Toilet Keeps Running? Here Is Why, and the Fix

A running toilet is not a cosmetic annoyance - it is a continuously open tap on your water bill. The EPA's WaterSense program puts household leaks at nearly 1 trillion gallons of water wasted annually nationwide and the average household's leaks at more than 9,300 gallons a year, and it notes that nine percent of homes have leaks wasting 50 gallons or more per day. On toilets specifically, WaterSense says an old or worn flapper can cause a toilet to flush on its own or silently leak thousands of gallons a year.

The relevant part is that word silently. A toilet that hisses or refills every few minutes gets noticed. One with a flapper passing a thin film of water into the bowl makes almost no sound and shows up only on the bill - which is why plumbers check toilets first when a homeowner reports an unexplained increase.

The other reason to act quickly: these are inexpensive parts. A flapper, a fill valve or a complete tank rebuild kit are among the cheapest repairs in plumbing, and the water they stop wasting pays for them quickly.

Take the tank lid off, set it somewhere safe and flat, and watch what happens. Nearly every running-toilet diagnosis is visible from above.

1. Run the dye test. Put a few drops of food coloring in the tank, do not flush, and wait. If color appears in the bowl within about ten minutes, water is passing the flapper - that is your leak. This is the EPA WaterSense test and it is the single most useful check in the house.
2. Watch a full flush and refill. The flapper should drop and seal, the tank should fill to about an inch below the top of the overflow tube, and the fill valve should shut off cleanly and stay off.
3. If water is trickling into the overflow tube, the water level is set too high or the fill valve is not shutting off - adjust the float first.
4. If the flapper is not dropping flat, check the chain: too short and it holds the flapper open, too long and it tangles under it. There should be a little slack with the handle at rest.
5. Press the flapper down with a finger (the tank water is clean). If the running stops, the flapper or the seat it sits on is the problem.
6. Look at the flapper itself. If it is warped, stiff, slimy or has a mineral ring, it is done - they are consumable parts and hard water shortens their life.

Almost every running toilet is one of these three. All are homeowner-level repairs with the water shut off at the angle stop behind the toilet, and all of the parts are sold as universal kits.

• A worn flapper. The rubber loses flexibility and mineral deposits build on the seat, so it no longer seals. Replace the flapper, and wipe the seat clean while you are in there. This is the most common cause by a wide margin.
• A failed fill valve. It will not shut off completely, so the tank overfills into the overflow tube and the valve keeps running. Replacement is a single-part job: shut off the supply, drain the tank, unscrew the old valve, fit the new one, set the height and level.
• A misadjusted float or chain. The cheapest possible fix. Setting the water level to about an inch below the top of the overflow tube, and leaving a little slack in the chain, solves a surprising share of running toilets with no parts at all.
• Less common: a cracked overflow tube, a flush valve seat that is pitted beyond cleaning (which means a flush valve rather than a flapper), or a tank-to-bowl gasket that lets water pass internally.

Some symptoms look like a running toilet but are something else, and these are the ones not to patch with a new flapper.

• The toilet refills briefly every few minutes with nobody using it - a classic phantom flush, which is a flapper leak, but worth checking the tank-to-bowl connection too.
• Water on the floor around the base - a wax ring or a loose closet bolt, not a tank problem, and worth fixing before the subfloor suffers.
• The bowl level drops on its own - possibly a bowl leak or a venting problem rather than a tank leak.
• Several fixtures acting up alongside it, or a gurgle when it flushes - a drain or vent issue, not the fill mechanism.
• A new flapper that leaks again within weeks - usually a pitted flush valve seat or high water pressure, both of which need a licensed plumber's assessment.

If you are replacing flappers and fill valves more often than seems reasonable, look past the parts. Two conditions wear them out early, and both are common across the Dallas area.

The first is hard water. Mineral scale builds on the flapper, the seat and inside the fill valve, which is why North Texas toilets tend to need these parts sooner than the packaging suggests. The second is water pressure. A failed pressure-reducing valve lets static pressure climb, and high pressure is hard on every soft part in the house - fill valves, angle stops, braided supply lines, and the water heater's relief valve, which may weep onto the floor and be mistaken for a tank leak.

A licensed plumber can put a gauge on a hose bib in a couple of minutes. If the pressure is high, correcting it is the repair that stops you replacing the same small parts every year.

Call when a new flapper does not solve it, when the flush valve seat is pitted or the tank has to come off the bowl, when the angle stop behind the toilet will not shut off or will not stop dripping afterward, when there is water on the floor at the base, or when you have replaced these parts repeatedly and want the pressure checked properly.

Dallas Best Plumber is a free referral service, not a plumbing company. Tell us what the toilet is doing and we match you with a licensed, insured local plumber who repairs toilets, fill valves and fixtures - free, no-obligation quote, and no cost to use the matching service. If the running toilet turned up because your bill jumped, our leak detection service page covers the rest of what a plumber checks.