Each fixture shall have a liquid seal of not less than 2 inches (50 mm) and not more than 4 inches (100 mm), or deeper for special designs relating to accessible fixtures. Where a trap seal is subject to loss by evaporation, a deep-seal trap consisting of a 4-inch (100 mm) seal is required, or other means shall be provided to prevent loss of trap seal. Other means shall include: automatic trap seal primers conforming to ASSE 1018 or ASSE 1044, or vegetable or mineral oil added to the trap.