I’m building a 29 gal reef tank with 20 gal sump. The sump is directly below under the stand. I’m using a fiji overflow box so I will have 2 pipes going down then making a 45° turn into stand and then another 45° turn down into the sump. I will be using a gate valve somewhere on one of the overflows, the one that’s not emergency. For the return I am using black vinyl tubing until it gets out of the sump and then using a fitting to bring it back to hard pvc (using sch 40 furniture grade black pvc) and then a 45° turn to the tank where it will go through the tank and into a nozzle for return. So my question is- Where would I need unions in this set up? I know it’s a dumb questions I’ve just never used unions before and don’t know where they’d best be placed. Thank you