Has anyone built an indoor water heat storage tank? I'm planning the installation of a Tarm wood boiler. Tarm has an 822 gallon insulated tank for about $1900. Besides being expensive, it's round and would take up quite a bit of space in the basement. I'm thinking of building my own tank using plywood, angle iron for exterior bracing, foam insulation, and a EPDM liner. It needs to be about 4'x4'x8'. The Tarm tank uses High Temp extruded urethane rated at r-14. I'm just starting to do the research on what type of foam to use and where to find the EPDM liners. If anyone has done this and/or has information available to share it would be most appreciated.