There should be a provision for adequate drainage facilities in a hot-water heating system during shutdown periods. Pitching all pipes to a central point is an important consideration in designing the system because it is essential to effective drainage. If drainage is not provided for, there is always the danger of the unheated water freezing in the pipes during extreme cold weather. In most installations a manual drain cock is installed at the lowest point in the return line just before it reaches the circulating pump (see Figure 7-29). Chemical antifreeze solutions have also been developed for use in hot-water heating systems in an attempt to prevent the water from freezing during shut-down periods.