The hot liquor tank or HLT is a brewing vessel used to heat water for different stages of the brewing process, including the mash and sparge. The hot liquor tank is typically heated by either gas, steam, or an electric heating coil. Depending on brewery configuration, the hot liquor tank may hold water at temperatures as high as 170° F or possibly even higher in cases where a boil is conducted to modify the mineral composition of the brewing water in order to remove bicarbonate
The photo below is the brewing configuration that I use. The hot liquor tank is the rightmost kettle, and I utilize a march pump to transfer the heated water to the mash tun at different times in the brewing process. Additionally, at the end of the boil I fill the hot liquor tank with ice and cold water and pump the cooled water through the counter flow wort chiller to cool the wort more quickly.