i need to replace an old toilet in a little 1 level house. i'm doing almost all the repair and upgrades to this house by my self...with a book in one hand and a tool in the other. the house is about 140 miles from where i live, so i'm not there more than 10 times a year at this point. the existing toilet was placed in the 1960's, not sure when, but the exit hole is directed to the front of the toilet and not the rear as i see in the newer toilets. never really paid much attention to toilet holes before. the toilet plugs frequently, i've used drain cleaner, drain opener, root killer, all without any long term success. the water from the plugged toilet will back up into the bathtub. i've decided the drain needs rotorooting and since i will probably have to replace the toilet anyway, i may as well do that while the plumber is there. the problem is...i dont know if the existing toilet is a 10" or 12" measurement. is there any rule of thumb about these old toilets? it does sit right up against the wall.