Valves for connections to holders including relief valves for pressure tanks shall be inspected and tested for opening, closing and leakage at least twice a year. All necessary adjustments and repairs shall be made to restore each item to a high operating efficiency. Gate valves on inlet and outlet connections shall be tested for free movement, and inspection for lubrication of stems and condition of packing at least once a week. Where practicable, control valves shall be provided on inlet and outlet connections at a point distant from the holder, and inlet, outlet and by-pass valves shall be motorized. All piping in proximity to holders shall where practicable be placed underground.