I need a new hot water system. Suggestions please.

[starfish11040]

I have a building of ten small apartments, mostly studios. Twelve people, all adults. Apparently there is a lack of hot water on some weekday mornings after 7:30 am. I'm sure it's because it's the morning rush and the lack of hot water is due to a temporarily insufficient volume of hot water because too many people are showering at about the same time.
It's a gas-powered two-tank system. Each tank is 42 gallons. They're eighteen years old so due to be replaced anyway. My understanding is that the new system should resolve the supply problem by having higher storage capacity and, I think, a better recovery time.

I will be getting two or three plumbers to come in and give me an analysis, recommendation for replacement, and a cost estimate.

My question here is what specifics should I be asking about? btu's? flue size? FHR? EF? etc. I really don't know much about this.

thanks

 

[rfdevere]

Tank size and recovery time are all you should focus on, if the tanks are together i recommend one massive tank opposed to 2 small tanks. If the tanks are at different places in the building then obviously 2 small tanks will be the way forward or one with a circulator pump and LOTS OF LAGGING

As for flue size etc don't even worry about it, its not related to the hot water demand.