A running toilet wastes hundreds of litres a day and is almost always one of three cheap parts: the flapper, the fill valve, or the float setting. Here is how to tell which, and fix it.
Riley Brand
Lift the tank lid and look. If water is trickling into the overflow tube (the open vertical pipe in the middle), the water level is set too high - that is a float adjustment. If the level looks right but the toilet hisses or refills randomly, do the dye test: a few drops of food coloring in the tank, wait 15 minutes without flushing. Color seeping into the bowl means the flapper is leaking.
Those two checks diagnose nearly every running toilet. The flapper - the rubber disc sealing the tank's drain hole - is the culprit in the large majority of cases, because rubber hardens, warps, and stops sealing after a few years of sitting in water.
Turn off the water at the shut-off valve behind the toilet (clockwise), flush to empty the tank, and unhook the old flapper: it unclips from two pegs on the overflow tube and its chain unhooks from the flush lever arm. Take it to the hardware store and match it - flappers vary by size (typically 2-inch or 3-inch) and mounting style.
Clip the new one on, attach the chain with just a little slack - about one chain link of droop when the flapper is seated. Too tight and the flapper cannot fully close; too loose and the chain gets trapped underneath it. Turn the water back on, let the tank fill, and flush a few times to confirm a clean seal and full flush.
The correct water level is about 2 to 3 centimeters (an inch) below the top of the overflow tube - most tanks have a marked fill line. On modern fill valves, the float is a cup that slides on the valve shaft: turn the adjustment screw or pinch the clip and slide the cup down to lower the level. On older ballcock valves with the arm-and-ball float, gently bend the metal arm downward.
If adjusting the float does nothing, or the valve hisses, cycles, or fills slowly forever, replace the fill valve itself - universal replacements cost about $12 to $15 and install in 20 minutes with the same shut-off-drain-swap sequence as the flapper, plus disconnecting the supply line at the tank's base.
Sometimes the fix is dumber than a part: a chain that is too long can tangle under the flapper and hold it open intermittently - the classic 'jiggle the handle' toilet. Shorten the chain. A loose flush handle that sags can also hold tension on the chain; tighten the nut inside the tank (note: it is reverse-threaded on most toilets - turn counterclockwise to tighten).
Mineral buildup on the flapper seat - the ring where the flapper lands - also breaks the seal. While the tank is empty, rub the seat smooth with a scouring pad. If the seat itself is pitted or corroded, repair seats that glue over the old one exist, though at that age a new flapper-and-seat kit is the better buy.
A silently leaking flapper wastes anywhere from a slow trickle to hundreds of litres a day; a visibly running toilet can pass over a thousand. On metered water, that is real money every month - the $10 flapper typically pays for itself within weeks. The dye test twice a year catches silent leaks before the bill does.
Know when it is not DIY: water on the floor (not in the tank), leaks from the tank bolts or the base of the toilet, or cracks in the porcelain are different problems - gasket and wax-seal territory, where a plumber visit beats experimentation, because the failure mode is a flooded floor.
That 'phantom flush' is a slow flapper leak: the tank loses water until the fill valve tops it up. Do the dye test to confirm, then replace the flapper - it is almost never anything else.
No, but match the size (2-inch versus 3-inch drain) and style. Take the old one to the store. Universal flappers fit most toilets; some modern high-efficiency models need a brand-specific part, listed in the tank or manual.
Check the chain slack and the water level next. If the level creeps above the overflow tube, the fill valve or float needs adjusting or replacing. If the flapper seat is rough with mineral deposits, scrub it smooth - a new flapper cannot seal against a pitted seat.
No - tank water is clean supply water, the same as the tap. It only becomes toilet water after it leaves the tank. Working in the tank with bare hands is fine.
