(1) All slop-hoppers shall be fitted with approved hinged corrosion-resistant metal gratings having openings not exceeding 20 millimetres in width.

(2) The water-line shall be just below such grating, and the area of the surface of the water shall be not less than the area of the spigot outlet of the fitting.

(3) A second movable grating for the support of receptacles shall be used above the other, and shall have openings not less than 75 millimetres in width.

(4) Slop-hoppers shall not be constructed in two pieces unless the junction is above the water-line of the trap and the joint is constructed to render it firm and watertight.