thats what i was thinkin. what do you mean by centerlines to get straight pipe length? where should i get those 90's?Well, you could put the ports towards the bottom of the box, use 2-90's and turn the pipes towards either side, then 2 more 90's and turn the inside flares up. Measure the centerlines of the 90's, subtract to get the straight pipe length.
^^^ Here.I was mistaken. Just checked the PSP site, the flares account for 5", so the straight pipe would need to be 3".
You can get PVC 90's from HD or Lowe's or any hardware store that carries plumbing supplies. You'd be better with the sewer pipe fittings as schedule 40 water line fittings have a bigger I.D. They may not be a tight fit, so you may need to wrap the pipe to increase the O.D. for a snug fitment.