Looking for some input here on something I was noodling through while driving back from a parking lot deal I got on a 10 gallon Igloo water cooler that I had planned on using as just a HLT. When I was using a square cooler as a mash tun, I integrated a sparging arm into the lid that I think did a pretty good job of washing my mash of every bit of useful wort and I want to take one of the lid's of my 2 Igloos and do it again but I want to insulate the lid as I will be penetrating the lid to make a path for the pvc pipe that will be the sparging arm and to attach the arm to the underside of the lid. Additionally, now with a HLT that is going to be sitting on top of my 6 and a half foot brewing tower, running a pipe through a securely attached lid to fill the tank also sounds better and safer than hanging a hose over the side of the cooler or asking my pump to push it through the outlet and fighting all that head pressure. Here's the mod idea I want some input on....does anyone have experience with some sort of food grade "Stuff in a Can" or "Great Stuff" spray expanding foam insulation? I know there is one that's made for pond use that will not kill your fish but not having found a MSDS print out that says it's OK, I'm being cautious. If I was only penetrating the top, I would have no hesitation using the same stuff I used to fill in some cracks around where my HVAC lines come into the house but since I am penetrating the inside portion of the lid, I want to be ultra careful about not introducing any toxins to the brew.