# Increased Nozzle Size Increases Spray Distance?



## shiltz (Aug 14, 2020)

Hoping someone can explain this to me. I am in the process of increasing the Nozzle sizes of my Rainbird 5000 sprinklers. When reading the chart is shows that increasing the nozzle size for a certain PSI increases the spray radius. Can someone explain this? I assumed that smaller nozzles would have more PSI and shoot a further distance. Thank you!


----------



## Grizzly Adam (May 5, 2017)

The larger the nozzle number the less restriction there is on the water flow. The decrease in restriction allows it to squirt further. This might be counter-intuitive, but remember that even the larger numbers are by definition "nozzles" and not just unregulated openings. The slightly larger holes from a #1 nozzle to a #6 is not enough to significantly drop the pressure that the nozzle is outputting at, but there is less resistance which allows the water to go slightly further. There is a breaking point, however, as you can see on the chart where some of the very large nozzles are then spraying less far as they are operating at less pressure.


----------



## shiltz (Aug 14, 2020)

Grizzly Adam said:


> The larger the nozzle number the less restriction there is on the water flow. The decrease in restriction allows it to squirt further. This might be counter-intuitive, but remember that even the larger numbers are by definition "nozzles" and not just unregulated openings. The slightly larger holes from a #1 nozzle to a #6 is not enough to significantly drop the pressure that the nozzle is outputting at, but there is less resistance which allows the water to go slightly further. There is a breaking point, however, as you can see on the chart where some of the very large nozzles are then spraying less far as they are operating at less pressure.


Thank you for the response! Makes sense now.


----------



## MasterMech (Sep 24, 2017)

Pressure at the nozzle determines the velocity of the water stream leaving the nozzle.

Increasing the nozzle flow rate means increasing the mass of the water stream.

More mass (at the same velocity) = more inertia. Heavy streams "coast" further out from the head as they retain energy longer.

The ratio of stream mass to surface area also improves, favoring less aerodynamic drag for a given stream mass. Two 2.5 GPM streams will not travel as far as one 5 gpm stream given the same pressure available at the nozzle.

At some point, the increase in flow will reduce the PSI available at the nozzle as the supply limit is approached. Further increasing the nozzle opening may increase the distance travelled by the stream, but the loss in pressure will start to quickly overcome any gains from the heavier and more aerodynamic stream.

Larger streams are also more resistant to wind deflection. Note that many of the smaller nozzles are available in a "low angle" version to combat wind deflection of the stream.


----------



## shiltz (Aug 14, 2020)

MasterMech said:


> Pressure at the nozzle determines the velocity of the water stream leaving the nozzle.
> 
> Increasing the nozzle flow rate means increasing the mass of the water stream.
> 
> ...


Thanks for the info! We replaced the motor on our well pump and Im trying to adjust the nozzles to fit our system . Thanks for taking the time to write such a good explanation.


----------



## The Lawnfather (May 2, 2020)

I just started trying this yesterday, I was having problems with coverage in the middle of my sprinklers. I started where stress was evident, and where sprinklers were doing a 180 leaving the 90 on the end of my zone with the smaller nozzle. Make sense to me that sprinklers covering a large area should have larger nozzle to put down the same water. In most cases it did increase distance while allowing to to throw water "fuzzy" and not a stream. I would start where stress is evident


----------



## penright (Apr 6, 2020)

If I understand what @MasterMech said, as you increase the size and you reach max flow, then pressure drops. Just like @The Lawnfather l I had uneven coverage.
I have 9 5004. 4 90's, 4 180's, and 1 360. Digging into it all heads had the same 2.5. I am guessing the guy who installed just left the default nozzles in. 
My question is, how do you do the math to know when you are reaching "max flow"?
I have measured my water at 5 GPM (through a 100' 3/4" hose). I have 50 psi.
So I have nine 2.5, assuming I am not hitting max flow, then the total nozzle flow would be 22.5 GPM?

My main line is 1" connected just a few feet from the meter, so its performance will be better than what I measured, but that much?

What am I missing?

Little off the thread topic, the reason I want to understand is so I can better balance my nozzles. If I use a 1.0 for the 90's, a 2.0 for the 180's, and 4 for the 360, if I add them up I would be at 16 GPM. That is less than 22.5, but all this assumes the math that I am doing, which may not be correct.


----------



## g-man (Jun 15, 2017)

Your math looks correct and the head layout looks correct. You add all the heads in a zone with their rated numbers from the charts the vendors provide. Switching to a 4:2:1 ratio is also the correct way to get even distribution.

Next the max SAFE gpm is a function of the pipe diameter/type. This website is a great resource that keeps crashing. The web archive is a good backup. https://web.archive.org/web/20190125104935/https://www.irrigationtutorials.com/

For 1in copper line, the SAFE gpm is 18gpm. https://web.archive.org/web/20200919001341/https://www.irrigationtutorials.com/gpm-psi-municipal-water-source/
Avoid having a zone with a design gpm greater than 18gpm.


----------



## MasterMech (Sep 24, 2017)

@penright If you need to know for certain exactly what your flow is, you can measure nozzle pressure with one of these, and then consult a flow chart for your sprinkler head. Should list GPM for a given pressure with any specific nozzle size.


----------



## Monocot Master (Feb 28, 2021)

If anyone is not on to these yet, the 5000 Series MPR Nozzles are excellent. At least for head spacing of 35' or less. Adjusting the radius screw on rotors makes matching rates a guessing game. Read the specs and literature and you will see what I mean about the advantage of using these nozzles.

https://www.rainbird.com/products/5000-series-mpr-nozzles


----------

