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Posted by J.A. Michel on September 2, 2006, 9:18 pm
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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Posted by Edwin Pawlowski on September 2, 2006, 10:48 pm
> 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.
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.
>
> 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?
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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Posted by zero on September 2, 2006, 11:33 pm
>
>> 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.
>
> 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.
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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Posted by Edwin Pawlowski on September 3, 2006, 12:19 am
>
> 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. ;-)
>
That is what it says on page 420. What is his gpm then?
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Posted by zero on September 3, 2006, 12:44 am
>
>>
>> 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. ;-)
>>
> That is what it says on page 420.
Rip 419-421 out then. ;-)
>What is his gpm 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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