I think this may be helpful for those who are considering replacing an existing tank-type heater, The heater arrived exactly when it was supposed to; the thing that got me was how small it was, even though I'd checked the dimensions before purchase. We have very old and internally rusted 1/2" galvanized pipes, but are planning to finish a copper replacement project soon. Since I didn't want to do things twice, I used copper for the neccesary repiping; as I didn't want to clog the heater, I elected to install a water filter on the inlet side which lowered the water pressure even more, near to the bottom end of acceptable. A pressure safety valve of 150 PSI or less must be installed on the outlet side and is not included; I pulled the one from the old heater, which worked fine after I built a T extension to accomodate it. The heater should be mounted to a stud and as close as posible to the old vent system; you may be able to grandfather the old system if it's in good shape, the heater is located in an unheated area with good ventillation. and the vent pipe has several inches of clearance (particularly on the top) Another important thing is the temperature setting; I found with the gas in 1/2" pipes that the max temperature was just under 115` F. The important thing to remember is the hot water flow is endless, so it is not neccesary to mix with colder water to extend the usable time; consequently I set mine to 114`. This worked perfectly and I could shower as long as I liked, while allowing a slight mix with cold water for a comfortable starting temperature. You'll probably need an extension cord for the electronics; although the length is given as 10', it is actually 6'. I think this heater is a HUGE bargain. It cost less than replacing the old one with the same model, has a longer warranty and should save a lot of money over it's lifespan, Although I had initial concerns over whether it would work for my situation, I found it did with a little tweeking and was very pleased with almost everything about it.