rocket stove water heater for spa heating

hello all !
i just join your website and i cant find a rocket stove plan to heat the water of my spa/hot tub , since the rocket will be outside will it work in a cold climate ? as i live in quebec ,canada .
ps : it would run with a seperate pump and would be working with pellets , this way i wouldnt have to keep the water hot all the time with an electric heater as it is now but just heat it fast when ever i want to use it in the winter ...
any good ideas welcome ! ( excuse my spelling english learning in progress ...)

thank you ! denis lapierre
laval quebec canada .

I have all ways wanted to do this .
I would use a barrel run pipe around the inside.
fire in barrel able to cook above maybe.
insulating clay /adobe around outside.
make use of old pallets,paper,scrap wood.
hot tub inside green house maybe.
also below is some good post about rocket stoves.