The pipe from the submersible is a typical plumbing pipe like pvc. The submersible pushes water up. When it reaches the pitless, it does a right-angle bend and goes out through the side of the casing. Then runs underground to your house. The pitless is, essentially, just a joint that redirects the water ninety degrees and fastens securely to the side of the casing.
The Simple Pump is a completely separate system, alongside your submersible. We can't, somehow, use the submersible pipe because our pipe is not JUST a hollow pipe - it contains a series of rods that connect the lever arm at the top to the pump piston and a cylinder at the bottom.
There needs to be some way to get the water in the Simple Pump drop pipe out through the side of the casing. That way is our specially engineered pitless adaptor which allows pumping from the top while diverting the water sideways.
Once the pipe is taken sideways outside the well casing, the pipe can then easily be joined up with a T junction and with the pipe coming from the submersible, so one pipe continues underground to your house. Each branch of the T has a one-way check valve, so the operating pump doesn't pump water down the other branch to the other pump.