A toilet that keeps running is usually caused by one of six tank parts failing to seal or shut off: a worn flapper, a faulty fill valve, a float set too high, a tangled chain, a damaged flush valve seat, or a refill tube pushed too deep. Most fixes take under 15 minutes with parts that cost less than $20 — but a running toilet can waste 200+ gallons a day, so don’t ignore it.
Why Does a Toilet Keep Running After Flushing?
Your toilet tank works on a simple cycle: the fill valve refills the tank after a flush, a float rises with the water and tells the valve to stop, and a rubber flapper seals the tank so the water stays put until the next flush. When any part of that cycle fails to seal or shut off, water keeps moving — either trickling past the flapper into the bowl, or spilling nonstop down the overflow tube. The sound you hear is the fill valve repeatedly topping the tank back up.
The two patterns tell you where to look:
- Runs constantly, never stops → water is going over the top of the overflow tube, or the fill valve never closes.
- Runs on and off by itself (“phantom flushing”) → water is leaking slowly past the flapper; every 15–30 minutes the level drops enough to trigger a refill.
Cause 1: Is Your Flapper Worn or Warped?
The flapper is the rubber stopper at the bottom of the tank that lifts when you flush and drops back to seal the flush valve. It’s the single most common cause of a running toilet. Greensboro’s chlorinated city water gradually makes the rubber stiff and brittle, and mineral scale builds up on the sealing edge until it can no longer hold water back.
Test: Lift the tank lid and press the flapper down firmly with a stick. If the running stops, the flapper isn’t sealing on its own — replace it.
Fix: Flappers are universal-fit and cost $5–$10. Match the size (most are 2-inch; newer low-flow toilets may use 3-inch), unhook the old one, snap the new one on, and reattach the chain with about half an inch of slack. No tools, no water shutoff needed beyond the toilet’s own valve.
If the flapper looks fine but the leak continues, the problem may be the surface it seals against — see Cause 5.
Cause 2: Is the Fill Valve Failing?
The fill valve is the tall assembly on the left side of the tank that lets water in after a flush. When its internal diaphragm wears out or gets clogged with sediment, it can’t close completely — water keeps hissing into the tank indefinitely, and the excess drains down the overflow tube.
Test: Lift the float gently by hand. If the water stops when you lift, the valve itself works but the float needs adjusting (Cause 3). If water keeps flowing even with the float raised, the valve is done.
Fix: Fill valve replacement is a $10–$15 part and a 20-minute job: shut off the toilet supply valve, flush to drain the tank, disconnect the supply line, swap the valve, and set the height so the waterline mark sits about an inch below the overflow tube. If your home is in an older Greensboro neighborhood like Fisher Park or Lindley Park with original galvanized supply lines, be gentle — corroded shutoff valves sometimes won’t reopen once closed. That’s a toilet repair and installation job best left to a pro.
Cause 3: Is Your Float Set Too High?
If the float is set too high, the tank overfills on every cycle and the surplus pours continuously down the overflow tube — the toilet technically never “fills,” so it never stops. This is the most overlooked cause because nothing is actually broken.
Test: Look at the water level in the tank. It should sit about ½–1 inch below the top of the overflow tube, at the marked waterline on the inside of the tank.
Fix: On a ball float, bend the float arm down slightly or turn the adjustment screw on top of the fill valve. On a cup-style float, squeeze the clip on the side of the shaft and slide the cup down half an inch. Flush once and confirm the water stops at the right level.
Cause 4: Is the Flush Chain Tangled or Too Tight?
The chain connecting the flush handle to the flapper needs a little slack — roughly half an inch. A chain that’s too short or has slipped under the flapper holds it slightly open forever. A chain that’s too long can kink or get caught under the flapper when it drops.
Test: Watch a flush with the lid off. The flapper should drop straight down and seat fully. If it lands crooked or the chain pulls it sideways, you’ve found it.
Fix: Re-hook the chain to a different link to set the slack, and make sure the excess chain can’t drift under the flapper. Takes 30 seconds.
Cause 5: Is the Flush Valve Seat Damaged?
Sometimes you replace the flapper and the toilet still runs. The culprit is the flush valve seat — the hard plastic or brass rim the flapper seals against. Years of chlorine exposure and mineral buildup pit and roughen that surface, so even a brand-new flapper can’t seal against it.
Test: Run your fingertip around the seat rim (water off, tank drained). If it feels rough, gritty, or chipped instead of smooth, the seat is the problem.
Fix: Light scale can sometimes be smoothed with fine emery cloth. A cracked or deeply pitted seat means replacing the flush valve assembly — a bigger job that involves removing the tank. For most homeowners this is where DIY ends and a professional toilet repair makes sense.
Cause 6: Is the Refill Tube Creating a Siphon?
The small refill tube should clip to the top of the overflow tube and end above the waterline. If it’s pushed too far down inside the overflow pipe, it creates a siphon that continuously draws water out of the tank — the fill valve cycles forever and no adjustment fixes it.
Test: Pull the refill tube out of the overflow pipe and clip it to the rim instead. If the running stops within a minute, that was it.
Fix: Trim or reposition the tube so its end stays above the tank waterline. Zero-cost fix, zero parts.
How Do You Run the Dye Test for a Silent Leak?
Not sure water is leaking into the bowl at all? Add a few drops of food coloring (or a dark drink) to the tank, don’t flush, and wait 15–20 minutes. If color appears in the bowl, tank water is bypassing the flapper or flush valve seat — 100% confirmation you have a leak, even if you never hear the toilet run. Silent leaks like this are also a top suspect when your water bill suddenly jumps — a toilet leaking 200 gallons a day adds up faster than any other fixture in the house.
How Much Water Does a Running Toilet Waste?
A moderately running toilet wastes 200 gallons per day or more; a wide-open fill valve can waste over 1,000. At Greensboro water and sewer rates, that’s roughly $30–$150 a month literally going down the drain — and unlike a dripping faucet, most of it is silent. If your bill spiked and nothing else changed, check the toilets first before assuming a hidden leak.
When Should You Call a Plumber for a Running Toilet?
Call a professional when:
- You’ve replaced the flapper and adjusted the float and it still runs (flush valve seat or deeper issue)
- The shutoff valve behind the toilet is corroded, stuck, or leaks when turned
- The toilet rocks, leaks at the base, or you see water staining on the floor or ceiling below (wax ring failure — a different, urgent problem)
- The toilet is old and parts are no longer standard
Call Plumbers of Greensboro at 877 708 6986 — toilet repairs are same-day in most cases across Greensboro, from Irving Park to Summerfield.
Frequently Asked Questions
Q: Why does my toilet run every few minutes but stop in between? A: That’s phantom flushing — water is leaking slowly past the flapper into the bowl. As the tank level drops, the fill valve kicks on briefly to top it up. The flapper (or the seat it seals against) is worn. The dye test confirms it in 15 minutes.
Q: Why is my toilet still running after I replaced the flapper? A: Usually the flush valve seat is pitted or scaled, so the new flapper can’t seal. Other suspects: chain too tight, refill tube pushed too deep into the overflow pipe, or a failing fill valve. Check those three before buying more parts.
Q: How much does it cost to fix a running toilet in Greensboro? A: DIY parts run $5–$20 (flapper or fill valve). Professional repair typically costs more but includes diagnosis of the whole tank assembly and a warranty on the work — and it stops a leak that can waste $30–$150/month in water.
Q: Can a running toilet increase my water bill a lot? A: Yes — it’s one of the most common causes of a sudden high water bill. A running toilet can waste 200–1,000+ gallons per day, often silently. Fix it fast, and if your bill is still high afterward, have the home checked for hidden leaks.
Q: Is a running toilet an emergency? A: Usually not — you can shut the toilet’s supply valve to stop the waste while you arrange a repair. It becomes urgent if water is leaking at the base, the shutoff valve won’t close, or you see ceiling/floor water damage below the bathroom.