A running toilet is the most expensive small plumbing problem in a house. It is not dramatic, nothing floods, and it can quietly waste a startling amount of water — enough to show up on a Newnan water bill and enough that people often blame a leak somewhere they cannot find.
The good news is that the cause is almost always one of three parts, all of them inexpensive, and diagnosing which one is a five-minute job.
The dye test tells you which half of the problem you have
Take the tank lid off. Put a few drops of food colouring, or a dye tablet, into the tank — not the bowl. Then leave it alone for twenty or thirty minutes without flushing.
- Colour appears in the bowl — the flapper is leaking. Water is escaping from the tank into the bowl, the tank level drops, and the fill valve keeps topping it up. This is the most common cause by a wide margin.
- No colour in the bowl but the toilet still runs — the fill valve or the float is the problem, or water is going over the overflow tube.
That one test splits the diagnosis in half.
Cause 1: the flapper
The flapper is the rubber seal at the bottom of the tank. Over a few years it hardens, warps or develops mineral buildup, and stops sealing.
Signs it is the flapper: the toilet refills briefly every few minutes with nobody touching it, sometimes called phantom flushing. Dye test shows colour in the bowl.
- 1Shut off the supply at the valve behind the toilet and flush to empty the tank.
- 2Unhook the flapper from the chain and lift the ears off the overflow tube pegs.
- 3Take it to the store and match it. Flappers are not universal — get the same style.
- 4Wipe the seat it sits on. Mineral deposits and grit on the seat will make a brand-new flapper leak.
- 5Fit the new one and set the chain with a small amount of slack — about half an inch. Too tight and it holds the flapper open; too loose and it tangles under it.
Cause 2: the fill valve
The fill valve refills the tank after a flush and shuts off at the right level. When it fails it either never fully shuts off, or it hunts — cycling on and off repeatedly.
Signs: dye stays in the tank, but you hear a hiss or trickle continuously, or the toilet turns itself on and off in short bursts.
Fill valves are inexpensive and the modern replacements are straightforward: shut off the water, drain the tank, disconnect the supply line, unscrew the retaining nut underneath, drop the new valve in, reconnect and set the height.
Cause 3: the water level is too high
If the water level sits above the top of the overflow tube, water runs continuously down the tube into the bowl. The fill valve never senses a full tank so it never shuts off.
The fix is to lower the float. On modern column-style fill valves that means pinching a clip and sliding the float down; on older ball-and-arm assemblies it is an adjustment screw or bending the arm.
Target the water line about an inch below the top of the overflow tube, or at the mark stamped inside the tank.
Less common causes
- A cracked overflow tube — water escapes below the normal line.
- A warped or worn flush valve seat that a new flapper cannot seal against. This means replacing the whole flush valve, which requires pulling the tank.
- A flapper that is the wrong size for the flush valve — very common after a well-meaning repair.
- Hard water buildup on every rubber component. Coweta County water is hard enough that this shortens the life of flappers and seals noticeably. See our guide on hard water signs and solutions.
When to replace the whole toilet
If you are repeatedly replacing parts, if the tank or bowl is cracked, if the toilet is a pre-1994 high-volume model, or if the flush valve seat is pitted, the economics favour a new toilet. A modern unit uses considerably less water per flush and the parts are standard and cheap for the next twenty years.
Get it fixed
Most running toilets are a fifteen-dollar part. If yours has already had two parts thrown at it and still runs, something else is going on — Wright Way Services handles it across Newnan, Peachtree City, Fayetteville, Senoia and the rest of Coweta and Fayette County. Call (770) 301-4638.
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