Subject to the provisions of subsection (2) of section 20, where a separate cold-water storage tank is installed—

a) If such storage tank is used to supply a hot-water apparatus and a bath, the cold-water supply to such bath shall not be connected to the storage tank at a point lower than one-half the depth of the storage tank;

b) Any separate cold-water storage tank, if fixed in a roof, shall be placed within a metal tray having sides at least 70 millimeters deep, and being of such dimensions that a space of at least 70 millimeters exist between the sides of the tray and the outside of the storage tank;

c) The tray shall be provided with a discharge-pipe of larger diameter than the storage tank-feed, and shall be so situated as to permit ready detection of the discharge of water.