All well casing will use threaded couplers for ease/speed in installation and so the casing can be pulled in the future if needed. Usually 21' lengths are used for ease of transport/storage. PVC is a good choice and it is pressure rated the same as the steel which has serious rust problems because it is mild unprotected steel pipe. IIRC both are sch 40 but I may be wrong on the schedule. Usually the steel is only 3/16" thick.
Sch 80 PVC in 21' lengths is also a good choice for the drop pipe and one manufacturer has a patented bell end with a no tread coupling feature. That's if you aren't going with the IMO better choice of coiled PE (polyethylene) tubing with only a fitting on each end. It is used in a continuous roll down to 500+' with either 160 or 200 psi rated. Galvanized is the worst choice due to corrosion and added iron to the water and then clogging due to rusting internally, which causes pressure loss and eventual replacement. That can happen in a short time depending on the water quality.
Lightening causes many pump failures each year although that doesn't mean the casing is struck.
Gary Slusser
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