I have read a lot of posts where people have concerns about big tanks and the structural integrity of their houses. I personally have a 300 (96Lx24Wx30H) set up in the second floor of a 65 year old building. I tend to think it would have to be a pretty rickety house to have a problem. A standard (50 gallon) water heater weighs about 500 lbs over an area of about 3 square feet = 166 lbs/square foot. My 300 weighs about 2800 lbs over an area of 16 square feet = 175 lbs/square foot. Not that different... All that said, has anyone ever had a tank crash through a floor?