Originally Posted by Rain Man
I'm going to sound like a nut job when I say this, but remember that I'm a child of the Cold War.
I kind of like having a tank in the house, because if there's some sort of major emergency it's a good water supply for a couple of days.
Not at all, it's a great idea to have available potable water available. One thing I recommend to people if their existing tank isn't leaking, is to have it before the on-demand and have the breaker off, this functions as a storage tank that slightly increases the inlet temp of the on-demand and allows greater water flow. Also functions as available drinking water, just make sure to filter the water if you take it out of the bottom of the tank as the sediment can be pretty gross.
In the case of no gas, you can turn on the breaker and have hot water.
Install an isolation valve kit with any on-demand unit. Rinnai is including them into the units now.