When in running pipe it is necessary to cross wood joists or beams, they should be notched as little as possible and shall not be notched to a depth of more than one-fifth (1/5) of the depth of the timber. The notching shall be as close as possible to the point of support of the timber and shall not be further than three feet (3') from a support. When feasible, the piping should be run so that only timbers having the shortest spans shall be cut. (Ord. 15.28)