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Old 09-24-2012, 10:03 PM
jbell36 jbell36 is offline
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Pressure and GPM - Designing System

i'll try to make this short...if you have a 5/8 meter with 50 psi on one side of town and a 5/8 meter with 90 psi on the other side of town are you able to put more heads on the 90 psi even though the meter is only 'rated' for what, 12-15 GPM?
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Old 09-24-2012, 11:37 PM
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cjohn2000 cjohn2000 is offline
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Pulling too much water through a meter can "knock" it out of calibration. Obviously higher friction loss through the meter and pipe to and from, which would result in a lower dynamic.
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Old 09-25-2012, 11:24 AM
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Wet_Boots Wet_Boots is online now
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There are several flow-capacity standards for what you see as a 5/8 meter. The old standard was 20 gpm as maximum flow. Those meters are increasingly less common. A modern variation is a 5/8-3/4 meter, with the 30 gpm max flow rating for a 3/4 meter in the 5/8 package.
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Old 09-25-2012, 07:24 PM
muddywater muddywater is offline
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It would prob be safe to run 4 rotors per zone at 50 psi and 6 rotors at 90 psi. Using 2, 2.5, and 3 gpm nozzles depending on rotor radius. And if it hit the fan, you have room to nozzle down.
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Old 09-25-2012, 09:09 PM
jbell36 jbell36 is offline
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Quote:
Originally Posted by muddywater View Post
It would prob be safe to run 4 rotors per zone at 50 psi and 6 rotors at 90 psi. Using 2, 2.5, and 3 gpm nozzles depending on rotor radius. And if it hit the fan, you have room to nozzle down.
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this is exactly what i was thinking, but i wanted to ask because i'm usually wrong...on this particular system we have 7 heads on two of the zones and i can guarantee you we could put another 7 on...you can't even push the head down with your foot...we didn't design the system, but we did renovate it...the issue is it's on a huge hill and years ago when the house was first built the builder didn't backfill or pack the hillside properly and there was a landslide...i didn't find this out til later, because the design of the system made absolutely no sense, but when they told me this it all clicked...there was 40' of swing pipe at the bottom coming up at a 45 degree angle to compensate for the pipe/heads that slid down the hill...one lateral was only half way across the hill, so we had to install like 100' or something like that just to complete the system...

anyways, i was thinking while i was there how i would have designed the system knowing it was a 5/8 meter and knowing there is 90 psi...it just makes more sense to me that if you are able to put more heads on a zone that will cover adequately then why not...i just figured i would ask just in case there was something i didn't know about that i would be doing wrong
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Old 09-25-2012, 09:27 PM
muddywater muddywater is offline
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Quote:
Originally Posted by jbell36 View Post
this is exactly what i was thinking, but i wanted to ask because i'm usually wrong...on this particular system we have 7 heads on two of the zones and i can guarantee you we could put another 7 on...you can't even push the head down with your foot...we didn't design the system, but we did renovate it...the issue is it's on a huge hill and years ago when the house was first built the builder didn't backfill or pack the hillside properly and there was a landslide...i didn't find this out til later, because the design of the system made absolutely no sense, but when they told me this it all clicked...there was 40' of swing pipe at the bottom coming up at a 45 degree angle to compensate for the pipe/heads that slid down the hill...one lateral was only half way across the hill, so we had to install like 100' or something like that just to complete the system...

anyways, i was thinking while i was there how i would have designed the system knowing it was a 5/8 meter and knowing there is 90 psi...it just makes more sense to me that if you are able to put more heads on a zone that will cover adequately then why not...i just figured i would ask just in case there was something i didn't know about that i would be doing wrong
If it is a new neighborhood, i usually try not to max out gpms. Also keep in mind you lose/gain a 1/2lb of pressure per foot of rise/decline.

And on a long pipe run to the backyard you are going to have some pressure loss if it is 1" pipe. So if you are running 7 heads with great pressure right at the meter, then try to do the same 200' behind the meter and up an incline you could have a problem. I always try to be conservative... keeps me out of trouble and leaves the option to add a head in the future.
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Old 09-26-2012, 09:29 AM
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1idejim 1idejim is offline
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Quote:
Originally Posted by muddywater View Post
If it is a new neighborhood, i usually try not to max out gpms. Also keep in mind you lose/gain a 1/2lb of pressure per foot of rise/decline.

And on a long pipe run to the backyard you are going to have some pressure loss if it is 1" pipe. So if you are running 7 heads with great pressure right at the meter, then try to do the same 200' behind the meter and up an incline you could have a problem. I always try to be conservative... keeps me out of trouble and leaves the option to add a head in the future.
If you are being conservative use 0.433 per ft. instead of .5

6.70 psi per hundred ft. difference
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Old 09-26-2012, 10:15 AM
Kiril Kiril is offline
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Originally Posted by 1idejim View Post
If you are being conservative use 0.433 per ft. instead of .5
Careful man, you might upset boots.
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  #9  
Old 09-26-2012, 11:14 AM
muddywater muddywater is offline
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Quote:
Originally Posted by 1idejim View Post
If you are being conservative use 0.433 per ft. instead of .5

6.70 psi per hundred ft. difference
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You just had to google that didnt you
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Old 10-02-2012, 10:43 PM
muddywater muddywater is offline
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Quote:
Originally Posted by 1idejim View Post
If you are being conservative use 0.433 per ft. instead of .5

6.70 psi per hundred ft. difference
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Actually .5 is more conservative than .433 when going up an incline. I am banking on a 50 lb pressure loss with .5 and you are banking on a 43 lb pressure loss per 100'. 6.7 psi of gravy.
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