Tapping into existing three inch pvc landscape drain pipe

[Dylan]

Have a small landscaped area with minimal sun exposure that gets damp and seeps into garage through stem wall. Drainage/ foundation company took a look and suggested adding a drain and tapping into existing three inch landscape drain pipe. Too small of a project for them and their minimum fee and running into same problem with out landscape companies so I'm hoping to handle it myself.

Planning to run a NDS Channel drain and tap into existing three inch landscape drain pipe. Current set up is gutter downspout from upstairs patio dropping into the three in pvc pipe and exiting into asphalt drive. Looking for suggesions on how to connect new pcv to exisiting and whether putting in a T connector or saddle would work better. The saddle joint is hard to find around here. Have the channel drain with a two inch to three inch connector, three inch solid wall pvc, and some elbows and a T connector with plan to cut out existing and put channel drain and downspout into T connector and reconnect to pipe running to asphalt drive. PVC pipe I got is sold wall white pvc but exisiting has black coated lining inside white pvc pipe. Do I need to get a different kind of pvc pipe or is it ok to run the white interior pipe draining into the black interior pipe?

Thanks.