Last reviewed and updated: 2026-09-28
Put a few drops of food coloring in the toilet tank, wait twenty minutes without flushing, and look in the bowl. Color in the bowl means the flapper is leaking. The EPA reports that a stuck toilet fill valve can waste 4,300 gallons a day, and at Cobb County's top-tier water and sewer rates that is well over $1,000 in a month.
The dye test, step by step
- Lift the tank lid on the toilet, not the bowl.
- Add color. A few drops of food coloring, or a dye tablet if your utility supplies them. Enough to tint the water clearly.
- Wait twenty minutes. Do not flush. Do not let anyone else flush.
- Look in the bowl. Any color in the bowl means water is passing from the tank past the flapper, continuously, without the toilet ever making a sound.
- Repeat on every toilet in the house. The one that leaks is rarely the one you suspect.
A flapper costs a few dollars and takes about ten minutes to change. This is the one repair on this entire website that most homeowners can genuinely do themselves.
What a leaking toilet actually costs in Cobb County
The EPA's WaterSense figures give the volumes. Cobb's published 2026 rate schedule gives the price. Putting them together is what makes the number real:
| Leak | EPA figure | Roughly, at Cobb top-tier water + sewer |
|---|---|---|
| Average household leaks, all causes | 9,300+ gallons a year | About $175 a year |
| A faucet dripping once a second | 3,000+ gallons a year | About $56 a year |
| A silently leaking flapper | Thousands of gallons a year | $100 to $800 a year, depending on the seal |
| A stuck toilet fill valve | Up to 4,300 gallons a day | Over $1,000 in a single month |
The EPA also reports that nine percent of homes have leaks wasting 50 gallons or more per day, that household leaks waste close to a trillion gallons nationally each year, and that fixing the easily corrected ones saves the average household about 10% on its water bill.
Rather talk it through first?
No forms and no waiting for a callback. Speak to a technician, describe what you are seeing, and get a straight answer about what it takes to find it.
Why a toilet leak is invisible
A failing flapper does not run water into the room. It lets tank water slip into the bowl and down the drain, silently, hour after hour. There is no sound, no damp patch and nothing to see. The only evidence is the meter and the bill.
Two other toilet faults do the same thing:
- A fill valve that does not shut off, sending water down the overflow tube inside the tank. This is the 4,300-gallon-a-day failure.
- A float set too high, so the water level sits above the overflow and trickles into it permanently.
Lift the tank lid and look: if the water level is at or above the top of the overflow tube, that is your leak, and adjusting the float fixes it.
If the toilets are clean
Then the leak is somewhere you cannot see, and the order of checking goes from cheapest to most expensive:
- Run the meter test. Everything off, watch the low-flow indicator. Any movement means water is escaping.
- Isolate the irrigation. Close its supply and re-check. Underground, on a timer, at night is the classic missed cause.
- Split inside from outside. Close the main house valve. Still moving means the leak is in the buried service line.
- Look for the indoor signs. Running water with everything off, a warm patch on the floor, damp carpet, a musty smell.
The high water bill guide works through the whole sequence, and if the bill has already landed, the leak adjustment may recover part of it.
Document the repair even for a flapper. Cobb County accepts a parts receipt as proof of repair on a leak credit application. A three-dollar receipt from a hardware shop is a supporting document.
Where these figures come from
Everything above is taken from a published source. Rates, policies and conditions change, so check the date on each before relying on it.
- US EPA WaterSense, Fix a Leak Week: 9,300 gallons per household per year, 3,000 gallons from a one-drip-per-second faucet, 9% of homes wasting 50+ gallons a day, ~10% bill saving.
- US EPA WaterSense, Know Your Flow: A Guide to Leak Detection, 2026: a stuck toilet fill valve can waste 4,300 gallons per day.
- Cobb County Water System, Schedule of Rates, Charges and Fees, effective 1 June 2026.
Frequently asked questions
How do I know if my toilet is leaking?
Put a few drops of food coloring in the tank, wait twenty minutes without flushing, then look in the bowl. Color in the bowl means the flapper is letting water through. Also lift the lid and check the water level is below the top of the overflow tube.
How much water does a running toilet waste?
A silently leaking flapper wastes thousands of gallons a year. The EPA reports that a stuck fill valve can waste up to 4,300 gallons a day, which at Cobb County's top-tier water and sewer rates is over $1,000 in a single month.
Can a toilet leak without making any sound?
Yes, and that is the common case. A worn flapper lets tank water slip into the bowl and down the drain with no noise, no damp and nothing visible. The meter and the bill are the only evidence.
Will Cobb County credit a bill caused by a toilet?
A failed flapper or fill valve is normally an eligible plumbing failure, provided you can show proof of repair and the usage crossed the county's threshold of 150% of the same month a year earlier. A parts receipt counts as documentation.