After ours was installed I stumbled across a company that makes an all in one unit called Eternal Hybrid (link below). You may want to contact them and see about getting the energy efficiency specs to go that route. I think Navien also makes an all in one system now too. I would think either company would be able to give you more accurate energy specs and better answer your question. The other thing to keep in mind is that without the loop (& pump), you are in effect wasting gallons of water waiting for the hot to kick in--think showers, sinks, etc. How much does the water wastage cost in terms of both water & sewer bills + the unnecessary waste of a resource? In addition to washing machines not pulling enough water through at a time to trigger the heater and then remain on long enough to actually get the water down the line to the machine, some dishwashers are having problems too. Here is a link that might be useful: Eternal Hybrid Hot Water Heater Site

I can't believe I still haven't fixed this... how to find the part... Looking at the docs at http://www.takagi.com/download/Service%20parts/T-KJr.pdf it seems they call that part on the diagram #419 EKN28 Flow adjustment valve and it lists at $200, but http://bostonheatingsupply.com/ekn28.aspx has it for $104 Here is a link that might be useful: T-Kjr manual PDF

Fixin, Look, when all you do is cite the negatives, don't mention any positives, and talk about the ancillary issues as if they are problems that everyone is going to face, I would call that FUD. When you talk about tankless heaters, not only is the glass half empty, but we are all going to choke when we drink from the glass, drop it, cut an artery on the glass shards and bleed out on the floor. Not all of us live in a hurricane prone area. There are real advantages on gas installations: Energy savings, continual hot water, small size and potentially lower costs to install are several of those advantages. Tax incentives and utility rebates can sweeten the deal more. That said, there are some potential drawbacks, as you have pointed out. My own experience in an older home (1920) is that it was cheaper than installing a powervent unit or a flue liner in the masonry chimney. Little gas piping need to be done (I moved the heater to be closer to the bathroom) and with the tax break, the payback of the difference between that and a conventional heater (which wasn't really an option) is about 5 years at current energy costs. That's not great, but every time the cost of gas goes up, I'm glad I made the decision. I would say that my experience isn't the same as everyone (a two story stainless steel vent through the roof could make this prohibitive, for example) but it's going to be similar for a lot of folks. My point is to get real information out there, not marketing hype, and not FUD, so that people can make good decisions. Alphonse, if you were following along with the real reasoning that gas tankless are more efficient (less wasted heat in the flue gases) you would realize that the above summation isn't correct.

I installed a tankless 6 years ago and will never install a tank again. I did it myself and will do it again if I am ever in a new house. I have a 120k Noritz unit that performs flawlessly. I just don't get it guys. Installing a tankless without recirc is like trying to start your car with a half dead battery. Really! "Your builder is right, it defeats the purpose of tankless" nonsense! I did not have recirc initially. I learned by experience you do not just replace a tank with a tankless. It is a bad result for hot water supply. Slow and inconsistent. Internal recirculation tanks might help but never having used one I have no opinion. But unless you circulate water and insulate your pipes to maintain the heat you are really missing the boat. Recirculating inside the heater means your pipes are cold and it takes longer to get to a tap because unlike a tank there is no pressure in the lines to radiate towards the taps. Why store water inside your heater when you need the heat in the pipes for faster delivery? That is just a limited solution to the issue in my opinion. How much does it cost to keep the lines hot. Depends on heat loss and vol. of water in the lines. Insulate!!! I would say my pipes take very little in cost to keep hot. Maybe $5-7 a month. I used 3/4 inch pipe for recirculation to store more water for start up and to feed 110 degree water into the heater. I do not have a timer to shut off recirculation at night so I could save a few bucks if I did that. Its a simple thing to lay out. You go to the last tap in the system and put a return to the heater from there. You need to have a cold water supply for the recirculation. A one way check valve between the recirc and the street supply prevents hot water from pumping back to the street as hot water pressure rises. A second check valve goes between the last tap and where the street supply feeds the recirc line to prevent cold water pressure from the street from back flowing through the hot water lines. Why any builder would not just put a return line back to the heater is beyond me. Its really not a lot of extra work. Especially with all the cheap Pex being used now. A small grundfos 1/25th hp pump is all that is needed in most cases. I use a Honeywell aquastat to trigger the pump. The pump engages maybe once an hour for maybe a minute to raise the water temp from 105 to 110. Heat loss? Did you insulate the pipes you say are losing heat from? You can lnstall a timer to turn off recirc in the night so you use no energy at all. You can do the same during the day when you are not at home. For some families you could have a daily timer that changes recirc to match your schedule. The hot water works with the recirc off, it just does not work properly as iz well known. Tankless is a superior technology. I did not think the endless supply would matter to me, its noticeably better. A tank cools as soon as you start using water out of the tank and cold water replaces it. The temp drops and drops the longer it flows. A tankless heats water on demand and it is maintained at the same temp. Its really is an advantage. But, as has been stated here by users, un managed hot water supply sucks and who cares if it costs a little bit of money to heat and pressurize your pipes so hot water is instant. Its way less expense than keeping 40 gallons of water hot in a tank. I would never heed the advice by someone on this thread that you don't need recirc. Have your builder install a true full house recirculation system. Don't pay attention to this "you don't need it stuff." If the builder balks or talks down to the idea get someone who knows what they are doing to come install it and over ride their obstinate attitude. Just do not listen to the talk of having a better system is not needed. You are going to great expense to have the best hot water supply you can have. Don't let someone with out your best interests in mind wreck your enjoyment of a great tankless system. Recirc all the way!!! Gee people, why would anyone not do this in new construction when its way easier to do.