I have installed a rinnai direct vent unit. A partner helped me run one inch black pipe from the meter through the crawlspace into the closet. Gas volume is critical, too small a supply will cause problems. After removing the small electric tank that came with the house and the wiring to it, I drilled a hole through the wall for the intake/exhaust pipe. The heater itself hangs on the wall and as long as you can 90 degree elbow exhaust right above it, there's no need to worry about condensate, it will drain outside. Slight pitch downwards for this to happen. I haven't put a an outlet in there yet, just using an extension cord for now. My cost was slightly above 1000 dollars to install it and I work in the HVAC trade. I love this unit! Major drawback: teenagers realize they have unlimited hot water, so you have to kick them out of the shower! Most people call these units instantaneous which is incorrect, correct term is on demand. You still have to wait a few seconds for hot water down in the back bathroom.