"Bob M." wrote:

What causes a toilet to lose some of it's water in the bowl? After flushing
it, it fills up just fine. When it stops filling, within 30 seconds the
water level in the bowl drops a bit (maybe 3/4") and stays there forever.
No leaks, two-piece toilet.

Check out:

http://www.1800anytyme.com/blog/15-e...t-tune-ups/36/

Excerpt:

"7. Toilet Bowl Water Level Drops

After you walk away from the toilet and the tank has filled, does the
water level mysteriously drop? If so, two things can be wrong. The
toilet may be partially clogged. The clog can actually cause a siphon
and pull water from the bowl. The other possibility is more severe.
There can actually be a crack or small defect in the colon of the
toilet. This is the channel that water passes through to get to the
drain pipe. A colon crack or defect means it is time for a new toilet."