Welding a lot of PVC joints...

[Poconos]

Another hint...when you do the dry fitting you probably won't get all the joints to seat all the way. Sched-40 fittings seat 1.25". Then when you goop they seat all the way and measurements are off.
Al

[JohnT]

Another hint...when you do the dry fitting you probably won't get all the joints to seat all the way. Sched-40 fittings seat 1.25". Then when you goop they seat all the way and measurements are off.
Al

I'll quote that just to emphasize how important it is.

It's also handy to write notes and little arrows in pencil on the pipe about which end goes where and what direction it goes so you don't point an elbow the wrong direction.

I've also found that dry fitting can mislead you into skipping a joint when it comes time to glue. Not a good feeling when you see that an unmoveable joint in the middle is leaking because you forgot to glue it. Purple primer is your friend for anything underground, but it looks pretty bad above ground unless you'll be painting the pipe.

Make sure you have some extra fittings on hand. Nothing more frustrating than messing up a section and then being short a fitting to finish.

[catnip]

I used unions on the pump, filter and SWCG. The Jandy, Pentair, Compool valves can be repaired in place, so I think unions are overkill there. You might also consider a union for any place where you can't physically make a good glued slip joint, e.g. tight spot where you have no room or flex in the pipe to fit the slip joint together.