Confused about GPM - New Sprinkler System

I'm designing a sprinkler system for my yard. This will be a fairly complex system, as the area to be watered is fairly large. I'm going to DIY install the system. I have a good handle on most everything that needs to done, however, I need help determining my available flow in GPM.
I checked pressure at an outside faucet, and have a static 62 PSI. I checked flow at the same location and have 8 GPM. I was doubtful of the 8 GPM reading, because that sillcock is supplied by a 1/2" pipe. So I opened up the shower and bathtub, and ticked off 14 GPM by using a timer and watching the gallons go by on my watermeter in the basement.
So, which reading is correct? Is there a better, more accurate way to determine GPM? I really want to get this right. I have a 1" watermeter, which has a full 1" ID poly supply pipe. The supply pipe is 50 ft. long, from the street to my house.
Second question: The spot where I plan to tap for the system is about 4ft after the watermeter. The pipe is 3/4" copper. To maximize flow, should I replace the 3/4" with 1"? Or will such a short length of pipe matter? I plan to use 1 1/4" PVC going to the zone valves as well. Is this OK?
Thanks for any advice!
J.A. Michel
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Neither of your measurments is accurate because of restrictions in the valves. You need to measure the flow at the open end of the pipe.
According to my Pocket Ref, a 1" nozzle at 60 psi can have a flow rate of 232 gpm. There will be friction losses too. A 1/4" nozzle would have the 14 gpm that you measured. Considering the opening at the valve stem, that may be correct. Even your water meter will have some restrictions in it, as does your main valve.

The flow will be restricted by the smallest pipe diameter on the water's path. The 1 1/4" going to the zone vales will not improve anything. Changing the 3/4" line will only help if the meter is not restricted down to that size.
There are other ways to assure the flow you need. Since you have zone valves, set the timer to do different zones at different times. Not every portion of your lawn needs the same amount of water anyway. An please, don't be like some of the idiots that have the sprinklers on in the rain.
Smarter would be to plant a yard that does not need added water to thrive. As water becomes more difficult to supply, large yards with perfectly manicured lawns will be looked on by society in the same category as smokers and Hummer drivers.
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That would give you a velocity of almost 90 feet per second providing you can overcome a 3000 ft. of head (1500 psig) friction loss!
Try turning the pocket reference upside down and read it WITH your glasses on this time. ;-)
-zero
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That is what it says on page 420. What is his gpm then?
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Rip 419-421 out then. ;-)

I don't know. There's not enough info to tell. With the known Cv of the meter you could at least tell a little more,,, but it sounds like he's thinking to spray the whole yard at one time!
-zero
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What additional information would be helpful? I'm planning on holding my zones to 10 GPM. Just trying to make sure I would have 10 GPM available so that each zone would operate properly.
J.A. Michel
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232 GPM? Maybe from a fire hydrant, but not a house. Perhaps it's 23.2?

Agreed. The short section of 3/4" will be replaced with 1" copper, and main to the zones will be 1"pipe.

Agreed. I'll try not to.

I have no yard right now. Anything I plant will require water.

Spare me the tree hugger bullshit!!
I want a really nice green perfectly manicured yard, and I don't rightly give a shit what the tree-huggers say. That's why I'm putting the system in.<duh> I also am a smoker, if that makes a difference. My employer has a major contract to machine parts for a fire supression systems that are installed aboard HumVees. Those Hummers are wonderful vehicles, which are bringing home our men and women in uniform who would have otherwise come home in a body bag. If someone wants to drive a humvee on the street, that's fine with me! It's their money after all. The tree huggers that whine about hummers are just jealous that they can't afford one.
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No, 232. As for a hydrant:
http://www.firehydrant.org/info/faqs_ask7.html Our hydrants are pressurized (in general) at about 60 PSI (and flow at about 750 GPM at that pressure), and have varying flow capacities. In pumping to a remote fire we want to maximize water flow to the site, and we have a few options:
First, we can hook up the hydrant to the pumper at the 4.5" discharge with an adapter and a 6" cloth hose (soft suction). The pumper has upper limits of 1500 GPM and 150 PSI, and the 4" hose line we are feeding from the pumper has a pressure rating of 180 PSI.
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I have a good handle on most everything that needs to done,

This should cover just about everything http://www.irrigationtutorials.com/sprinkler00.htm
-zero
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Your water pressure, 62 psi is a needed figure. With no flow, it is the same as the pressure in your water main. The flow at a tap is not a useful figure.
Given that you are tapping your incoming service near the meter, your procedure will be something like this --
1. Lay out a pattern for one area assuming a pressure of about 20 psi (possibly more) at the sprinkler heads. Total the delivery in gpm (gallons per minute) for all the heads on the branch. Then determine the pressure drop between the water main and the sprinkler heads (more later). If that drop is more than 62 minus the pressure at the sprinkler heads (possibly 62 - 20 = 42 psi) you must reduce the number of heads on the branch. If it is less you may be able to add more heads, but its best to have some reserve pressure in the system. You can always reduce the pressure at the sprinkler valve.
The pressure drop between the main and the sprinkler heads depends on the flow rate in gpm and the pressure losses in the water meter, piping and valves in the line. You get appropriate information from the people who sell you the hardware. Generally, valve and sprinkler manufacturers provide good data sheets to use with their products. I think that the drop in pressure in the meter at a large flow can be about 7 psi. Drop through sprinkler valves is about the same. The pressure drop in pipe depends on the type, diameter and length. Generally, 3/4 inch pipe is used. Long runs may require larger pipe or a lesser number of sprinkler heads.
Pressure drops in meter, valves and pipe increase dramatically as more flow is demanded. It's a square law relationship so if you were to increase the flow 40%, the pressure drop would double.
By sure to get the sprinkler manufacturers data sheet. The information it provides is essential.
SJF
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J.A. Michel wrote:

http://www.irrigationtutorials.com/sprinkler00.htm Very complete workup.
R
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J.A. Michel wrote:

http://www.irrigationtutorials.com/sprinkler00.htm
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