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Tom

Supreme Member

11

Saturday, January 17th 2004, 4:06am

Ray, do you know how to calcuate the pressure loss in a sprinkler system?
Do you understand the difference between static and dynamic pressure?
Do you understand that at a given gpm you will have a pressure loss associated with pipe, fittings, valves, backflows etc? These losses add up in a system to the total pressure loss of that system.

drpete3

Supreme Member

Posts: 375

Location: USA

12

Monday, January 19th 2004, 3:52am

The components obviiosly add up but how do you assign valuesw to each component? Also when hunter gives me a chart on their pgp and cross referrences psi with gpm is that referring to static or dynamic pressure?
Thanks,

Pete

Tom

Supreme Member

13

Monday, January 19th 2004, 10:43am

charts always refer to dynamic pressure, because there is a flow associated with it. when you hook up a pressure gauge to say your outdoor faucet you are reading the static pressure (there is no flow occuring). as you in crease the flow (open up another faucet) the pressure becomes dynamic and will be less than the static.

Pressure and flow are related.............as the flow increases the pressure will decrease.


Tom

Supreme Member

14

Monday, January 19th 2004, 10:45am

you asked about assigning a value to each component, almost all sprinkler catalogs, books etc. have pressure loss tables in them.

drpete3

Supreme Member

Posts: 375

Location: USA

15

Tuesday, January 20th 2004, 6:48am

so what you are saying is that their is no dfference between static and dynamic pressure except that it may decrease as the water begins to flow.

I will look for these tables.
Thanks,

Pete

Tom

Supreme Member

16

Tuesday, January 20th 2004, 9:51am

theres a huge diff- static pressure=no flow, dynamic pressure=flow

drpete3

Supreme Member

Posts: 375

Location: USA

17

Tuesday, January 20th 2004, 9:54am

In what specific applications is there a difference. Pressure is pressure. 40psi static and 40 psi dynamic still exert 40 psi in all directions.
Also Tom why should I cycle my zones?
Thanks,

Pete

rain man

Active Member

18

Tuesday, January 20th 2004, 3:47pm

hey hey now...eazy fellas. just thought I would throw my 2 cents into this heated debate.
static pressure is pressure of water at rest...i.e. what you start out with. Once that valve is opened static pressure becomes dynamic pressure or pressure of water in motion, and will decrease due to a number of factors such as friction loss, valves, increase in elevation etc. It may also increase due a a loss in elevation.
In everyday life we should be using static pressure as a starting point to determine the dynamic pressure driving our sprinklers and rotors so that everything sprays evenly and to the desired radius.

drpete3

Supreme Member

Posts: 375

Location: USA

19

Wednesday, January 21st 2004, 5:36am

I didnt mean for my reply to sound rude I just wanted to be sure I wasnt missing somthing and I am a person that will question somthing until I understand, especially matters of physics.

What about the zone cycling. I am not clear on this matter.
Thanks,

Pete

rain man

Active Member

20

Wednesday, January 21st 2004, 3:56pm

the reason I would cycle my zones is to keep runoff from occuring. the whole Idea is to conserve water so if you overload a zone by watering all at one time you will lose water to runoff. It is also very hilly were I live. Not sure why else, although 75 minutes seems very, very, long to run a single zone.

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