After flushing toilet water level in bowl is normal. A few minutes later the water level is lower. Why?

There are a few things that could take your level down. There could be a crack in the bowl letting the water seep out . That would be my first guess. My second guess is kind of far out but since I've had a couple of calls that lost water in the bowls, I'll throw it up for grabs. The water in your bowl is a trap/seal and connects directly to a pipe called a vent located on your roof. If that location is windy, it has been noted that the wind blowing over the vent pipe causes a suction that syphons the water out the bowl. But that's rare and you will notice the level raising and falling as it happens. I'm going to go with door #1 if only because of the time it takes for the level to go down. If it bothers you the only fix I know is to change out the bowl. The only bright spot is that it's possible that you won't need to buy a whole toilet assembly, a large plumbing shop should have bowls that will match your old tank. If you decide to do the work yourself, click on back and I'll walk you through the installation, Good luck, TOM