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Why is my toilet running constantly?

A running toilet is a tank that cannot hold its water or cannot stop refilling — and it wastes a startling amount, up to 200 gallons a day. Every cause lives under the lid, which makes this the most DIY-friendly problem in plumbing.

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Snap a photo or describe what you see and the FinderlyFix assistant tells you what is likely going on, before you spend anything.

What it usually is

  1. A worn flapper leaking into the bowl

    The rubber flapper warps and lets tank water seep to the bowl; the fill valve tops it off in short bursts every few minutes. The food-coloring test proves it in fifteen minutes.

  2. A fill valve that will not shut off

    A fill valve past its prime keeps trickling; water climbs until it spills down the overflow tube and the sound never stops.

  3. Float set too high

    Water level above the overflow tube line means constant overflow — fixed with the float adjustment screw in one minute.

  4. A chain snagged or too tight

    A chain caught under the flapper, or with no slack, holds it fractionally open. The simplest fix on this page.

What you can check yourself

Lid off. Ten drops of food coloring in the tank, wait fifteen minutes without flushing: color in the bowl means flapper. Water at the overflow tube top means float or fill valve. Both parts are hardware-store standard — water off at the wall stop, and the swap is a screwdriver job.

When it’s a job for a pro

A toilet that still runs after new flapper and fill valve may have a cracked overflow tube or a degraded flush-valve seat — a plumber call, and on an old water-guzzler often the moment to price a modern toilet against the repair.

Parts are $10 to $30 DIY; a plumber visit for the same swap typically runs $100 to $250. The water bill from ignoring it can exceed both.

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