I am building an addition with a basement underneath. The existing home is on a slab foundation, and the 20 year old tank water heater is in a closet. I was planning to replace this water heater with a tankless heater in my new basement. However, I now realize that this will significantly increase the distance from the water heater to the kitchen (and a couple bathrooms).
The new plan that I am forming in my head is to put my large tankless water heater in the basement to service the new bathroom/laundry room in the addition directly, and in series (where the original tank heater was) put a much smaller tankless heater that is near the other two bathrooms and kitchen. The thought being that the smaller one will shut-off when the water from the larger heater reaches it, but it will provide hot water quicker to the faucets/shower much farther from the large heater. Is this a bad idea? Are there any other ideas that I should consider? (I've considered a recirc pump, but it seems that sort of defeats the purpose of tankless since it is always keeping hot water in the lines - your tank just becomes the lines).
Note: my tankless water heaters would be propane fueled