they told me the biggest i could go is a 14ft. trailer with a single axle and what i was wondering is where should the axle be placed to balance out the trailerits just to haul around 3 atvs and maybe some other light duties
Axle placement must be slightly back of dead center, around 12 inches
You'll have to cut out the elbow and replace with new PVC. Give yourself plenty of room to add a union (pipe to pipe) then another elbow (pipe-elbow-pipe) then another union, (pipe to pipe) Make sure to clean the PVC with the purple stuff and use the cement as directed.
If the axle is to be mounted on leaf springs, put the front spring hanger 6 behind the center of the trailer. If no springs will be used, mount the axle 12- 18 behind the center of the trailer. You always want some tongue weight on the trailer even when empty.