Introduction
A running toilet can waste up to 200 gallons of water per day, which adds up fast on a NYC water bill — especially if your building sub-meters individual units. The constant sound of running water is also a common source of noise complaints in apartment buildings. Most running toilet issues are caused by a faulty flapper, a misadjusted float, or a worn-out fill valve, all of which are inexpensive parts you can replace yourself in under an hour with no special skills required.
Step-by-Step Instructions
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Step 1 Diagnose the Problem
Remove the tank lid and set it somewhere safe on a towel (porcelain lids are heavy and crack easily on tile floors). Flush the toilet and watch what happens. If water keeps flowing into the bowl after the tank refills, the flapper is not sealing properly. If the water level rises above the overflow tube, the float or fill valve needs adjustment. Drop a few drops of food coloring into the tank — if color appears in the bowl without flushing within 15 minutes, you have confirmed a flapper leak.
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Step 2 Adjust the Float Level
The float controls when the fill valve shuts off. If the water level is above the overflow tube, the float is set too high. For a ball float on a metal arm, gently bend the arm downward about half an inch. For a cup-style float on the fill valve column, pinch the spring clip and slide the float down the rod about an inch. Flush and observe — the water should stop filling about one inch below the top of the overflow tube. Adjust incrementally until you get it right.
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Step 3 Replace the Flapper
Turn off the water supply valve behind the toilet and flush to empty the tank. Unhook the old flapper from the pegs on either side of the overflow tube and disconnect the chain from the flush lever. Bring the old flapper to the hardware store to match the size — toilets in NYC buildings use various sizes and some older models require specific flappers. Install the new flapper by snapping it onto the pegs and reconnecting the chain with about half an inch of slack.
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Step 4 Check and Adjust the Chain
An improperly sized chain is a surprisingly common cause of running toilets. If the chain is too short, it holds the flapper partially open. If it is too long, it can get caught under the flapper and break the seal. With the lid off, flush and watch the chain action. It should have about half an inch of slack when the flapper is closed. Trim excess chain length with wire cutters to prevent it from tangling or snagging on the flush mechanism.
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Step 5 Replace the Fill Valve if Needed
If adjusting the float and replacing the flapper do not solve the problem, the fill valve itself may be worn out. Turn off water and flush the tank. Place a towel under the tank and disconnect the water supply line. Unscrew the lock nut under the tank and remove the old fill valve. Install the new one according to the manufacturer's instructions, adjusting the height to sit about one inch above the overflow tube. Reconnect the supply line and turn the water back on slowly.
When to Call a Professional
Call a plumber if the toilet continues running after replacing the flapper and fill valve, as the flush valve seat at the bottom of the tank may be warped or corroded — replacing it requires removing the entire toilet. Also call a pro if you notice water leaking from the base of the toilet, cracks in the porcelain tank, or if the shut-off valve behind the toilet is seized and will not turn. In NYC co-ops and condos, a leaking toilet can cause water damage to units below, so act quickly.
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