Abstract: A tank for use in a system that outputs a liquid at a user defined constant temperature in order to regulate the temperature of a piece of equipment includes a body of material having a top wall and a plurality of other walls which collectively define a chamber for receiving and storing the liquid. The top wall of the body of material has a manual fill port for pouring new fluid into the chamber and one of the other walls includes an outlet port for discharging fluid stored in the chamber. An auxiliary port is located on the manual fill port and a return fluid port is located on the auto refill port. The body of material further includes a well which extends down into the chamber from an opening in top wall of the tank and which can be removed. The well is sized to accommodate a deionizer cartridge. When the well is removed, either a heater or an immersion pump can be disposed within the chamber.