Can you install a water heater I received as a gift from a cousin who bought it from an internet clearance site? No. In some cases, like installing certain whole house water filtration system brands, after consulting with you we will direct you to purchase the unit/modules yourself and will gladly install the system for you. On rare occasions when we accept to do an installation with a customer supplied equipment we will only guarantee the vent, gas and water lines modifications for the usual 60 day period and we will not provide any free of charge equipment service. Exception for veterans and first responders in regards of discounts on purchases only from Home Depot and Lowes- please call us for consultation and assessment before you purchase a water softener, water heater or a tankless water heater. Buying the wrong unit at a slight discount may cost you much more because of a more complicated installation, inadequate volume supply and lower energy efficiency than the right equipment for just a few dollars more.