I built my Brewery from vessels that were used to make medical test batches. The stainless steel tank on the left is the Hot Liquor Tank it can hold 15 gal of water. Inside the tank is a copper coil used as a heat exchanger. The center vessel is the Mash Tun it is made of medical plastic and can hold about 100 Lb. of grain. In the bottom there is a Stainless Steel screen that acts as a filter to keep the grain in place while circulating the liquid. The stainless steel vessel on the right is the boil tank that can hold 30 gal of wort, this tanks also has a stainless steel screen for hops and Trub screening. My system is called HERMS which stands for Heat Exchange Recirculating Mash System. With a HERMS setup a heat exchanger is installed in the Hot Liquor Tank (HLT) and a pump circulates liquid wort from the mash tun through the heat exchanger then back into the mash to maintain the mash temperature. Maintaining and changing mash temperature is important for the conversion of starch in the grain to a sweet liquid. When the Sweet liquid has converted and does not contain any starch. It gets pumped into the boil tank. check out process of Making beer