The sequence is immaterial. The first one in line will be the first to go bad so you would want to decide whether to balance the lives by putting the new one first and expect that it and the older ones might fail at about the same time. Or put it last and let it outlive the older ones.: I have a four apartment house. All the apartments share two gas hot water heaters : that are configured in series (1st – 50gal 65000BTU/2nd – 40gal 35000BTU). : I currently have the 50 gal set to moderate and the 40 gal set to hot. : Low Flow Shower Heads have helped, but I probably need to add another hot water : heater.: Should I add a third heater or is there some sort of instant hot water system? : I could probably get another 40 or 50 gallon heater and fit it between the other two. : Should the higher btu heater be placed before or after the lower btu heater to : ensure minimum recovery time?
