We located this piping in a brand new custom home. ABS plastic piping requires proper support straps every four feet and loose rope doesn't qualify.

How long does a trap arm have to wait until it reaches a vent? Assuming a drop of 1/4 inch per foot a 2 inch diameter arm can extend 5 feet, 3 inch diameter: 6 feet, and 4 inches and larger are limited to 10 feet except for a water closet which must have a vent within 6 feet of the toilet.