Toilet bowl losing water

[Howie A B]

Hi: I have two adjacent bathrooms. One of the toilets is losing water in the bowl maybe an inch per week. From what I read, it could be venting or a crack in the bowl even though there is no visible water leaking. I flushed the properly working toilet 10 times to see if it was pulling water from the bowl of the problem toilet, no change in level at all. No gurgling, all drains and toilets work fine. So do i conclude that the issue is an internal crack in the problem toilet? Thanks for your help.

 

[Twowaxhack]

Could be dental floss or anything wicking water down the drain . Or it could be a crack but the water should show up.

you could try running a closet auger through the toilet and see if the problem stops