California Code, Corporations Code - CORP § 14314

(a) The system shall be adequate to maintain normal operating pressure of not less than 25 pounds per square inch, nor more than 125 pounds per square inch, at the service connection;  provided, however, that during periods of hourly maximum demand, or at the time of peak seasonal loads, the pressure may be reduced to not less than 20 pounds per square inch, and during periods of hourly minimum demand the pressure may increase to not more than 150 pounds per square inch.  Variations in pressure under normal operation shall not exceed 50 percent of the average operating pressure.  The average operating pressure shall be determined by computing the arithmetical average of at least 24 consecutive hourly pressure readings.

(b) The quantity of water delivered to the distribution system from all source facilities shall be sufficient to supply adequately, dependably, and safely the total requirements of all water consumers under maximum consumption, and shall be sufficient to maintain the pressure specified by subdivision (a).

(c) The distribution system shall provide at least one connection per service and, to the extent feasible, shall be designed in a property segmented grid so as to do both of the following: