As the Lake Forest, Ill., kitchen rehab nears completion, the countertops are installed, as is the cast-iron farm sink and a faucet system that features a retractable sprayer head and an undercounter water-filtration unit. Also: host Steve Thomas visits a stone-fabrication shop to see where the Italian-sandstone countertops are made. And in “Ask This Old House”: plumbing-heating expert Richard Trethewey installs a leak sensor and a water-heater shut-off valve to prevent basement flooding, and contractor Tom Silva repairs an exterior door jamb.