A third type of collector, integrated collector storage (ICS), is worth mentioning. As the name suggests, these collectors hold a comparatively large volume of fluid (40 gallons or more). Usually, though not always, this fluid is the domestic—or end-use—water, rather than a separate heat-transfer fluid. However, many ICS collectors are appropriate only for installation in areas that have record-low freeze temperatures above the single digits, and less than 30 to 40 freezes per year. While the volume of water in the collector is frequently able to hold enough heat to resist freezing, the piping to and from the collector, if not installed and insulated properly, is most likely to freeze and burst. Furthermore, cold nighttime temperatures result in heat loss, since the end-use water is stored outside in the collector.
