappers simply unhook from the two pegs on either side of the overflow tube. Disconnect the chain from the flush lever arm and pull the old flapper free. Take it with you to the hardware store so you can match the size.

Install the new flapper. Hook the new flapper's ears over the same pegs on the overflow tube. Reconnect the chain to the flush lever. Here's the important part: make sure there's about half an inch of slack in the chain. Too tight and the flapper won't seal. Too loose and it won't lift fully when you flush.

Turn the water back on. Open the shut-off valve and let the tank refill. Flush a couple of times and watch to make sure the flapper seats firmly each time. Run the food coloring test again if you want to be thorough.

A universal flapper costs between $5 and $10. The whole job takes 10 to 15 minutes, even if you've never done it before.

Pro Tip: Clean Before You Replace

Sometimes the flapper itself is fine, but mineral buildup on the flapper or the flush valve seat is preventing a good seal. Before installing a new flapper, run your finger around the rim of the flush valve seat (the ring the flapper sits on). If it feels rough or gritty, scrub it with an old toothbrush and some white vinegar. This same kind of mineral buildup is what causes problems in other appliances too — it's similar to what happens when you need to deep clean your dishwasher to keep it running efficiently.

Fix 3: Fixing or Replacing the Fill Valve

If adjusting the float didn't solve the problem and the flapper is fine, the fill valve itself may be worn out. A faulty fill valve can run continuously, cycle on and off randomly, or make a loud humming or whining noise.

Try Cleaning It First

Modern fill valves have a cap on top that you can remove for cleaning. Turn off the water supply and flush to empty the tank. Then twist or pop the cap off the top of the fill valve (check your specific model — some twist, some have a screw).

Hold a cup upside down over the exposed valve and briefly turn the water supply back on. The pressure will flush out any debris clogging the valve. Replace the cap, turn the water on fully, and test.

Full Fill Valve Replacement

If cleaning doesn't help, replacing the entire fill valve is your next move. This sounds intimidating but it's genuinely straightforward.

Shut off the water and drain the tank. Flush and hold the handle down to drain as much water as possible. Use a sponge or old towel to soak up whatever's left in the bottom.

Disconnect the water supply line. Place a small bucket or towel under the connection at the bottom of the tank. Unscrew the supply line nut by hand or with pliers. Some water will drip out — that's normal.

Remove the old fill valve. Unscrew the lock nut on the outside bottom of the tank that holds the fill valve in place. Lift the old valve straight out.

Install the new fill valve. Most replacement fill valves (like the Fluidmaster 400A, which is practically the industry standard) are adjustable in height. Set it so the top of the overflow tube is about one inch below the critical level mark on the valve. Drop it into the hole, hand-tighten the lock nut from underneath, reconnect the supply line, and attach the refill tube to the overflow pipe.

Turn on the water and adjust. Let the tank fill and adjust the float level as described in Fix 1. The whole replacement takes about 20 to 30 minutes and a fill valve costs $8 to $15.

Fix 4: Checking and Fixing the Overflow Tube

The overflow tube is the open pipe in the center of your tank. It serves as a drain to prevent the tank from overfilling. But if this tube is cracked, too short, or damaged, it can cause continuous water flow into the bowl.

Signs of an Overflow Tube Problem

If water is constantly trickling down the inside of the overflow tube even after you've adjusted the float to the correct level, inspect the tube closely. Look for cracks, especially near the base where it connects to the flush valve assembly.

A cracked overflow tube means you'll need to replace the entire flush valve assembly — which is a bigger job. The flush valve is the unit the flapper attaches to, and it's sealed to the bottom of the tank with a large gasket. Replacing it requires removing the tank from the bowl.

When the Tube Is Too Short

In rare cases, a previous repair might have left you with an overflow tube that's been cut too short. If the tube sits below the waterline no matter how much you lower the float, water will perpetually flow over the top. The fix here is replacing the flush valve assembly with one that has the correct overflow tube height for your toilet model.

This is one of the few running toilet repairs that starts to border on "maybe call a professional" territory, especially if you're not comfortable removing the tank. But if you're handy and patient, it's still a doable DIY project — just set aside about an hour.

Tools and Materials You'll Need

One of the best things about toilet repair is how few tools are required. Here's your complete shopping list for tackling any of the fixes above.

Tools:

• Adjustable pliers or a small wrench
• A flathead screwdriver
• An old toothbrush (for cleaning mineral deposits)
• A sponge or old towels
• A small bucket
• Food coloring (for diagnosis)

Replacement Parts (as needed):

• Universal toilet flapper ($5 to $10)
• Fill valve replacement kit ($8 to $15)
• Flush valve assembly ($15 to $25, only if overflow tube is damaged)
• Toilet repair kit — all-in-one ($20 to $25, covers flapper, fill valve, and hardware)

My recommendation: just grab a universal toilet repair kit. For about $20, you get every part you might need, and you'll have spares for next time. Think of it as a small investment — the same kind of practical, money-saving mindset that helps when you're trying to remove water stains from wood furniture yourself instead of paying a refinisher.

When to Actually Call a Plumber

I'm a big advocate for DIY fixes. Most running toilet problems are genuinely simple to solve, and there's real satisfaction in handling it yourself. But there are a few situations where calling a professional is the smart move.

The toilet is cracked. If you notice a crack in the porcelain tank or bowl, stop. A cracked toilet can't be reliably repaired and needs to be replaced. Water damage from a cracked tank can get expensive fast.

You've tried everything and it still runs. If you've replaced the flapper, adjusted the float, installed a new fill valve, and checked the overflow tube — and the toilet is still running — there may be an issue with the flush valve seat or the tank-to-bowl gasket that requires more advanced work.

There's water on the floor. A running toilet and water pooling around the base are two different problems. Water on the floor could indicate a failed wax ring seal, a cracked tank, or a loose tank-to-bowl connection. These repairs are more involved and a misdiagnosis can cause serious water damage.

You're not comfortable working with plumbing. There's no shame in calling a pro. A plumber will typically charge $100 to $250 to fix a running toilet, parts included. If that buys you peace of mind, it's money well spent.

How to Prevent Your Toilet From Running in the Future

Once you've fixed the problem, a little maintenance goes a long way toward preventing a repeat.

Replace flappers proactively. Flappers typically last 3 to 5 years. If yours is getting stiff, discolored, or warped, swap it out before it starts leaking. It's a $7 part and five minutes of work.

Avoid drop-in tank cleaners. Those blue chlorine tablets you drop in the tank? They accelerate rubber degradation. They eat through flappers and gaskets much faster than plain water. If you want to keep your bowl clean, use a toilet bowl cleaner applied directly to the bowl instead.

Check your water pressure. Excessively high water pressure (above 80 PSI) can stress toilet components and cause premature wear. If you suspect high pressure, a simple gauge that threads onto a hose bib costs about $10 and takes seconds to read.

Do an annual tank check. Once a year, pop the lid off your toilet tanks and look inside. Check for mineral buildup, test the flapper seal, and make sure the float is at the right level. Two minutes of inspection can save you months of wasted water.

Frequently Asked Questions

Why does my toilet run intermittently instead of constantly?

This is called "phantom flushing" and it's almost always caused by a slow leak past the flapper. The flapper lets water seep from the tank into the bowl gradually. When the water level drops enough, the fill valve kicks on briefly to top off the tank. Replace the flapper and this cycle will stop.

Can a running toilet increase my water bill significantly?

Absolutely. A toilet with a steady leak can waste 200 gallons per day — that's over 6,000 gallons a month. Depending on your local water rates, that can add $50 to $200 or more to a single monthly bill. Even a small, slow leak adds up over time. Fixing it promptly is one of the easiest ways to save money at home.

How do I know what size flapper to buy?

Most residential toilets use either a 2-inch or 3-inch flapper. The easiest way to tell: look at the flush valve drain opening at the bottom of your tank. If it's about the size of a baseball, you need a 2-inch flapper. If it's closer to a softball, you need a 3-inch. When in doubt, take your old flapper to the hardware store and match it visually.

Is it OK to turn off the water supply to a running toilet as a temporary fix?

Yes, this is perfectly fine as a short-term measure. Turn the shut-off valve clockwise to close it. You'll need to manually turn the water on to refill the tank each time you flush, but it stops the waste immediately. Just don't forget to actually fix the underlying problem — this is a Band-Aid, not a solution.

Do I need to replace the whole toilet if it keeps running?

Almost never. Running toilets are caused by inexpensive, easily replaceable internal parts. Even if you need to replace the fill valve, flapper, and flush valve all at once, you're looking at maybe $40 in parts. A whole new toilet costs $150 to $500-plus installed. Replace the parts first — it solves the problem 95% of the time.

Wrapping Up: You've Got This

A running toilet sounds like a minor annoyance, but between the wasted water and the inflated bills, it's a problem worth solving right away. The best part is that you don't need any plumbing experience to handle it.

Start with the food coloring test to pinpoint the issue. In most cases, you'll be looking at a worn-out flapper that costs less than a fast food meal to replace. If it's the float, a 30-second adjustment solves it. Even a full fill valve replacement is a beginner-friendly job that takes less time than watching an episode of your favorite show.

Grab a basic toilet repair kit, set aside 30 minutes this weekend, and take care of it. Your water bill — and your sanity — will thank you.