I was all ways impressed with my granddad. Back in 1980 he moved us into a mobile home. First thing he did was go to scrap yard and pickup a wood burner with back boiler. Plumbed it into the existing boiler tank. Sorted out chimney out the side of the caravan. It saved a fortune and gave us nice hot water and heat. But I can remember that tank bubbling like hell when it hit boiling gurgling away and making all sorts of noise. Nothing bad ever happened though.