DIY outside storage tank

[Stumpuh]

I am looking for direction and feedback on the construction of an outside storage tank.
TANK..I have access to some salvaged 8"x18"x12' pressure treated timbers. My thoughts were to construct a 3 sided open top tank bolted to the exterior concrete foundation wall of my walkout basement. The interior measurements of the tank will be 9'8"x3'10"x 6'0".
INSULATION..My thoughts were to line the sides and bottom with ??" of insulation. This would provide a smooth surface for a liner. I could also shape the interior prior to adding the insulation if there is any benefit to something other than a rectangular tank with square corners?
LINER..I would need a source for a liner other than EPDM. Is it possible to just take a flat piece of material and fold it into the tank or more advisable to have one custom fabricated and if so, where?
HEAT EXCHANGER..Small diameter copper or PEX? Posibly a DIY site for either or both.
As you can see I don't have much, other then the desire to get back to heating with wood.
I have a "Controlled Combustion System" wood/oil boiler that I purchased in the late 70s. It was fine back then as this old farmhouse didn't have ANY insulation. As I rebuilt and insulated, the boiler became too much on the wood side. I'm thinking a storage tank would be the solution to overheating.
Any help would be appreciated.
Thanks, Stumpuh

 

[stee6043]

Is there any chance you could locate your tank inside? You will need mega insulation to have this tank outside. Non-pressurized storage tanks already have to deal with the inefficiencies associated with the heat exchanges. Placing it outside will further reduce the performance.

If you do a search here you will find lots of DIY tanks and HX coils. Most folks run copper as opposed to pex due to its vastly superior performance per foot of tube.

 

[btuser]

I also wouldn't try to attach it to the foundation. Just added stress on the wall/tank because if it wants to move just let it. Make your connections so expansion/contraction/settling can happen.