# Why regulate at 40 PSI - Hunter Pro Spray



## Thick n Dense (May 7, 2019)

I'm adding a couple of heads to existing zones and trying to figure out why it would be beneficial to use the spray bodies that regulate the psi at 40?

Is this only beneficial in a low psi system? or can someone with 80 psi benefit last well?

Debating if i should spend the extra money on it, any help would be appreciated.


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## Green (Dec 24, 2017)

Thick n Dense said:


> I'm adding a couple of heads to existing zones and trying to figure out why it would be beneficial to use the spray bodies that regulate the psi at 40?
> 
> Is this only beneficial in a low psi system? or can someone with 80 psi benefit last well?
> 
> Debating if i should spend the extra money on it, any help would be appreciated.


It has to do with how sprinklers work. When the water moves too fast, it tends to cause a lot of small drops. The mist is not efficient at watering.

They say 45 psi is ideal for the rotary heads, and 30 psi for sprays, and 40 for multi-stream rotary nozzles installed in spray bodies.

You can buy the pressure regulated sprinkler bodies in both styles (PRB rotors and PRS sprays), or you can buy an accessory regulator that fits under the rotor body, called the PR-075.

If you have static psi over, say, 60, you'd actually benefit from these regulated sprinklers the most.

Pressure compensating devices are something different. They're for when your psi is already in the right ballpark, but maybe fluctuates during operation, or is a tad higher than it should be. They're basically washers inside the screen that fits under the spray nozzle. Rainbird makes a line of them.


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## Thick n Dense (May 7, 2019)

Thanks for the response.

So I have a high psi at 80ish but most of my zones in my design are large and will need many heads.... however the front strip will only have 5 heads, is it safe to say that I would only benefit on the zone with 5 heads and the zones with 10-15 heads will distribute the pressure more evenly ?


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## Ware (Jan 28, 2017)

Thick n Dense said:


> I'm adding a couple of heads to existing zones and trying to figure out why it would be beneficial to use the spray bodies that regulate the psi at 40?
> 
> Is this only beneficial in a low psi system? or can someone with 80 psi benefit last well?
> 
> Debating if i should spend the extra money on it, any help would be appreciated.


I would say the opposite - the pressure regulated spray bodies would be even more beneficial on a system with higher pressures. Regulating all the spray bodies down to 40psi will optimize the performance of each nozzle and also provide more uniform distribution because all the heads will be operating at the same pressure.


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## Green (Dec 24, 2017)

@Thick n Dense what Ware said.

At the same time though, the more heads you have and the longer the piping, the more pressure drop you'll tend to have on average. I'm not an expert in either sprinklers or physics, but these are basics that you'll keep encountering over and over. How many heads does it take to drop the pressure? I guess you'd have to measure it at each head to know. Most people won't do that, I think.


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## TSGarp007 (May 22, 2018)

How did you measure your static psi? Try measuring that pressure separately while each zone is running.


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## Thick n Dense (May 7, 2019)

Theres a spigot on my system before the BFP. 
This is a good idea, I can check that pressure when the zone is on to see if the heads deop enough to fall into the good range ~40 psi. I can almost guarantee that the zone with only 5 heads and 2 of which are 90's are running at way higher pressure.


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## Thick n Dense (May 7, 2019)

Another question, is there any real difference between an inline regulator and regulators within the spray body ?

I would think that with the inline regulator, if pressure loss occurs for various reasons the regulator would drop below 40 psi then correct it self back up... Is this correct?


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