Toilet keeps running after flush

Toilet tank running continuously after a flush.

Quick Answer:

If the toilet keeps running after the normal refill, stop the water at the shutoff valve and lift the tank lid to watch the water level. Most often the cause is either water overflowing into the overflow tube because the float is set too high, or water leaking past a worn flapper. A few basic checks and a short adjustment will often stop the waste immediately.

Why This Happens

  • Float set too high — the fill valve keeps adding water until it pours into the overflow tube.
  • Worn or misseated flapper — water slowly leaks from the tank into the bowl after the flush.
  • Faulty fill valve or refill tube — these can cause continuous trickle or rapid refill.
  • Chain or lever problems — a short chain can prevent the flapper from sealing; a snagged lever can keep it open.
  • Mineral deposits or debris — buildup can stop parts from seating properly.
  • If you want a quick comparison with other common patterns, you may find the phrase Toilet won’t stop filling useful when deciding whether the issue is overflow-related or a fill-valve fault.

Step-by-Step What to Do

Step 1 — Stop the water and prepare

  • Turn the shutoff valve clockwise (behind the toilet near the floor) to stop incoming water.
  • Flush to drain most of the tank water so you can work and see parts clearly.
  • Set the lid on a towel or a stable surface to avoid chipping it.

Step 2 — Lift the tank lid and watch the water level

  • With the tank partially drained, watch the water as the tank refills after a test flush.
  • Confirm whether it’s running into the overflow tube or leaking into the bowl — both are visible when you watch the refill.
  • If water is continuously flowing into the overflow tube, the float or fill valve is the likely cause.

Step 3 — Check the flapper and chain

  • Inspect the flapper for cracks, warping, or mineral buildup. Press it closed and see if the leak stops.
  • Ensure the chain has a little slack; if it’s too tight it can hold the flapper slightly open. If it’s tangled, free it.
  • If the flapper is damaged, replace it — they are inexpensive and simple to swap out.

Step 4 — Adjust the float to stop just below the overflow

  • If the water level reaches or pours into the overflow tube, lower the float so the refill stops with the water line a small margin below the top of the overflow tube.
  • How to adjust depends on float type:
    • Ball float on an arm: bend the arm down slightly or turn the adjustment screw on the fill valve.
    • Float cup: move the clip or turn the adjustment rod on the fill valve to lower the cup.
  • Turn the shutoff back on, let the tank refill, and confirm the level now stops below the overflow.

Step 5 — Test and finish

  • Put a few drops of food coloring in the tank (not bowl) and wait 10–15 minutes. If colored water appears in the bowl without flushing, the flapper is leaking.
  • If adjustments fixed the issue, replace the lid and monitor usage over the next day to ensure the running stopped.
  • If water still runs, consider replacing the fill valve or flapper assembly depending on which part failed the tests.

What Not to Do

  • Don’t ignore continuous running—wasted water adds up fast.
  • If you can’t identify whether it’s overflow vs flapper leak, a plumber is appropriate.
  • Don’t force or over-tighten plastic parts — that can crack the valve or tank fittings.

When to Call a Professional

  • When you can’t determine whether the leak is into the overflow tube or through the flapper despite the tank check.
  • If replacing the flapper or adjusting the float doesn’t stop the running, and the fill valve leaks or won’t seat.
  • If the tank or internal parts are cracked, corroded, or the shutoff valve leaks — these may need a licensed plumber.
  • If the problem started after recent work and the toilet still runs, consider that a more complex installation fault — for example, a persistent issue after a recent repair like a Running toilet after replacing flapper.

Safety Notes

  • Turn off the water supply before working inside the tank to avoid unexpected sprays or overflows.
  • Place the tank lid on a soft, stable surface — it’s heavy and can chip or break if dropped.
  • Don’t use harsh chemical cleaners or drain additives in the tank; they can damage rubber parts like flappers and gaskets.
  • Wear gloves if you’re handling corroded parts or silt from the tank.

Common Homeowner Questions

  • Why is my toilet still running after I flush? Usually a flapper leak or float set too high — watch the tank to see which.
  • Can I fix a running toilet myself? Yes, many homeowners can fix it by adjusting the float or replacing the flapper.
  • Will a running toilet increase my water bill? Yes — even a small continuous leak can waste dozens to hundreds of gallons per day.

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