What are these 3 thin lines draining into my sump well?
Suggestions for investigation:

(1) Temporarily attach it to a piece of transparent tubing held vertically above the sump, to see how high the water rises. This will give you a clue to the location of the source.

(2) Force high pressure air into it and walk around listening for a hissing noise.

(3) Stop it up and see what floods or overflows.  Be prepared with mops, bucket, shop-vac, etc.

(4) Inject a harmless dye or other tracer under pressure and see what turns colors.  Green is best for deniability if it turns out the source is not on your property.