Sec. 503.2. System pressures

(a) System pressures.

Minimum working pressure (the pressure under all conditions except fire flows) in all portions of the water corporation's distribution system should not be less than 35 pounds per square inch (psi). Additionally, for new water plant construction designed to serve five or more customers, the minimum design pressure should also be an amount that, upon calculation, would theoretically be sufficient to maintain 15 psi at an 8 gallons per minute (gpm) flow at the meter. If this condition is not met, but the pressure on the company's main in the immediate area satisfies the 35 psi requirement (or has been exempted from such requirement by the commission), it will be the responsibility of the developer/owner of new properties requesting service to make all modifications necessary to meet the pressure and flow standard required at the meter. The maximum customer pressure at the building line should be 100 psi, except where differences in elevation require pressure higher than 100 psi in order to meet the minimum working pressure in other parts of the distribution system. In such cases where the system pressure exceeds 100 psi, the company should attempt to reduce the pressure to 100 psi by creating a separate pressure zone or installing pressure-reducing valves in the distribution system. If a company can demonstrate that this is impractical due to excessive cost or engineering considerations, the customer will have the option of installing an individual pressure-reducing valve. The customer exercising this option will be responsible for purchasing, maintaining and replacing such valve, and all costs associated therewith.

(b) Monitoring requirements.

Each water corporation shall have the necessary equipment to record an individual customer's pressure and to make pressure surveys and record at least a 24-hour continuous test. Each water corporation shall monitor the system pressure in each pressure zone at or near the point of highest elevation in the zone, where the lowest pressures can be expected to be experienced, and shall report to the department on a monthly basis each instance when the pressure drops below the minimum working pressure as previously specified for a period of four hours or longer. Likewise, pressure will be monitored in each pressure zone at or near the point of the lowest elevation in the zone where the highest pressures can be expected to be experienced. This monitoring requirement may be satisfied by using the readings taken at one of the water corporation's regular operating stations provided that the water corporation can demonstrate that it can accurately extrapolate the pressures at the highest and lowest elevations from such readings.