Their own version of a "leak minder".
Along with a leaking flapper valve.

Travis Jordan wrote in message
.. .
Butch Hinton wrote:
HI all,

This morning when my wife went to flush the ole commode, there was
very little water in the tank. I checked to see if the faucet to the
tank was closed and it was open. I closed the faucet and reopened and
the tank filled. Now every time we flush, the tank only fill to about
an inch on bottom of tank. I closed the faucet and reopen it and the
tank fills.

Any idea??

TIA
Butch

Stuck fill valve.