Be careful with the first hour ratings. On a 100 gal tank you will get about 70-75 gallons of hot on that first load. You then get the balance of the first hr rating over that first hr. For the kind of lay-out you suggest I think you should split the house up into two systems and try to centralize each tank to its load. That minimized pipe losses with the recirc, and yours will be substantial. The very best recirc system is the Metlund Design system. It complies best with all the new Title 24 regs. You will need 3/4" insulation on your hot piping. Again T24. Be very careful with the pex sizing. I re-piped with Uponor and the brass fitting here in the Foothills of N CA. There is a bushing affect on the fittings. The ID of 1/2" is 3/8, 3/4=9/16 and 1" is 13/16. It does make a difference. I have a couple faucets I was surprised how poor the pressure is on my current well 40-60 psi set-up. I had intended to go to a constant pressure well pump but now will definitely do so. Everything is good about the 50 psi range. Not so at 40#

I am a fan of tankless. I represented a major manuf of tankless for 20 yrs. As far as your suggested products I will only suggest that you avoid Bosch. They, imho, do not have the right technology. Your first step regardless of what you do for equipment is a thorough water test. Manuf of tankless have to list annual cleanings for maintenance, but I had one unit for 12 years and never touched it. It was a pre-production model and I had to replace it prior to selling the house. I cut it in half and it was as clean as a whistle. Many of your plumbing questions and answers begin with the compete water test.

Tankless (2) could handle your loads until you bring the tubs into play. They represent a massive load, even for your Vertex's. To handle your tub flows you should have two units on each side of the house. The thing about the tankless is they will each make your 7 or so gpm 24 hrs per day, but 135/7=about a 18-20 min fill. Will you wait that long for your bath. I have a bath fill controller on my tub. I set it at 104 and 35 gal (the vol of my tub) and it will deliver 35 gal of 104* water and shut off the hot and beep to tell me my bath is ready. Pretty cool actually. Your shower should be okay with one tankless, but your shower head(s) must fall within the flow capacity of the water heater.

I can go on and on with this topic. Get your water tested and report back. That should be step one regardless of what your are doing.

Better talk to a plumber. There's a lot more water restrictions this year in CA than last year, and you are gonna be challenged to comply with that with all of your high use fixtures. You may not be able to implement your plans without changing to smaller tubs and less numerous sprays than you plan.

Yeah, I heard about this. I'm not so concerned about the tub as we only have the one filler. It's not a jacuzzi type. The shower OTOH has 3 heads and that may be a problem. We're trying to figure a way around that :-)

The way around it is to rough it in to code and get your rough in inspection. Prior to Sheetrock you have your plumber modify the shower to your specs. Once you have your final you install your other shower head body sprays etc. Talk to your plumber about this as well.

Then when it's time to sell the house and sign the disclosure about whether the seller is aware of any work or conditions not in compliance with code, what do you suggest Jack?

Any disclosure (even something that a buyer might agree with) can cast doubt about what else was done but not mentioned. Not a good idea.

Shhhhh......I wasn't going to talk about this even LOL.

I'm not the least bit worried about "casting doubt". NO ONE wants what's in the stupid 2014 regulations except the rabid environmentalists. EVERYONE wants a good hot shower.

Shhhhhhhhhhhhhhh

Snidely, I understand totally what you are saying. It was intended in more of a joking manner, but joking on-line is tough. Thank you for pointing this out. You are correct.

I once had to visit a fantastic home that the guy had built a shower that required 25gpm. All the owner could tell me was his shower head was $6,300. He couldn't understand why it couldn't deliver the water he needed for $6,300.

Btw, this is the way people who insist on these hi-flow fixtures are doing it in CA where the new codes require a max of 2.5 gpm in a shower. That is total flow, not each head. As dry as it has been here my new bathrooms meet the code. To each his own though, so if he wants this, I have described the method.

I'm a Californian, I agree about the idiocy of some laws we have and the idiocy of some laws we don't have. But it is what it is. Changing little things after an inspector leaves has been a common practice for ages, it's just that the disclosure rules add a different dimension. Personally, I'd probably have no problem disclosing that some plumbing was changed but that everything else was spit and polish. There's nothing to lose with the whole truth.

Some years ago, a friend bought a pretty pricey house (>$1 million at the time) near Truckee. It was an older house that had been renovated and substantially added on to. After some odd experiences with electricity (flickering lights), he called an electrician. The guy looked at the panel and behind some wall plates and suggested that the wiring had some problems and seemed amateurishly done. Sensing greater problems, the guy had a general contractor buddy come up to poke around. It turned out, the whole addition had been an unpermitted DIY project of the previous owner and there were substantial problems of all types - plumbing, structure, etc.. The unpermitted work was not disclosed by the seller. My friend sued and won a prompt victory. The outcome was a tear-down and rebuild of the addition, at the sellers' expense, BECAUSE of the non-disclosure.

An extreme case, and really not relevant to OP's situation, but interesting all the same. The disclosure rules have bigtime legal significance.

As it turns out our permit was issued in 2013 so according to my contractor we only need to comply with 2013 regs. WIN!

Not sure if this works for your situation. We raised the temperature in the HW heater. We use more cold at the mixing valve and the hot water lasts longer...... We do have pressure balanced valves so we dont have the whooo effect when a toilet is flushed.......