We've just bought a 2 story slab house in September and after a big snow thaw & a couple inches of rain in the same time, all the register vents filled up with water. Luckily they did not overflow and we pumped it all out. We noticed a cracked tile in one vent, the rest are all metal--as we thought they should be for duct work! Can anyone help as to how to correct the problem? (Also-the home inspection report says the house is graded properly.) Why is there clay tile in the duct work? The house is 45 years old.

45 years ago the ducts might have been nearly water tight but due to settling, cracks form. Under your severe conditions that water table rises because the water can not soak into frozen ground. Your home inspector might take a second thought at it being graded properly, it isn't under these circumstances. If you have rain gutters make sure they terminate 10-20 feet from the home. Look for dips or low spots anywhere around the perimeter of the house and level them, sloping away from the home.