L.D.
Hi,
I am soooo sorry to hear you flooded. My husband does HVAC and has installed tankless water heaters,, when I saw your post I asked him what input he had and he said he would be more than happy to answer any questions you have.
He is very honest, and if you use him or not, he is happy to give you some advice. His e-mail is ____@____.com Luck!