And what makes anyone think that there is room, it's practical, to put
six water heaters in a typical house?

There are plenty of small water heaters that are designed to be placed in a
cabinet or under a sink, such as this one:

https://www.amazon.com/Bosch-2-7-Gal...ric-Mini-Tank-
Heater/dp/B0148O658Y

Obviously, a small heater like that isn't going to supply all of your hot
water, but it would take care of most quick tasks. Washing your hands,
rinsing a dish, etc.

You could certainly install six of these small heaters in most houses, but
it wouldn't make financial sense. Six small heaters would cost $960, not to
mention the electrical and plumbing upgrades needed to support them.

A traditional recirculating system is easier to use, takes up less space,
and would probably be cheaper in the long run.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com