Why does my toilet intermittently run continually?

Question

I've pretty much fixed up my bathroom since moving in. The last bit of annoyance now is this:

Not every time, but every 10 or so flushes, my toilet will run continually. It'll sound like it's water is filling up for about two minutes, then stop for five minutes, then sound like it's filling up again... on repeat. To stop it, I have to go back in and jiggle the handle.

One time I took the lid off the top of the toilet and it looked like it was slowly losing water from the top (or whatever it's called).

Any idea on how to fix this?

Answer 1

I would first try to replace the flapper, it may be old and worn and not creating a proper seal. If that does not work try replacing the ballcock (float valve), as these too can become old and worn and not function properly.

Answer 2

If the water is leaking from the top, then you probably have the shut off level too high (the level set where the float eventually rises and shuts off the flow of water into the toilet tank). Then the water can continue to "leak" out and eventually it might trigger the tank to start filling again (on windy days you might see it happen more as the wind blows and moves the water in the toilet and tank). You should be able to adjust the arm that attaches to the float so that the shut off happens and the level of water is below the top of the "tube" (not sure what that is called).

Answer 3

I have also found that buildup of minerals or iron by-product can foul up the mechanism that lets the float detect the water level. I have a lot of crud in my water because I'm on a well. Harmless, but smelly. So I have to take apart the toilet mechanism about every month or two and scrub it all out.