You’re standing in the bathroom, you haven’t used the toilet, but it starts running for a second, and then stops. What is going on? This problem is calleda phantom flush. Your toilet is wasting water and driving up your utility bill. There are simple fixes to this problem, but first, you need to understand what has gone wrong. Here’s why your toilet randomly runs for a few seconds.

Why a Toilet Runs

A toilet runs when you flush it in order to refill the bowl and tank. If your toilet is running when you have not pulled the handle, then something is triggering the flush mechanism. There are several parts to the mechanism you need to understand:

  • Chain: When you pull the handle, it pulls on a chain inside the toilet tank.
  • Flapper: The chain is attached to a flapper, which, when it lifts up, allows new water into the toilet bowl.
  • Fill valve: When the water in the tank gets low, a floater or another mechanism triggers the fill valve. This valve will allow the tank to fill from the waterline. When the tank is full, the valve should close.

Why Your Toilet Runs Randomly For a Few Seconds

When your toilet runs randomly, something has gone wrong with the flushing mechanism. Most commonly, something is preventing the flapper from closing completely. Therefore, it is always letting a small amount of water out of the bowl. Then, once the toilet tank is empty, the fill valve is triggered, and it refills the tank. That’s what you hear when your toilet runs for a few seconds—the tank refilling.

So, the question is, what is keeping the flapper from fully closing? Sometimes it’s the chain, it could be too short, or it could be getting caught on something. Or, the handle itself could be stuck too high, preventing the chain from fully lowering. Calcium and other mineral build-ups in the tank could prevent the flapper from making a proper seal. Or, the flapper could be broken, chipped, or stuck.

That’s just the root causes of one potential toilet problem. If the issue isn’t with the flapper, then a whole host of other problems might be causing your toilet to run. The floater or the fill valve may not be working properly, for one reason or another.

In the end, you’ll need a plumber to find out the reason your toilet is running randomly for a few seconds, and to fix it.

Why Fix a Running Toilet?

A toilet with a phantom flush may not seem like a big deal. Afterall, you just hear it flush once or twice per day—so what’s the harm? First, the toilet is likely flushing much more often per day; you just aren’t nearby to hear it. These extra flushes are wasting water. In fact, they could even double your water bill if the phantom flush is happening often enough, or if your toilet has a very large tank. To keep your water costs low, it is best to get this problem fixed right away.