A toilet that runs continuously, or one that briefly refills on its own every few minutes even when nobody's used it, is one of the most common calls we get, and it's also one of the most consistently misunderstood. People assume it's a sign of a bigger problem. In the large majority of cases, it's actually one of two small, inexpensive parts that have simply worn out.
The Flapper Is The Usual Suspect
Inside the tank, a rubber flapper seals the opening at the bottom, holding water in the tank until you flush. Over time, rubber flappers degrade, warp slightly, or develop mineral buildup along the sealing edge, and any of those problems can prevent a clean seal. Even a small gap lets water slowly leak from the tank into the bowl, which triggers the fill valve to keep topping off the tank, and that's the cycle you're hearing as constant or intermittent running.
This is genuinely a five-minute repair in most cases. The flapper lifts out, a new one of the correct size and style goes in, and the running typically stops immediately. It's one of the most cost-effective repairs in residential plumbing precisely because the part itself is inexpensive and the labor is minimal.
The Fill Valve Is The Other Common Cause
If the flapper is sealing properly but the toilet still runs, the fill valve itself may not be shutting off completely once the tank reaches the correct water level. This can happen when the valve's internal mechanism wears out, or when the float that signals the valve to stop has drifted out of adjustment. A running fill valve usually sounds different from a flapper leak, more of a persistent hiss or trickle rather than the cycling pattern a flapper leak produces.
Signs Pointing To Each Cause
Water Trickles Into The Bowl Periodically
This intermittent cycling pattern usually points to a flapper not sealing fully.
Constant Hissing Or Running Sound
A continuous sound, rather than a cycling one, often points to the fill valve not shutting off.
Visible Wear Or Mineral Buildup On The Flapper
Lifting the tank lid and inspecting the flapper directly often shows the problem clearly.
Water Level Above The Overflow Tube
If the tank water sits right at or above the overflow tube's opening, the fill valve isn't shutting off at the correct level.
Why It's Worth Fixing Right Away
A running toilet can waste a genuinely significant amount of water over the course of a month, often without the household immediately connecting the sound to the water bill. Because the repair itself is usually so inexpensive, there's rarely a good reason to let it run for weeks while you decide whether it's worth addressing. Our toilet repair service handles both flapper and fill valve issues directly, following the fixture standards set by the Uniform Plumbing Code (UPC) that Washington has adopted statewide, and most visits resolve the problem in a single trip without needing a full toilet replacement.
If you're dealing with a running toilet alongside other fixture issues in the same bathroom, a dripping faucet or a slow sink drain, it's often worth having both looked at in the same visit. Our faucet and sink repair service covers the same kind of small, worn-part issues that make a faucet drip, and it's common for a bathroom that's due for one small fixture repair to be due for another at the same time.
When It's Actually Something Bigger
Occasionally a running toilet is a symptom of something more involved, a cracked overflow tube, a warped flush valve seat, or a tank that's simply old enough that multiple internal components need replacing at once. If a flapper and fill valve replacement doesn't resolve the issue, or if the toilet is old enough that parts have become hard to source, a full replacement genuinely becomes the more sensible option. We'll tell you honestly when that's the case rather than continuing to replace individual parts on an aging unit.
A Quick Way To Confirm A Leak Yourself
Before calling anyone, there's a simple test that confirms whether your toilet actually has a leak: add a few drops of food coloring to the tank water, wait about ten minutes without flushing, and check the bowl. If color appears in the bowl without flushing, water is leaking past the flapper seal, confirming that's the source rather than the fill valve. This costs nothing, takes a few minutes, and gives you a clear answer before you decide whether to tackle the repair yourself or have it looked at professionally.