We are having a 40CFM nitrogen generator installed soon and the company is recommending a 60gal bulk tank. This seems small to us, and we're wondering what size bulk tanks other breweries are using for N2? We're using N2 for keg washing (3 head unit) and purging our 30bbl brite. Also, they are recommending a food-grade aluminum tank with a sterile filter. Any recommendations on tank material and filtration?