Run the Test Right Now.
A toilet can lose water continuously without any visible dripping and without making any sound you would notice. The flapper — a rubber valve at the bottom of the tank — gradually wears out over time and begins allowing water to seep from the tank into the bowl between flushes. This is called a silent leak, and it is one of the most common sources of unexplained increases on a water bill. The EPA estimates that a leaking toilet flapper wastes an average of 200 gallons of water per day.
How to Run the Test
Source: EPA WaterSense Household Leak Detection Guide; Denver Water Fix a Leak Resources 2026.
If the Color Appears in the Bowl
A colored bowl confirms the flapper is not sealing properly. The repair is one of the most accessible home fixes available: a replacement flapper costs $5 to $15 at any hardware store and installs without tools in under 10 minutes. Bring the old flapper with you to the store — or take a photo of it — to match the correct size for your toilet model. Most hardware stores carry universal flappers that fit the majority of standard toilets.
When to Call a Plumber
If replacing the flapper does not stop the color from appearing in the bowl, the issue may be with the flush valve seat — the surface the flapper rests against. A scored or corroded seat cannot form a proper seal regardless of the flapper condition. This is still a relatively minor repair for a licensed plumber, but one that requires a bit more work than a simple flapper swap.
If the tank refills frequently on its own — even without anyone using the toilet — that is a reliable sign that water is escaping. The food coloring test simply confirms where it is going. Both symptoms point to the same solution: a flapper or flush valve that needs attention.
With care,
Mike Bridges
Founder, The O55 Report