Water – How to do about water filling the excavation for a house’s foundation

I would second the comments recommending a second opinion. A sump is in the basement to allow water to be drained away if it accumulates around the footings. If there's no water there it quite probably means that your water table is low enough that there's not seepage. It also would indicate that you have decent drainage around the house and rain water is running away and not down along the foundation walls.

Even if there is a blockage in your sump I would expect there to be some water in the bottom if you currently have a water problem. Blockages often involve crushed weeping tile or other drainage pipes. However, it would not usually be a complete blockage and if you have a have water on the outside trying to get in at least some of it should be seeping into your sump even through damaged draining lines.

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.