my thoughts on a 10inch were because I live in ohio it might be 50degrees in December one day and -20 the nexted day I was thinking a 50 gallon water jacket with a pump it will be an open system with a pressure relief valve the main reason I want it so large is recovery it will heat my home and domestic hot water if and the main things I am wondering is the water jacket size large enough to transfer heat efficiently or should it be bigger I know the exhaust gas needs to be around 200 degrees just not sure what size I should make it saftey will be figured in with it being an open system there should be no concerns with it blowing up or boiling dry it will have a fill tube and have a 500 to 1000 gallon capacity so I won't have to fire it more than twice a day not sure if I want to go with tanks in my basement or outside yet any info would be great