I am building a diy block pool soon. 20 x 40 kidney shaped. I am at the point where I need to locate my skimmers and returns. I have some pool plans that only show 2 returns but I have read alot on here about plumbing and it seems like more is better. I have read about deep wall returns and other things like that. I was going to do 2 skimmers and as many returns as needed. Is the primary function of returns to circulate water or to push debris toward skimmers? Thanks for any help. I will upload a picture later for reference.