We are remodeling a bath for our son who is disabled. As a part of the remodel, we are adding a 6' whirlpool/air spa tub, so that he can "soak" in the tub at times.

We currently have a 50 gallon condensing hot water heater (about 10 years old - put in during construction of the house).

I am thinking about replacing the water heater with a tankless. We have a Takagi Jr. on the other side of the house (guest bath, laundry, kitchen) and it works great, with the typical problems of cold water sandwich and long start up times to get hot water. Not a big deal on that side of the house.

The 50 Gallon supplies 3 bathrooms, which is what the tankless would replace. My concern is that to fill the tub, 50 gallons would not be enough, and kind of defeats the purpose of having the tub !

I am looking at the Eternal (GU145) but have not found a lot of good reviews lately on these. It looks like it eliminates the "cold water sandwich" with it's onboard mini storage, which is what draws me to it. I CAN'T have the sandwich, or my wife will KILL ME !!

I would love to hear suggestions/recommendations. Efficiency is important, but I want something that will work and last!