Over eager toilet that flushes twice...why?

[AHI in AR]

I came across a toilet in a home today which would flush twice with one flip of the handle. The water would swirl and drain, looking normal, then refill again quickly and drain again. Two other toilets of similar design in the home didn't do this. Unfortunately, the sellers came home with a sick baby and I wasn't able to pull the cover off the tank and run it through a few cycles to try to figure out what was happening. It was a conventional toilet, not anything exotic.

Anyone know what's going on?

[Marc]

Partial clog in the drain, the float has lost some buoyancy or the water level in the tank was too low to do the job on the first flush.

Marc

[AHI in AR]

I dunno. By my admittedly unscientific approach of simply watching all three toilets flush I'd have to say that the amount of water that went out with the first flush matched that of the other 2 toilets in the home.

[Stephen Lagueux]

perhaps the succion of the water going down from the first flush sucks the second fill down with it. Possibly caused by undersized drain and or bad ventilation....having one of those would come pretty handy sometimes.

[kurt]

Kohler Wellington's did that a lot if someone reset the foam thingie on the flapper chain.

[Les]

Kevin, are you saying the water left the bowl (completely) twice or are you saying the tank released water twice?

Not an uncommon thing with mis-matched tank/stool.

[AHI in AR]

Les--

The water swirled around and drained as is normal. But instead of simply filling back up it filled up quickly and then flushed again just as soon as it was through filling. The bowl then refilled as it should with no more flushing. All 3 toilets in the home were identical. This was the only one doing this so it wasn't a mismatched bowl/tank issue.

[4000sposse]

Sounds like it is draining too slow once the water flushes out of the bowl (partial clog like Marc said), and the bowl is filling up fast enough for the siphon effect to continue and flush the bowl again.