Fix a Running Toilet That Won't Stop

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The insight most people miss: a running toilet wastes up to 200 litres of water per day — but 95% of cases are fixed with a $5–15 part in under 30 minutes. There are exactly three culprits, and you can diagnose which one in 60 seconds.

60-Second Diagnosis

1. Remove the tank lid and look inside while the toilet runs.
2. Water spilling into overflow tube? → Float is set too high (fix A).
3. Flapper visibly open or water trickling into bowl? → Bad flapper (fix B).
4. Water level fine but still running? → Faulty fill valve (fix C).

Fix A — Adjust the Float ($0, 2 min)

1. If you have a ball float (round ball on arm): bend the arm down slightly or turn the adjustment screw clockwise.
2. If you have a cup float (cylinder on fill valve): pinch the clip and slide it down the shaft.
3. Target water level: 2–3 cm below the top of the overflow tube.

Fix B — Replace the Flapper ($5–10, 15 min)

1. Shut off water at the valve behind/below the toilet.
2. Flush to empty tank.
3. Unhook the old flapper from the pegs on the overflow tube and detach the chain from the handle arm.
4. Snap on the new flapper, attach chain with 1–2 cm of slack (too tight = always leaking, too loose = won't seal).
5. Turn water back on, wait for tank to fill, listen.

Fix C — Replace the Fill Valve ($10–15, 20 min)

1. Shut off water, flush, sponge out remaining water in tank.
2. Disconnect supply line from tank bottom, unscrew the locknut underneath.
3. Pull out old valve, drop in new Fluidmaster 400A (the industry standard — fits virtually all toilets).
4. Adjust height per instructions, reconnect supply line, turn water on slowly.
5. Set water level by turning the top of the valve.

Still running after all three fixes? The flush valve seat (where the flapper seals) may be cracked or corroded. Run your finger around the seat — if it feels rough or pitted, the seat needs replacing or the whole flush valve assembly needs swapping. At that point, a plumber visit costs $80–150 CAD and may be worth it.

Pro tip: Add a few drops of food colouring into the tank and don't flush for 15 minutes. If colour appears in the bowl, your flapper is leaking even if it looks fine — mineral buildup can warp rubber flappers invisible to the eye. Replace it regardless.