Return Header Sizing Help

[HockeyRooster]

I am plumbing my new to me 90 gallon tank with a 33 gallon sump. As of now I don’t have any reactors to add to the system (i have a reactor but not really sure what to put in it at this time).
I think eventually I’ll add stuff to the return side of this system so I think I should create a header now. That brings me to a question about plumbing a header. I am being mindful of not reducing flow too much and am using 2x 45 degree fittings. when I look at pics of headers they all seem to have 90 degree fittings. So what gives? why is it recommended to not use 90s when it seems everyone uses them on the header?
I have a 1000gph pump with a 1” exit and my return plumbing will be 1”.
please school me on my header plumbing. Thanks!

 

[Snoopy 67]

If you have the room there is nothing wrong with 2- 45's. On a drain you are only working with minimum head pressure so depending on the reactor (GFO) it might not work .

 

[HockeyRooster]

Thanks. Going to use a combo. 2x45 when I can and 90 when I can’t