A Running Toilet Is the Most Expensive Sound in Your House

The dye test

Put a few drops of food coloring in the tank and don't flush for fifteen minutes. Color in the bowl means water is passing the flapper, and the fill valve is quietly topping the tank off around the clock.

The phantom flush

If the tank refills on its own when nobody has used it, the leak is fast enough to drop the float. That's not a quirk — it's a continuous leak.

What usually needs replacing

Most running toilets come down to a small number of parts, all of which wear on a predictable schedule.

• Flapper hardened or warped by age and by in-tank cleaning tablets
• Fill valve that no longer shuts off cleanly
• Chain adjusted too short, holding the flapper slightly open
• Water level set above the overflow tube, so it drains continuously

When it's not the flapper

Water on the floor at the base, rocking when you sit, or a stain on a ceiling below the bathroom points at the wax seal or the flange — a different repair, and one worth doing before the subfloor gets involved.