Ask This Old House heating and plumbing expert Richard Trethewey helps a homeowner install a natural gas line to fire up his backyard barbecue grill. SUBSCRIBE to This Old House: http://bit.ly/SubscribeThisOldHouse Time: 3-4 hours Cost: $2500 Skill Level: Professional Tools: Adjustable wrench Press tool Drill/driver Emery cloth Masonry bit Shopping List: Grill with natural gas…