I'm having trouble finding any technical information regarding the installation depth of sch40 or sdr 35 below a concrete or paver walkway. I had my yard graded last week to correct water drainage away from the home. The contractor did a great job at fixing the grade as the downpour we had this morning shedded water exacty as he described it would upon completion of the work. However I'm concerned regarding the underground downspout drains installed in relation to my plan to wrap a walkway around the home that extends from the foundation out to 4-7 feet depending on location. The 4" ads triple wall smooth pipe basically has the top of the pipe flush with grade at the very base of the downspout and follows the pitch of the yard out 20ft with an average depth of soil 3-4" above the pipe. My concern is any paver that won't have a proper base below due to the pipe being there will cause heaving, shifting or settling issues long term in the paver walk. There is only foot traffic on this pathway. Due to the overall flattness of the property pop up emitters are being used. I plan on modifying where the downspouts tie into the vertical piping by adding a tee fitting in. This will allow me to insert a plug during the summer months in the tee opeing and then swap to a downturned street 45 during winter in case the underground piping freezes and backs up. I understand the best method would be a catch basin with grate and air gap at the base of the downspout but I'm concerned it will take up too much space in the walk, add a substantial expense at $55 a piece for 5 locations, and be less adjustable in height as the final finished elevation for the paver walkway has not been established yet. I apologize as this post is a bit scattered. I have a feeling changes will need to be made and I'm already anticipating me swapping out the triple wall smooth HDPE pipe with friction fit joints for sdr35 with glued joints to prevent future root failure below these walks and the future patio off the back of the house.