Can 4" shc 40 electrical pvc be used for water well casing? I have an excess of it. Seems like the only difference between it and regular sch 40 pvc is just color. I need to drill a new water well on my property for filling my pond. Any thoughts on this.

I don't see why not. Schedule 40 Electrical PVC is rated for water vas well.
Here's what I pulled up from a supplier

Quote:

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Electrical PVC Pipes
Electrical pipes, conduit, fittings coated with polyvinyl chloride, used for cold water. Electrical PVC pipes are used for applications such as water services, and for irrigation.

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Good luck, Tom