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Adjusted Static Pressure

1K views 5 replies 3 participants last post by  YardPro 
#1 ·
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!!! :)
 
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#3 ·
Thanks. Maybe I'll post it in the sticky thread too.

A good designer will prepare for the future. A shoddy one will say, "Heck, when the pressure drops and their system no longer works then we'll get more money out of them on a redesign." :dizzy:
 
#4 ·
Interesting, Jon. From the Sequim city web site. :)

"How do I find out what my water pressure is?"

"Call Public Works Department with your address and we will provide you with the water pressure or assist you in getting your water pressure for you."
 
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