Bought a replacement Rheem tankless water heater and mounted it on an outside wall in same position as old heater. Old heater vent was vertical through the ceiling, non stainless and new style required S/S venting. Decided to change to a horizontal vent setup. Bought the horizontal vent kit from Rheem that was designed to work with the heater model. Went to install the vent kit and found that in order for the elbow to fit through the wall, the heater needed to be mounted AT LEAST 5.5 in AWAY FROM THE WALL. Nowhere in the heater instructions OR the vent kit instructions do they indicate a minimum for clearance to the wall in a horizontal vent situation. In fact, the brackets that come with the heater only allow adjustment for about 2" clearance to the wall.

I'm going to have to rig something up to make it work. The whole purpose of getting the kit made for the heater was so that I wouldn't have to figure out adapter sizes, pipe lengths, etc. Most of the instructions were boiler-plate stuff warning about dangers of CO poisoning. Stuff that the lawyers made them add, I'm sure. Not much about the actual installation and NOTHING about dimensions.

Sorry for the rant, but this isn't the first time I've bought something that didn't fit its intended use and I've had to modify it.