@Iplayfarmer:
The 3" PVC drain pipe is cheaper than 3" gray electrical conduit, perhaps because of the foam core? I used white PVC drain pipe as a catch-all that I can put in the ground in case (more like when) I do something else. The 3" is big enough for a water line and low voltage. As for the black PE pipe, if it's a run that fits in one roll of pipe, it can be a lot easier to pull wire through it because there are no joints. It's also a lot easier to install, since you just unroll it into the trench. All the low voltage in the ground (house to driveway lights posts for video cameras, LV for generator and tank, LV for driveway sensors) is in 1" 100 PSI black PE. If I were doing it again, I'd use 3/4 or 1" 160 PSI black PE because the 100 PSI stuff kinks too easily. BTW, the light posts have a 3/4 gray conduit for the light, and another for an outlet.
I bought the 1" 100 PSI black PE in 300' lengths. Bought it at a plumbing supply house since box stores didn't have long enough runs. For the 800' trench to the road, I had 3 runs- one for telco, one for low voltage, one spare in case cable or something else had to be run. It still had 2 splices, but was an easy pull, which means it could be pulled without equipment. Buried it 4' to 5' down to avoid groundhog signal fade. Water line is above it. Other PE runs are burried at 3' deep.
Hope that explains why I like them, you certainly could use gray conduit too, this was just a tad cheaper and quicker (for the PE). A win of gray conduit is you can run more electrical stuff as opposed to just low voltage. Where my outbuilding is going, I had a spare run of 3" gray conduit out of the house because I knew I wanted power out there someday. Also ran a total of 4 3" white PVC pipes. Two got used when I re-did the geothermal field, one is for the tractor outbuild and that leaves me with 1 spare.
Pete