(1) The water system physical capacity shall be established by evaluating the capacity of each system component such as source, treatment, storage, transmission, or distribution, individually and in combination with each other. The evaluation shall identify any limitations on the ability of the system to provide service to all consumers.

(2) The water system physical capacity shall be:

(a) Reported in terms of total equivalent residential units (ERUs) and the number of residential and nonresidential connections with the number of ERUs they represent; and

(b) Compared to the existing number of residential and nonresidential connections currently served and the ERUs they represent.

(3) Total source capacity calculations shall not include emergency sources as defined in WAC 246-290-010.

(4) Total daily source capacity, in conjunction with any storage that is designed to accommodate peak use periods on a daily or longer basis, shall be sufficient to provide a reliable supply of water equal to or exceeding the MDD.

(5) Treatment capacity, in conjunction with any storage designed to accommodate peak demand periods on a daily or longer basis, shall be sufficient to provide a reliable supply of treated water equal to or exceeding the MDD while meeting the water quality parameters set forth in Part 4 and Part 6 as applicable, of this chapter.

(6) Water storage shall be sufficient to meet expected system service demands by providing sufficient operational, equalizing, standby, and where applicable, fire suppression storage volumes in accordance with WAC 246-290-235.

(7) Distribution system capacity shall provide for PHD, or MDD plus required fire flow, as required in each pressure zone while maintaining minimum design pressures established under this chapter.