cln wrote:
I've seen a system lately that will wrap around your drain pipe and
extract the heat for drain water (shower or tub) and converted to more
heat.

I don't have the link now but if its worth selling a system I think
leaving the water in the tub is a great idea! With my crackling dry
hands I could use the little extra humidity myself.
cln
Hmmm,
My gosh! Install a power humidifier and get it over with.