The leak that never makes a puddle
Inside every tank toilet, a rubber flapper holds water in the tank and a fill valve refills it after each flush. When the flapper warps or the fill valve sticks, water trickles from the tank into the bowl and down the drain. The meter moves, the bill rises, and nothing anywhere looks wet.
Hard water speeds this up. Mineral deposits can keep a flapper from sealing and clog the fill valve, both common in Fullerton's blended groundwater supply. It is worth checking every toilet in the house before paying for leak detection.
The dye test
- Remove the tank lid.Set it somewhere safe; tank lids are heavy and crack easily.
- Add color.Put several drops of food coloring or a dye tablet into the tank water.
- Wait without flushing.Leave it for 15 to 20 minutes.
- Check the bowl.Any color in the bowl means water is leaking past the flapper.
- Flush to clear the dye.Flush once so the coloring does not stain the bowl.
What you see and what it means
| Symptom | Likely cause |
|---|---|
| Color shows in the bowl | Flapper not sealing, or a worn flush valve seat |
| Water running into the overflow tube | Fill valve set too high or failing to shut off |
| Toilet refills briefly on its own every so often | Slow flapper leak, sometimes called ghost flushing |
| Hissing sound from the tank | Fill valve not closing fully |
| Water on the floor at the base | Wax ring, bolts or supply connection, not an internal leak |
Do it yourself or call a plumber
Often a DIY fix
- Replacing a worn flapper
- Adjusting the float so water stays below the overflow
- Replacing a fill valve with the supply shut off
- Cleaning mineral buildup from the flapper seat
Worth a plumber
- Water on the floor around the base
- Cracked tank or bowl
- Corroded or stuck supply shutoff valve
- Leak shows on a ceiling below
Check every toilet
- Main bathroom
- Hall or guest bathroom
- Rarely used toilets, which often leak unnoticed
- Garage, pool house or ADU bathrooms
Common questions
Can a toilet leak really raise the bill a lot?
A steady leak runs all day, every day, so it can add noticeably to usage. The meter test and dye test together show whether it is a factor.
Will the dye stain my toilet?
Food coloring generally flushes away. Flush soon after checking the bowl to be safe.
I fixed the toilet but the meter still moves. Now what?
Then there is another leak. Continue with the house shutoff and water heater checks to narrow it down.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.