2nd story:
2 kids bedrooms on left
Master on right
Upstairs laundry

(downstairs plan shown on prior post has frequently used guest room on left, kitchen area on left, then 1 smaller bathroom that won't get much shower use but needs hot water in faucet quickly on the right of the plan on the prior post).

This post was edited by kath0000 on Thu, Oct 17, 13 at 0:39

Please, ahead of time, pardon my lack of brevity, but here goes. First of all my disclaimer. I am a major fan of tankless in general and Rinnai in particular. I represented them in a six state area for over 20 years. I continue to consult with them. I just installed my new one in our re-model, which is finally...finally beginning to wind down.

You do not say where you are located. As I see it, you have a few options. You could, as you say put in a couple large tanks and pump them, but that is incredibly inefficient. You obviously have the resources to do so, but you will spend more in "heat loss" on the piping than you actually spend on your hot water. I would add a DHW solar system to drive this, but unfortunately solar thermal hardly ever returns the cost. In your system however it may do very well due to the requirements and the building lay-out.

A second option would be to put in a sufficiently sized boiler with a large indirect water heater and recirc that. That is a good system. If you are in a heavy heating area the boiler will also allow you to drive a radiant floor heat system. It is really nice to step out of the shower onto a warm floor.

I can't comment on your previous system as I don't know how it was laid out or how the recirc was controlled. I will say that I think your best option, the one you are dead set against, tankless, is still your best bet. Here's why. This home is 8000 sq ft. The conventional American design method is to put in a central mechanical area and run everything from there. This requires larger systems and a lot of piping to accomplish. You will be much better off if you break up the hot water system and install individual water heaters to supply different areas. I mean in, 8000sq ft the bathrooms may have different area codes. It makes no sense to operate off a central system. If you break up the system you get the benefit of everyone having hot water when they want it, no re-circ system requirements and excellent energy efficiency. This system will give you the benefits of tankless that you did not realize in the previous house. The units are compact and quiet. They will fit in areas around the house and you won't notice a loss of space. I just installed mine in a closet that measures 16X22". and brooms and dust pans are stored below.

Do you have any particular high flow fixtures? For instance large shower heads and body sprays? That has to be considered up front, regardless of the system you choose.

Thank you for the excellent advice. Can we put tankless into the attic above the master possibly? That would work great if it's possible.

The only high flow showerhead is in our master. Only 1 head but we like it to pour. :)

Can we do a hybrid? One big tank with recirc on the left side of the house to service the upstairs and downstairs. Tankless for our master and the guest bath under it on the right side of the house. That means no plumbing necessary between the left and right sides of the house?

So 2 separate circuits?

Or is that not how it works? Katherine

This post was edited by kath0000 on Fri, Oct 18, 13 at 20:13

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.

Thank you so much! I really appreciate your input.

Tub is Sunward 72" Whirlpool Bubblemassager K-1164-GW-0

Showerhead is Speakman Anystream S 2251 which we have now and adore. We take out water limiter.

We are in CA so no space under the house at all (slab foundation).

I am reading over all of your comments with great interest and taking notes. Meeting with builder next Fri so I want to have a plan. I wish I was not the only one thinking about these issues but apparently no one else seems to think this is going to be a problem but me. LOL.

Katherine

Looks like a luxury resort. Will there be a lot of folks staying there at any time or mostly empty?

If it's mostly empty except for a few times a year you may want to look in a valving sysytem.

If you don't mind me asking, I'm curious as to how much something like that is to build in CA with the crazy proerty/housing prices?