you say that the line to the tank is clear?the problem with useing chemicals, is they can burn away fittings joints if there made is plastic,they can be very strong, i would use rods back as far as i could go back up the line from the tank , to make sure its clear. not sure it the toilet is new or old , ,if it was new i would take it away from the wall , and then you will see whats blocking it, but i dont know the set up . tiles around it ect, there is also dino rod, company, they will blast it, might work out faster, good luck
g
February 2011