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Posted by on November 2, 2006, 4:14 pm
I'm trying to figure out the maximum Flow GPM for my sprinkler system.
On the sprinkler (Rainbird 1800 series) it shows a chart listing the
PSI, the radius of the coverage area and the Flow GPM. For example,
the bottom entry on a quarter circle sprinkler is listed at 30 PSI, 14'
radius, and 1 GPM. Is this the maximum GPM the sprinkler will emit?
If my PSI is 60, twice the PSI listed on the sprinkler, will it double
the Flow GPM to 2?
My water line's PSI tested between 50 and 60, and the flow is 11.5 GPM.
It seems like I'd have to install a lot of valves to keep the GPM
within limits, and all for a very small lawn. :/
-Fleemo
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Posted by Edwin Pawlowski on November 2, 2006, 4:23 pm
> For example,
> the bottom entry on a quarter circle sprinkler is listed at 30 PSI, 14'
> radius, and 1 GPM. Is this the maximum GPM the sprinkler will emit?
> If my PSI is 60, twice the PSI listed on the sprinkler, will it double
> the Flow GPM to 2?
No,m it won't double. Does the chart have a way to plot waht you need?
>
> My water line's PSI tested between 50 and 60, and the flow is 11.5 GPM.
> It seems like I'd have to install a lot of valves to keep the GPM
> within limits, and all for a very small lawn. :/
Why a lot of valves? All you need is a pressure reducing valve if you don't
like hte pattern the sprinkler head is giving you. . Don't confuse volume
and pressure. While they have some dependency on each other, you use
different methods to control each.
If the lawn is that small, jut use a plain old hose and sprinkler for $5.99
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Posted by on November 2, 2006, 6:11 pm
fleemo17@comcast.net wrote:
> I'm trying to figure out the maximum Flow GPM for my sprinkler system.
> On the sprinkler (Rainbird 1800 series) it shows a chart listing the
> PSI, the radius of the coverage area and the Flow GPM. For example,
> the bottom entry on a quarter circle sprinkler is listed at 30 PSI, 14'
> radius, and 1 GPM. Is this the maximum GPM the sprinkler will emit?
> If my PSI is 60, twice the PSI listed on the sprinkler, will it double
> the Flow GPM to 2?
>
It's been 5 or 6 years since I did my sprinklers, let's see what I
remember. I think the pressure number on the sprinkler represents the
minimum pressure that the sprinkler needs to operate reliably. The flow
rate represents the maximum flow for that sprinkler head with the screw
cranked wide open to achieve the 14' radius. I think once you're past
the minimum pressure required to operate the sprinkler, the flow rate
is relatively constant.
The sprinkler manufacturers (Toro, Rainbird, etc) usually produce a
brochure to assist you in planning - you can probably find one in the
sprinkler section of your local BORG. In there, you'll find a chart
that summarizes the flow rates that can be supported with a given
supply pressure and a given supply pipe size (1/2, 3/4, etc). Use that
chart to determine your supply pipe flow rate in GPM, and add up the
GPMs of all your sprinkler heads. If your total demand is less than the
supply GPM, everything can go on one circuit. Otherwise, split it up
into separate circuits.
Hope this helps,
Jerry
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Posted by -zero on November 2, 2006, 6:54 pm
> I'm trying to figure out the maximum Flow GPM for my sprinkler system.
> On the sprinkler (Rainbird 1800 series) it shows a chart listing the
> PSI, the radius of the coverage area and the Flow GPM. For example,
> the bottom entry on a quarter circle sprinkler is listed at 30 PSI, 14'
> radius, and 1 GPM. Is this the maximum GPM the sprinkler will emit?
> If my PSI is 60, twice the PSI listed on the sprinkler, will it double
> the Flow GPM to 2?
1 gpm @ 30psi roughly gives a Cv of _.179_.
60 psi gives you something like 1.5 gpm.
Try calling Rainbirds help line.
-zero
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Posted by on November 3, 2006, 10:47 am
-zero wrote:
> > I'm trying to figure out the maximum Flow GPM for my sprinkler system.
> > On the sprinkler (Rainbird 1800 series) it shows a chart listing the
> > PSI, the radius of the coverage area and the Flow GPM. For example,
> > the bottom entry on a quarter circle sprinkler is listed at 30 PSI, 14'
> > radius, and 1 GPM. Is this the maximum GPM the sprinkler will emit?
The chart means that at 30PSI, set to a 14' radius, it will put out
1GPM of water. Many of these have nozzles that can be changed, so they
have tables showing the flow for the various nozzles and supply
pressures.
> > If my PSI is 60, twice the PSI listed on the sprinkler, will it double
> > the Flow GPM to 2?
No, it will be higher, but not double. There should be chart entries
for enough pressures so you can either determine it, or approximate it.
However, I've found that actual measured can vary quite a bit from
the rated values.
>
> 1 gpm @ 30psi roughly gives a Cv of _.179_.
>
> 60 psi gives you something like 1.5 gpm.
>
> Try calling Rainbirds help line.
>
> -zero
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