Adjusting Hunter PGP Throw

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stephensilva1
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Adjusting Hunter PGP Throw

Post by stephensilva1 » August 6th, 2015, 7:51 am

I went out this morning at 5am to check the heads and noticed that the ones in the front yard were throwing further than I measured during the day (I'm assuming higher water pressure).

I was wondering what would be the best way for me to reduce the radius on some of my Hunter PGPs?

The heads in the front yard have a #3 nozzle and at 40 PSI are said to reach 31' with a flow of 1 GPM.

1) Use the radius adjustment screw? (Though I read it messes with coverage)
2) Change to a smaller nozzle (#1 or #2)? Is it ok to reduce the flow even further?
3) Decrease flow to the zone through the valves (Hunter PGV)?

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Re: Adjusting Hunter PGP Throw

Post by rydaddy » August 6th, 2015, 8:15 am

You won't be able to get it perfect. Go to a lower nozzle if it helps with your available GPM. Adjust as necessary.


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Re: Adjusting Hunter PGP Throw

Post by stephensilva1 » August 6th, 2015, 3:05 pm

Well my system has a flow of 11 GPM and the front yard only has the four heads at 1 GPM each so available flow isn't the problem. I was just wondering if people had a bad experience using the radius adjustment screw and getting even coverage?

Going to a smaller nozzle would reduce the radius but wouldn't it also substantially decrease the precipitation rate?

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Re: Adjusting Hunter PGP Throw

Post by Green » August 6th, 2015, 3:08 pm

Yes, just remember that the adjustment screw only changes the distribution, not the flow or amount of water...different nozzles change that. I would only change the nozzle if you have too much or too little water in an area.

Btw, how did you measure your system GPM and your PSI values? I never got a good explanation on how to do it.

Also: anyone know whether the zone valve has to adjusted when you change a nozzle in a head in that zone? This bit of info would be of use to me (and the OP, I think).

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Re: Adjusting Hunter PGP Throw

Post by Kmartel » August 6th, 2015, 8:35 pm

Why not put in larger nozzles so your 4 heads put out 8-9 gpm? Then use screw to adjust radius. At the current rate I would thing your precipitation rates would be terrible.


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Re: Adjusting Hunter PGP Throw

Post by stephensilva1 » August 6th, 2015, 8:44 pm

The front yard is approximately a 29'x29' square, with 4 PGPs in each corner. I installed the #3 nozzle because at 40 PSI it's rated to be about 31' so I'm getting a few feet of overshoot.

Is it common practice to install a larger nozzle and then use the screw to decrease the radius? I was under the impression that you picked the nozzle based on the radius? However, I do like the idea of increasing the precipitation rate by using a larger nozzle.

Hunter recommends using the radius adjustment screw to decrease the radius by no more than 25%.

If I used a #5 nozzle at 40 PSI, it's rated for 36 feet. Decreasing it to about 29' would be less than 25%, so would that work?

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Re: Adjusting Hunter PGP Throw

Post by Kmartel » August 6th, 2015, 9:08 pm

stephensilva1 wrote:The front yard is approximately a 29'x29' square, with 4 PGPs in each corner. I installed the #3 nozzle because at 40 PSI it's rated to be about 31' so I'm getting a few feet of overshoot.

Is it common practice to install a larger nozzle and then use the screw to decrease the radius? I was under the impression that you picked the nozzle based on the radius? However, I do like the idea of increasing the precipitation rate by using a larger nozzle.

Hunter recommends using the radius adjustment screw to decrease the radius by no more than 25%.

If I used a #5 nozzle at 40 PSI, it's rated for 36 feet. Decreasing it to about 29' would be less than 25%, so would that work?
If you already own the nozzles then it can't hurt to try. Your at 20% reduction according to the info you provide.


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Re: Adjusting Hunter PGP Throw

Post by Green » August 6th, 2015, 11:26 pm

You can do whatever works. Don't always have to follow the rules. I'm new to in-ground sprinklers, but I already can tell I like the radius adjustment screw, because it makes more of a curtain effect when it's used even just slightly. Only negative I can think of, was someone posted on here in the past about it accumulating debris and then becoming hard to turn.

Also, the manufacturer stated radius numbers are probably optimistic. Another reason not to max out the distance with a given nozzle.

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Re: Adjusting Hunter PGP Throw

Post by stephensilva1 » August 7th, 2015, 8:52 am

Ok sounds good, I'll give it a try then!

Also forgot to include in my last reply that I read and followed the tutorial on designing a sprinkler system at irrigationtutorials.com

I highly recommend reading it even if you don't have to install one yourself. He explains a lot about sprinkler systems and how to easily calculate psi and gpm. Off the top of my head the flow was calculated using the size of your water meter, the supply pipe size and maybe a few other things. Try here: http://www.irrigationtutorials.com/gpm- ... er-source/

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Re: Adjusting Hunter PGP Throw

Post by rydaddy » August 7th, 2015, 9:51 am

Ignore the radius on Hunters charts. Go with what you need for GPM and adjust accordingly. It will not be perfect. 1.0 is really low. 2.5 and bigger is a better starting point.


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Re: Adjusting Hunter PGP Throw

Post by BoatDrinksQ5 » August 7th, 2015, 9:56 am

I find that you get the best water distribution when the screw just touches the water stream a touch. once you really start reducing the distance and interupting the stream it makes for more less even of a curtain. more of a spray.

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Re: Adjusting Hunter PGP Throw

Post by Green » August 7th, 2015, 3:42 pm

BoatDrinksQ5 wrote:I find that you get the best water distribution when the screw just touches the water stream a touch. once you really start reducing the distance and interupting the stream it makes for more less even of a curtain. more of a spray.
Yeah, and that's one of the selling points...it can mimic a spray head in tight areas.

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Re: Adjusting Hunter PGP Throw

Post by BoatDrinksQ5 » August 7th, 2015, 4:02 pm

What I have found those is that in tight spaces - if you crank it down past 30%... it actually stops spraying near the head... and only shoots a spray-beam (of droplets...not the typical squirt with curtain). Found I get better watering in tight spaces(side yard) with it adjusted just slightly into the beam - with a lower number nozzle.

It overshoots pretty good into neighbors yard...but gives a good even watering on my lawn throughout the range of the arc.

kind of hard to explain...

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Re: Adjusting Hunter PGP Throw

Post by stephensilva1 » August 10th, 2015, 6:19 am

Ok so I went out this morning and swapped the #3 nozzles on the front PGPs with #6 (36' and 2.4 gpm @ 40 PSI). The 4 heads add up to 9.6 gpm, which works out great for my total available flow (11 gpm).

I had a question about my PGP heads in the back yard. The four of them are also #6 nozzles, but I was wondering if I could either increase them all to #7? At 3.0 gpm each, they would exceed my total available flow by 1. What would happen if that were to happen?

If that was a problem, is it possible to switch 1 or 2 of the heads to #7 nozzles, while keeping the rest as #6 as long as they didn't add up to more than 11 gpm?

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Re: Adjusting Hunter PGP Throw

Post by BoatDrinksQ5 » August 10th, 2015, 1:11 pm

If you raise nozzles to above total flow your pressure and performance out of the heads would fall from spec.

They still might provide acceptable results, would need to try.

I have higher and lower nozzles on the same zone - allows for adjustment for sun/soil conditions. Also accounts for areas of varying overlap, quarter turn vs full turn heads..etc.

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Re: Adjusting Hunter PGP Throw

Post by ENVY23 » August 10th, 2015, 3:03 pm

You may already know this, but you need to pay attention to the arc of your heads. You can't just go around switching out nozzles. A head with a 90* arc needs a nozzle that is half the size of a head with a 180* arc. For example if you have a 180* head with a 5gpm nozzle, the 90* head would need to be a 2.5gpm nozzle, because the 90* head will make twice as many passes over it's area than the 180* head would make during the same time frame. If both have the same size nozzle, the area the 90* head covers would be overwatered, or the area the 180* head covers would be under watered. In either account you wouldn't be receiving even coverage. A good example would be the second hand on a clock. In 30 seconds the 90* head would go from 12 to 3(15 secs) then from 3 back to 12, 2 passes. During that same 30 secs, the 180* head would go from 12 to 6 and only make one pass. Again, this may be something you already know, but I just thought it was worth pointing out.

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Re: Adjusting Hunter PGP Throw

Post by Green » August 10th, 2015, 7:21 pm

If you exceed the max limit, you could have plumbing issues potentially, according to irrigation tutorials. It will wear the pipes in your plumbing out faster, and/or cause water hammer when shutting off or turning on. I wonder if turning on the water faucet full blast does the same. I commonly do that.

The thing about coverage falling off further from the head is easy to test with containers. I was surprised when I got very little water at the limit of the spray distance. It's weird, but you have to set the heads to shoot past what you're watering sometimes. This can be an issue with neighbors who always water in the evening...if their stream overlaps your yard, and you get lawn disease from that...just enough to get the blades wet before night.

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Re: Adjusting Hunter PGP Throw

Post by stephensilva1 » August 10th, 2015, 7:25 pm

Yep I read that concept on irrigationtutorials, but it's definitely worth repeating.

All of my PGPs are at the corners of a square, so they're set at 90* arcs. I increased the nozzles on 2 of the heads that are sunnier, so that the total flow was within my system's limit and for now it seems to work well.

It really shouldn't matter for the next month since I'll be lightly watering the reno, but I'll definitely have to measure the precipitation rate throughout the lawn to make sure I don't end up under/over-watering certain spots in the future.

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Re: Adjusting Hunter PGP Throw

Post by Green » August 10th, 2015, 7:27 pm

ENVY23 wrote:You may already know this, but you need to pay attention to the arc of your heads. You can't just go around switching out nozzles. A head with a 90* arc needs a nozzle that is half the size of a head with a 180* arc. For example if you have a 180* head with a 5gpm nozzle, the 90* head would need to be a 2.5gpm nozzle, because the 90* head will make twice as many passes over it's area than the 180* head would make during the same time frame. If both have the same size nozzle, the area the 90* head covers would be overwatered, or the area the 180* head covers would be under watered. In either account you wouldn't be receiving even coverage. A good example would be the second hand on a clock. In 30 seconds the 90* head would go from 12 to 3(15 secs) then from 3 back to 12, 2 passes. During that same 30 secs, the 180* head would go from 12 to 6 and only make one pass. Again, this may be something you already know, but I just thought it was worth pointing out.

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Very true. It's at least a starting point. But you may still have to switch out a nozzle or two to get it right.

Also I'll add that low-angle heads have a higher precipitation rate than a standard nozzle with the same gpm because the water is kept closer to the ground and doesn't arc upward as much. I believe it's really the precipitation rate, not so much the flow rate in gpm, that matters. Often, situations where low-angle nozzles are useful call for both the lower angle and higher precipitation rate.

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Re: Adjusting Hunter PGP Throw

Post by Green » August 10th, 2015, 7:29 pm

stephensilva1 wrote:Yep I read that concept on irrigationtutorials, but it's definitely worth repeating.

All of my PGPs are at the corners of a square, so they're set at 90* arcs. I increased the nozzles on 2 of the heads that are sunnier, so that the total flow was within my system's limit and for now it seems to work well.

It really shouldn't matter for the next month since I'll be lightly watering the reno, but I'll definitely have to measure the precipitation rate throughout the lawn to make sure I don't end up under/over-watering certain spots in the future.
Yeah, I'm testing precipitation rate on my newly installed system lately. It wasn't evenly watering right after the install, so I'm using a guess-and-check method to get the right nozzles in each head, making sure to keep the total under 12.5 gpm or so (due to the type of pipe I have).

You could start with just 5 containers...one for each corner and a middle one.

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