OK I've read a lot of forums on this subject and have tried all the suggestions.
Here's my problem:
I have 2 bathrooms, one toilet works fine. Flushes great, bowl has correct level. This toilet is closest to the septic tank.
My other toilet is farthest from the septic tank and is the first drain along with the bathtub on the system. This toilet has always had a low water level in the bowl, since the first day we moved in. new house. I've checked the vent, it's not clogged. Put vacuum cleaner hose down vent and cut in on so it would blow and blew water out of the toilet and bathtub. I replaced the toilet with a brand new one. Does the same thing. I flush and the bowl fills up and then drains out leaving only a small amount of water in it. The vent seems to be OK, new toilet rules out crack in the bowl (unless you think I got two cracked bowls?) I've checked the trap under the house to make sure it was tight and not creating a vacuum. The only thing I have not done is check the system for a partial clog. The reason I have not done this is because the bathtub and sink in this bath room drain fine. I'm at a loss. Any help would be appreciated. Thanks.
Greg

It is possible that the partial clog is right where the WC meets the drain... pull the WC up and snake the line just to be safe while the WC is out run a snake through it as well

I kmow what I'd do. I'd pull that new toilet, put the bowl up on saw horses,fill that sucker with water and see just where the water went. That would be the first place I would start. One thing I've learned after over 50 years out in the field is Never take anything for granted. Check the new bowl out and get back to me. Also when you had the old toilet out was there a lot of air flow action from the open closet bend? Let's hear back from you. Regards, tom