How much pressure can Loc-line take?

[Gools]

I have a GenX 18000, 4750 gph. and I want to know if it will be ok to come out of 3/4 locline? I have 3 "T''s only 2 will be used for water flow right now to other tanks, then a 90 at the top to a "Y" to give me 2 returns to the tank. which will be the locline, which also has a "Y" on both splitting them. Pipe from the pump is 1.5 " going down to 1" Not sure if 3/4" will cause to much back pressure? I don't want to waste flow if it will.