In my area I like to figure an exposed outside run of PVC is exposed to a temperature change of 100F.
Given that temp change I need an expansion fitting where 6' or more of PVC is installed between fixed points.
I get a lot of grief for using 100 F. People ask how often do you get a 100 F day or how often do you get a -10 F day?
IMO how often is not relevant, what is relevant is it does happen. When I see exposed PVC runs that people have not installed enough expansion fittings in I either see the fittings pulled out or the PVC looking like an ocean wave.
I also see people forget that PVC support spacing is not the same as EMT.
6" PVC requires a support every 8'
3 1/2" to 5" PVC requires a support every 7'
2 1/2" to 3" PVC requires a support every 6'
1 1/4" to 2" PVC requires a support every 5'
1/2" to 1" PVC requires a support every 3'
