I have been in the electrical flied for more than 30 years, a teacher for new electricians, and know plumbing like the back of my hand. Advice:
1. Electrical pvc. Electrical PVC is mainly used for electrical with properties that prevent the break down of the PVC in sun. As stated before by someone else the electrical PVC has special chemicals added for its intended purpose and it's highly highly not recommended to use for any other purpose other than electrical.
2. PVC drinking water. You won't find long radius 90s smaller than 1-1/2 and I disagree with some statements about using long radius 90s instead of short radius 90s. Long radius 90s are often used for mixed solids to cause a smoother flow as to not plug the line. Although if you have many 90s in your water line you will cause a large restriction in the water flow.
The following instructions you will need a form, heat restante gloves, concete, plastic wrap, a electrical PVC 90 of the final size you want, industrial hand held heater, desired PVC water line.
My advice : take a electrical 90 that you would like to use for water, place plasticwrap around it, build a form for concrete, where each end of the 90 is touching the form boards, pour the concrete and place the 90 mid way in the concete once it's hardened remove the 90, you now have a mold for a new 90 out of PVC for water. Purchase a hand held heater at Harbor Frieght for 8 or 9 dollars and heat the PVC the full lenth needed to create the 90 or longer, while the PVC is still flexible place it into the mold and press down on the top to prevent flattening of the pipe. Once cooled you have a long radius 90 you want. It's important to not let the PVC cool and reheat it a 2nd or 3rd time, each time the PVC is reheated it looses it's flexibility and it will most likely split. So once you start heating stay dedicated!
Hope this helps now and in future projects.
Paul.