I would make the calculation of amortizing the cost of the tankless vs the standard HWH. The 2 capital investments+operating cost 1-Tankless + piping and meter installation+maintenace 2- 80 gal HWH + operating cost maintenance plus cost of loss of heat from tank If you could supply the numbers for the capital costs maybe you could get additional help here.

Jerry, The reason for statements about tankless and manufactured homes/mobile homes and it's restrictions is because of several codes require sealed and special venting for such applications. If you are in a warmer climate, many are installed outdoors, or in outside utility closets as you speak, as long as proper venting, combustion air and clearances are followed. The big three water heaters today and in sales order is: Rinnai, Noritz, Takagi. They are there and on top for a reason-quality After that the Paloma's, under many names, Bosch, and a few others are fighting over the bottom. One to watch though is the Navien which is gaining ground fast with the highest efficiency out (98%), PVC venting and stainless steel heat exchangers versus all others have copper (susceptible to liming, calcification and erosion). bstarz, Many studies place tankless payback above a tank replacement at about 7 years. Of course if you pulled a new tank that had a 7-12 year life expectancy, then your ROI could be close to 15 years. Dan "Palomas in restaurants near me that have been running for several decades without any problems" Really 30 years or more? Life expectancy of a copper tankless heat exchanger is 10 years, commercial application used 3 hours a day. Use it for 6 hours and it is 5 years. With Paloma only starting distribution in the US since '88, I doubt they have been in a restaurant for several decades (30 years). To all, if your considering a tankless, don't go cheap, if payback is a consideration, don't have one installed till you need a heater, if energy savings is desired, unless you control the never-ending hot water supply (teenagers in showers), you wont have any, and last if you can afford, want endless hot water because you run out, go for it!

okay, So, the water comes out of the hot water faucet, but it's not hot. Yet you say that the water heater is hot. Check again to see that you have the cold water line hooked to the cold water inlet on the heater. That side hooks up to a dip tube that goes to near the bottom of the tank. The idea is that the cold water is introduced on the bottom and the hot water rises to the top where the outlet is. The Hot and Cold are marked on the top of the tank. Just confirm that it's right. A less likely problem is that the dip tube is missing or broken so the cold water is introduced at the top and then goes directly out the hot side. I'm taking you at your word that the heater is getting hot (meaning that the elements are working and the power is connected properly).

You can certainly do a hybrid or combination system. Doing your proposed L/R lay-out, is the only way to go in my opinion, I would still suggest a pipe tying the two sides together. I would put and accessible ball valve in that cross connection pipe so, if for any reason one system went down you could open the valve to have one side support the other, at least temporarily. Do you have a basement under this home or only a crawl space? If you need hot water quickly and not shower volumes in the downstairs rt lav, perhaps a small undercounter electric would do the trick. I hate to suggest that, but you are dealing with geography here. Time, distance & flow rate . The Master Bath will be best serviced by tankless. Your hi flow shower head needs to have a specific flow rate attached to it. A standard shower head will provide 2.5 gpm. In my new shower that means 2.1gpm of 120f water mixing with .4gpm of cold to arrive at my nice comfortable shower temp. I have also seen 20 gpm shower heads. Put a number on the flow of the single shower head please. What is the volume of the tub. What faucet set are you putting on it and is the tub valve going to be a 1/2" or 3/4" connection. With 1/2" pipe you will not get much over 5 gpm. With 3/4" you can get 10-12 gpm. Some tub faucets, the waterfall type, require 3/4". Otherwise the visual effect is not as good. Get the tub volume and compare the flows to the time you are willing to wait for the tub to fill. Yes, you can put tankless in the attic, but understand that you need a pan below them to prevent water damage from any possible future leakage. That is just good sense. Tankless water heaters are compact. As a result people tend to install them in really small spaces. Please keep in mind that this is a mechanical system and must be accessible for inspection and service. I long ago coined the term, "Just because it fits, doesn't mean that is where it goes." You would not believe the places people have installed these. It is a good idea for you to have the "service space" discussion with all of your subs. A lot of duct work gets destroyed by the technician the first time he has to service the heat pump, furnace or air handler. Build all your system to perform well, but make sure everything is positioned for accessiibility. These types of agreements tend to be forgotten when the equipment arrives on the job and the contractor wants to "get it done". So the question to your General and each of the subs is, "How are you going to build and position the equipment so it can be easily serviced". That is a good discussion to have with your architect too. Make your expectations clear and let them know you will be following up to monitor this "agreement". Sorry to get off topic there, but you have what, as I look at the floorplan is going to be a really lovely home. I just want to make sure the cardiovascular systems work well for you too. Another thing, the gas line will have to be sufficiently sized not only for what you are planning for the initial job, but you want capacity for future expansion. I have seen so many places that get undersized gas lines and the owner is blocked from any possible future expansion. This is a big project and even with great care, things pop up.