We had the flooded bedroom scenario when the toilet did not shut off due to low water pressure from the campground we were staying in at the time....Thetford said their toilets are designed for 40 psi and up and anything less the valve may not close all the way....
I installed a brass ball valve at the toilet and we always turn off the water regardless if we are home or not....
http://s962.photobucket.com/user/myb...?sort=2&page=1
All total it took about 20 minutes to do the job and cost about $20.