Was doing some reading in my Turf Irrigation Manual (Watkins) looking for a formula and came across a section I'd hi-lited many years ago pertaining to designing systems with the anticipation of decreased pressure occurring in the future. Considering all the recent discussion on systems that have developed similar problems I thought I'd share a few passages for those that don't have this valuable resource book. "Gauged pressures in excess of 60 PSI should be especially suspect. Water distribution systems are designed in new neighborhoods to allow for building, extension of mains into even newer areas, and reduction of main capacity due to deterioration from aging. Thus, immediate pressure in a new neighborhood is usually substantially greater than the future low pressure. As a general rule, systems should be designed to operate on less pressure than the anticipated low pressure in new neighborhoods and known low pressure in older ones. This protects the system from anticipated pressure drops. When low static pressure is: Allow: Design for: 50 PSI 10% 45 PSI 75 PSI 15% 65 PSI 100 PSI 20% 80 PSI 125 PSI 25% 95 PSI A further argument in support of conservatism is the necessity to design systems to function properly on hot days when pressure will be lowest. This is obviously the time when good, dependable, artificial watering is needed most." Interpretation: Plan ahead!!!