Is water running into the overflow tube?
Lower the float a small amount and flush once. Water that still climbs into the tube points to the fill valve.
Toilet troubleshooting
Toilet Keeps Running? Check the Flapper and Fill Valve
If your toilet keeps running, start with the tank open. A steady run is usually a leaking flapper, a chain holding the flapper open, water spilling into the overflow tube, or a fill valve that will not shut off.
A dry overflow tube points toward the flapper or chain. Water entering the overflow tube points toward the float setting or fill valve.
Watch one refill cycle before touching parts. The water path tells you what to test next.
Don’t start with: Do not buy a whole tank kit or bend parts until the tank shows the clue. Check whether water is entering the overflow tube, leaking past the flapper, or being held open by the chain.
Tank full but still running?Look for water slipping past the toilet flapper into the bowl.
Water reaching the overflow tube?Check the toilet fill valve and float setting before replacing anything.
Do this first
- Set the tank lid on a towel or solid floor space before you work inside the tank.
- Find the toilet shutoff valve before moving parts. Close it if the bowl or tank water is rising where it should not.
- Stop if the shutoff valve will not turn, will not stop the water, or starts leaking at the stem.
- Do not force old plastic nuts, tank bolts, or brittle valve bodies. Cracked porcelain turns this into a larger plumbing repair.
- Use clean water only inside the tank. Do not mix cleaners, tablets, or chemicals into a repair test.
- Call a licensed plumber if the tank or bowl is cracked, water is reaching the floor, or the toilet begins leaking at the base after tank work.
Last reviewed: 2026-06-19
60-second running-toilet sorter
Is the overflow tube dry while the bowl ripples?
Test the flapper. Tank water is slipping into the bowl even though the tank is not overfilling.
Does jiggling the handle change the sound?
Check the chain and trip lever before buying parts. The chain may be too tight, twisted, or caught under the flapper.
Does the toilet refill by itself every few minutes?
Run the dye test. Intermittent refill usually means the tank slowly leaks past the flapper or flush valve seat.
Did a new flapper fail to stop the leak?
Inspect the flush valve seat for scale, nicks, warping, or a flapper style that does not match the toilet.
Is water outside the tank, at the supply, or near the floor?
Stop the running-toilet diagnosis and control the leak first. That is no longer just a tank-internals problem.
Look at the tank clues first
The useful clues are inside the tank: chain slack, flapper movement, final water level, and whether water reaches the overflow tube.
Before you buy anything
Do not buy a flapper, fill valve, flush valve, or full tank rebuild kit until one tank check points there. Match the exact toilet model, flush valve size, chain setup, and old part shape; similar-looking tank parts can seal poorly.
What is probably happening
A running toilet is a tank water-path problem. The tank is either losing water into the bowl, overfilling into the overflow tube, or being held open by the handle linkage.
- If the overflow tube is dry but the bowl ripples or the dye test colors the bowl, tank water is slipping past the flapper or flush valve seat. The fill valve is only refilling what leaked out.
- A tight or tangled chain can hold the flapper up just enough to keep water moving after a flush.
- A float set too high lets the tank refill until water spills into the overflow tube.
- A worn fill valve may hiss, chatter, or keep climbing past the proper shutoff level even after the float is lowered.
- A rough flush valve seat can keep a new flapper from sealing, especially on older tanks with mineral scale.
What not to do first
The fastest bad repair is buying parts before you watch the water. Most running toilets give you a visible clue in the first minute with the lid off.
- Do not replace the whole toilet because the tank keeps running.
- Do not bend the float arm or trip lever hard enough to stress the valve or porcelain.
- Do not keep jiggling the handle as the repair. It only tells you the chain, lever, or flapper needs a closer look.
- Do not buy a full rebuild kit until the shutoff valve works, the tank hardware looks safe to remove, and the water-path test shows more than one worn part.
- Do not clean the tank with bleach tablets or harsh chemicals during diagnosis. They can damage rubber parts and confuse the leak test.
- Do not ignore water on the floor. A floor leak is a different problem from water moving inside the tank.
Tank result map
Take the lid off, wait until the tank is full, and watch the overflow tube, flapper, chain, and bowl. One result should stand out before you remove anything.
- Set the lid aside first. Toilet tank lids are heavier and more brittle than they look.
- Use a flashlight if the tank water is dark or the overflow tube is hard to see.
- Flush once only if the tank is quiet when you arrive. Then watch the refill from start to finish.
| What you see | What it usually means | Next move |
|---|---|---|
| Water spills into the overflow tube | The tank is overfilling or the fill valve is not shutting off. | Lower the float slightly, flush, and watch the final water level. |
| Overflow tube is dry but the bowl ripples | Tank water is leaking past the flapper or flush valve seat. | Run the dye test before buying a flapper. |
| Chain stays tight after the flush | The chain or trip lever is holding the flapper open. | Free the chain and leave slight slack with the flapper closed. |
| Toilet refills briefly every few minutes | The tank is slowly losing water into the bowl. | Use food coloring in the tank and wait without flushing. |
| New flapper still leaks | The seat may be scaled, nicked, warped, or mismatched to the flapper. | Inspect the flush valve seat and match parts by toilet model. |
Run the flapper test without guessing
A flapper is cheap, but the test is cheaper. Use the dye result to decide whether the flapper belongs in the cart or whether the fill valve path deserves attention.
- Let the tank fill and stop as much as it is going to stop.
- Add a few drops of food coloring to the tank water.
- Wait 10 to 15 minutes without flushing. Keep the handle alone during the test.
- Colored water in the bowl means tank water is passing the flapper or the flush valve seat.
- No color in the bowl while water enters the overflow tube points away from the flapper and back to the fill valve or float.
- Flush right after the test so dye does not sit against the porcelain.
Adjust the water level before replacing the fill valve
Overflow-tube water is a different failure than a flapper leak. Work the float setting first because a small adjustment can stop the run without opening the supply connection.
- Find the float on the fill valve and lower it a small amount. Many modern valves use a screw or sliding clip.
- Flush once and watch where the water stops. The final level should sit below the top of the overflow tube.
- If the water stops cleanly below the tube, the toilet needed adjustment rather than a new valve.
- If the level creeps upward after stopping, the fill valve is not holding shut.
- If the valve hisses, chatters, sprays, or ignores the float setting, replacement is more likely.
- Close the shutoff valve before any fill valve replacement, and stop if that valve will not fully stop the water.
When the repair points to parts
Buy the smallest part the test actually points to, then retest the tank. Use the dye result, overflow-tube water level, chain slack, and old-part shape before you add anything else to the cart.
- Buy a flapper only after a positive dye test, visible wear, or a press-down test that stops the run.
- Buy a fill valve only when water enters the overflow tube after adjustment or the valve will not shut off cleanly.
- Buy a replacement flush valve only after the dye test still reaches the bowl with a correctly matched flapper, and you can see or feel a rough, cracked, warped, or scaled seat below it.
- Buy a trip lever only when the handle arm is bent, corroded, loose, or rubbing the tank so the chain cannot relax.
- Take a clear photo of the old part and model marking before shopping. Some toilet tanks use specific flapper shapes or flush valve sizes.
- After any part swap, watch several flushes and then wait 15 to 20 minutes for a silent refill.
Tools You May Need
These support the tank checks on this page. Skip tool work if the shutoff valve fails, the tank is cracked, or old hardware starts breaking.
Food coloring or toilet dye tablets
Helps when: Confirms whether tank water is leaking into the bowl before you buy a flapper.
Skip it when: The overflow tube is visibly taking water; handle the water-level or fill-valve branch first.
Compare toilet dye tablets on Amazon
Inspection flashlight
Helps when: Makes the overflow tube, chain path, flapper edge, and fill valve shutoff point easier to see.
Skip it when: You already have clear light in the tank and can see the water path without leaning awkwardly.
Compare inspection flashlights on Amazon
Adjustable pliers
Helps when: Helps loosen a fill valve nut or supply connection after the water is shut off.
Skip it when: Plastic nuts are brittle, seized, or mounted through porcelain that already shows cracking.
Compare adjustable pliers on Amazon
Towels and sponge
Helps when: Catches tank water and dries the floor or bowl area so a fresh leak or ripple stands out.
Skip it when: Water is actively reaching the floor and the shutoff valve will not control it.
Compare towels and sponges on AmazonAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Replacement Parts
Parts come after the clue. Match the exact toilet model when you can, and compare the old part before assuming a universal piece will seal correctly.
Toilet flapper
Helps when: The dye test sends color into the bowl, the flapper is warped or stiff, or pressing it down stops the run.
Skip it when: Water is entering the overflow tube or the chain is holding the flapper open.
Compare toilet flappers on Amazon
Toilet fill valve
Helps when: The tank overfills into the overflow tube after float adjustment, or the valve keeps hissing and will not shut off.
Skip it when: The overflow tube stays dry and the dye test shows a flapper or flush-seat leak.
Compare toilet fill valves on Amazon
Toilet flush valve
Helps when: A correctly matched new flapper still leaks because the seat below it is rough, damaged, or warped.
Skip it when: The old flapper has not been tested yet, or the tank hardware is too brittle to remove safely.
Compare toilet flush valves on Amazon
Toilet trip lever
Helps when: The handle arm is bent, loose, corroded, or rubbing so the chain cannot go slack after a flush.
Skip it when: The handle moves freely and the chain already has slight slack when the flapper is closed.
Compare toilet trip levers on AmazonAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
FAQ
Why does my toilet keep running after I flush?
Most often, the toilet flapper is not sealing, the chain is holding it open slightly, or the toilet fill valve is letting water rise into the overflow tube. Watching the tank with the lid off will usually tell you which one it is.
How do I know if the toilet flapper is bad?
A dye test is the easiest check. Put a few drops of food coloring in the tank and wait 10 to 15 minutes without flushing. If color shows up in the bowl, the toilet flapper is leaking or the flush valve seat is not sealing.
Why is water going into the overflow tube?
That means the tank water level is too high or the toilet fill valve is not shutting off when it should. Try lowering the float first. If the water still climbs into the overflow tube, replace the toilet fill valve.
Can I just jiggle the handle and ignore it?
Watch the tank while you move the handle. If the chain tightens, the trip lever sticks, or the flapper finally drops flat, adjust that setup instead of using the handle as the repair.
What if I replace the toilet flapper and it still runs?
Then look closely at the flush valve seat. If it is rough, scaled, cracked, or warped, a new flapper may never seal well there. That is when a toilet flush valve replacement becomes the better fix.
Is a running toilet an emergency?
Usually not in the same way as a burst pipe, but it should not wait long. Open the tank and check whether water is rising toward the overflow tube. If the shutoff valve will not stop the water or the bowl starts overflowing, treat it as urgent and call a plumber.
Should I replace the fill valve or the flapper first?
Let the tank decide. Replace the flapper first only if the dye test sends color into the bowl or the flapper is visibly failing. Replace the fill valve first if water keeps rising into the overflow tube after the float is lowered.
Why does my toilet run only once in a while?
That usually means the tank slowly loses water and the fill valve refills it for a few seconds. Start with the dye test and the chain slack before you blame the fill valve.
How this page was built
Repair Riot built this page around visible tank clues: flapper leakage, chain slack, overflow-tube water, fill valve shutoff, and when a tank repair becomes a plumber call. The source links support leak-detection and toilet water-use context; the repair sequence is original guidance.
- EPA WaterSense Fix a Leak Week — supports household leak context, toilet dye testing, worn flappers, and when to consult a licensed plumber.
- EPA WaterSense Residential Toilets — supports residential toilet water-efficiency context and keeping toilet selection separate from a tank-parts repair.