18-29-604.10.1.3 Available pressure.
   In determining the available pressure to overcome friction in the piping system, head meter and other losses shall be deducted from the minimum available pressure source. When the pressure exceeds 100 psi (690 kPa) at any plumbing fixture, the pressure shall be reduced by an approved type reducing valve. The minimum size of fixture supply pipes are shown in Table 18-29-604.5.