No reduction in water charges shall be made for leakage except in cases where it shall appear, on investigation, that the leakage is underground and not subject to detection by ordinary methods, and where, further, the owner and other occupants of the premises are free from negligence in causing or failing to report the leakage; excepting, also, in cases during periods of emergency, when, by reason of shortage in materials or manpower, immediate repairs are not available, where the owner has made diligent efforts to provide the repairs and has actually employed a plumber to make them, in which cases an allowance of time of not to exceed 30 days may be granted to permit the plumber to complete the repairs. No reduction for leakage shall be permitted in an amount in excess of 50% of the water bill as rendered. ('80 Code, § 52.33) (Ord. 5-49, passed 3-29-49)