This rig sat outside my local HEB supermarket for quite awhile. I got some pics of it before they came and took it home. It seems to be made from 2 water tanks: I've never seen another like it and didn't catch this one in operation. It looks like the fire is built in the lower section and the 2 vertical pipes take heat to the second chamber. I didn't open it up to see if both are made to hold fire but they probably do.