SylvanLMP
You must without ANY doubt remove the old trap.
The reason you do not want double trapping is Air bound drainage systems cause stoppages and a heck of a breeding place for bacteria as you no longer have the proper scouring action.
You cannot snake a line through TWO P traps.
Your slowing the drainage line with a lot of restriction by using one trap TWO forget about it.
Have a GREAT ONE
