Upon arrival, turned main water off at main ball valve at entry, then disconnected and removed old A.O. Smith tankless heater. Installed new mounting bracket for new Navien tankless heater then mounted new heater, reconnected to existing gas lines and water lines installing new isolation valve kit as well as reconnected to existing vent lines. Tested for leaks by turning main water and gas back on and airing out lines, all good no leaks present at this time, New tankless is working properly.