Tankless alternative for Master Bath? (Marathon for rest of house)

Hello all. Would appreciate your thoughts regarding the following. Project is new construction. Master shower is ~8x8' with multiple heads and body sprays, all together requiring ~12GPM. Practically speaking, average shower usage will require ~8GPM, as all fixtures rarely will be on simultaneously.

Property is serviced by 9GPM well (with reserve tank), and primary hot water source for most fixtures will be 85g Marathon tank.

I am considering plumbing the master shower (as well as the two master bath faucets and roman tub filler) stand-alone, with a dedicated exterior-mount tankless (LP) unit.

I am concerned that an 8GPM shower will drain the Marathon quicker than I will be able to leave for work in the morning before screams from wife wake the neighborhood.

I am distrustful of the tankless units (which may or may not be able to provide hot H2O rises year-round in central Virginia), but can not think of any better solution. Bosch 250SXO or similar Rinnai would be contenders...

Any thoughts much appreciated!

no problems

If money is no object , go for it

but I think something that will handle your flow

rate might set you back quite a lot of money.....


It would probably wiser and cheaper to install 2 -50
gallon gas heaters in series.....or a 50 and 75 would still be cheaper...

Go with a Noritz 13.2 and you won't have any trouble. The Bosch isn't really a top of the line unit, and it's price reflects it. However if your pump is only capable of 9gpm, don't you think you need to upgrade, and get a bigger pressure tank?

Thanks for the advice... I wish that I could use two tanks in series - but even 170 gallons (two 85g Marathons in series) would only provide ~30 minutes of continuous shower time - more than enough for me, but not enough for back to back morning showers... So, I definitely am going the route of a tankless, but as the above poster pointed out, only a handful of units are capable of producing 6gpm (the amount I figure I need, taking into consideration mixing hot and cold) with 50+ degree rises (central Virginia). Pricey project! I would not have gone down this path in hindsight. In any extent, thanks.