The vent system that is on that pool heater is for use in an enclosure and is supposed to have a top on it also, not just end with the draft diverter like it is now. They make a different top for that heater when installed outside. The code says 4 feet from any opening into a structure which inscludes operable windows. The next issue would be the tape, which you would not need if the unit had the right top on it.