Meanwhile, back to the inspector's liability:

Apparently, there's been some recent court action on this very topic. The long and the short of it is whether a court might find the inspector to have been "grossly negligent" and so forth.

In short, you've got a shot at suing your inspector. However, I'm guessing that the fees you pay your lawyer per hour will dwarf the cost of paying a competent plumber. And besides, you were planning to do some repainting anyway, weren't you? Before you get started going down the lawsuit road, you should definitely have a close read of the contract you signed with your inspector. There's a good chance that it makes no guarantees and limits the inspector's liability.

Still, if nothing else, you can tell the inspector that he missed some obvious problems, invoice him for the repair cost, and see what happens. Don't threaten to sue (yet). Maybe the guy cares enough about his reputation to want to help you out. If a court finds that he was grossly negligent, that's pretty much the end of his business, so he might be willing to help.