Here's what you need to know to install a gas water heater. http://www.lowes.com/projects/repair-and-maintain/install-a-gas-water-heater/project. Difficulty Level: Advanced Installing a gas water heater involves potentially dangerous fumes. A properly functioning flue is necessary to remove harmful gases. If you are not 100% confident installing a gas water heater, Lowe's recommends that you hire a professional. Call 1-877-GO-LOWES…