No way to glue those together-- none! Mechanical fastening is the only way. Perhaps a stainless steel worm drive clamp around each of the adjoining pipes with about 4 ties under the clamps arranged equally around the pipes to hold the clamps from moving apart. A sealant such as NP-1 would keep the joint as watertight as your situation demands.

innerduct makes an epoxy glue they claim will bond HDPE to PVC. You will have to do some research to determine whether or not you think it will work.

If the line has the proper pitch there is no need to glue the joints.

"If the line has the proper pitch there is no need to glue the joints."

It keeps roots from growing into the line.

Even grass can go surprisingly deep to a ready source of moisture, let alone bushes or trees.

I must admit that all my previous experience with HDPE and polypropylene led me to believe that the only way to bond them is with heat welding. Since the proposed drain extension is not part of the DWV system, I would be inclined to try this material.

Here is a link that might be useful: Adhesive

Thanks for all the replies.

Haw anyone ever used this new stuff? I found a place that still has the old thin wall white PVC drain pipe. The new stuff looks like it might be a little more crush resistant... but having to jump through hoops to glue it is a pain in the butt. If anyone has worked with the two and can tell me if the new stuff is any better or if I should just use the old stuff that I can easily glue I would appreciate it. It will be buried about 1' below the surface and in an area that will get a lot of back yard foot traffic.

Has anyone used both? Is one more crush resistant?

Haven't tried this yet, but sounds promising.

https://youtu.be/h-9yhanz5DE