When your hot tub goes down and the spa pack is in for repairs, most people will wait the week while it is the shop.
Not to be dissuaded from using his hot tub for anymore than a couple of days, Mr. Inventor found another way to heat the tub. He took and an old auto propane tank, you know, as most people have one kicking around, put in a bunch of copper pipe and utilized the exisiting fuel in/outlets that were in place for water.
He thought, "Why have all that wood heat and not make hot water too and hot water for my hot tub?"
A $400 trip to Home Depot (is it always a $400 trip for you too?) and 14+ hours later, he has water circulating from the hot tub back into the woodstove where the fire heats the water and back into the tub again. It warms up much faster that with the spa pack actually. The only problem is TOO MUCH hot water. "I'll make a steam room!!"
OK, great idea Honey, but plastic walls do not a steamroom make 'cos when you brush up against them, the water is COLD!! That and hose went crazy under pressure and came alive, kicked back and somehow burnt my hand...("That's because you didn't listen to me" he chirp. Certainly not because not because his design was at all flawed.) "I need to make a Steam Engine now --then we can get off the grid!" Sigh. God love him for having enough ambition to try. And it IS heating up the water in the hot tub quite nicely to boot!
He welded on fins (where the black lines are on the top photo) to increase the area and heat distribution. Outside with a bit of re-design he has put this assembly of valves and hoses together plus an steam overflow so should it get too hot and build up steam pressure, it has a place to go into a metal resevoir. God forbid anymore of my body parts get burned.
All in all to get one more piece of equipment that isn't dependent on shore power is a good thing.
Now if he can stop the smoke from billowing back out when you load the flippin' wood in, it'll be perfect.