# Lawn keeps getting dry areas...



## Michael58 (Aug 16, 2020)

Can you guys see if I'm on the right track here or doing something wrong? I've spent countless hours fine tuning my sprinkler system, adjusting spray patterns, nozzle sizes, measuring with catch cups, etc. yet I still get large areas going blue/grey color and then start to die off. I've been able to hopefully recover most of it by hand watering when I see this, but I really don't want to spend the time hand watering every day or two these areas.

Here's my setup:

Backyard lawn has 4 zones, 3 of which are Hunter PGP ADJ rotors, the last zone is the MP Rotators.
It looks like the MP Rotators do about .4"/hr and my rotors are tuned the best I can for even coverage at about .33"/hr.

The font yard has MP Rotators as well, and still does get some of these dry areas, sometimes even after a day and a half from the last watering.

I water everything 3 times a week, the MP Rotators run 50min and the rotors 72min. To me that means I should be getting a little over an inch on the rotors per week, which I thought was good since we're in April/May, the highs are in the 80's and just getting into the 90's.

From tools online I believe I have "Sandy loam"... should I be watering less and more frequently? I thought that was the wrong thing to do, but it seems like the grass can hardly make it for a couple days without water.


----------



## Mightyquinn (Jan 31, 2017)

Where are these dry areas located at in terms of the arc of the irrigation heads? On they on the very edges or where two heads overlap? What time of day are they going off? Could wind or water pressure be effecting the output of the irrigation heads?

I know my irrigation will spray further early in the morning than if I run it later in the morning when everyone is awake and showering they won't spray as far. Just some things to think about.


----------



## mjh648 (Sep 1, 2020)

Sandy soils does in fact mean more frequent and less volume per watering session. Look at stuff like available water capacity per soil type. Clay can store up to 4X as much water as a sandy soil. Maybe add another day per week and see if that helps.


----------



## g-man (Jun 15, 2017)

Read the ET and irrigation guide at the top of this folder. It will help with some of the calculations. You likely need 1.5in of irrigation right now.

When you setup a catch up in the dry area vs the wet area, how long does it take to get to 0.5in in each of the two areas?


----------



## Michael58 (Aug 16, 2020)

For sandy loam and if I use 6" root depth, I should be watering about .375" each time right? That should be about 67 minutes on the rotors, except for some inefficiencies... but I think my coverage is pretty good. I haven't timed how long to .5" yet, I think that would be about 90 minutes per zone, I've only calculated it out based on shorter run times.

But if my max should be .375" per watering, maybe I do need to add a 4th day per week in there... It doesn't seem like one particular dry area, it seems like large sections start to wilt like I'm underwatering.... My goal is to have it be as drought resistant as possible in our hot climate...

We don't have the best water pressure but it seems alright during the night. We try to finish watering by 6am.

Thanks all!


----------



## g-man (Jun 15, 2017)

Don't calculate the times. Do a catch cup audit of your system. Place the cups (eg. Empty tuna cans) and let the system run for 30min. Measure the irrigation in inches for each cup.


----------



## mjh648 (Sep 1, 2020)

to reiterate @g-man throw some catch cups in the dried out areas and the most lush areas so you know your true efficiency (bottom 3 average divided by total average).

These are pretty useful.

https://www.amazon.com/gp/product/B005C5OP8G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


----------



## SCGrassMan (Dec 17, 2017)

Shoot for 2" a week for a couple weeks, and see how it goes!


----------



## Michael58 (Aug 16, 2020)

Okay, after doing more catch cups I think I still had coverage issues even with all my adjustments. I think the person who installed these Hunter PGP ADJ rotors put some of them too far apart. When I back off the screw to break the stream, I get it watering really heavy on the very end of the stream, and it usually still doesn't reach some of the other heads.

It's still watering, but it is very difficult to get it even as if I break another stream more to compensate for the first sprinkler not reaching it, then it doesn't go as far, and it repeats... It also doesn't help my water pressure I think is around 40psi.

Has anyone had better luck with the Rain Bird 5004 watering more evenly, especially close to the head? Not sure what else to try since I can't get higher water pressure to get more throw...


----------



## Wiley (Dec 2, 2019)

Michael58 said:


> Okay, after doing more catch cups I think I still had coverage issues even with all my adjustments. I think the person who installed these Hunter PGP ADJ rotors put some of them too far apart. When I back off the screw to break the stream, I get it watering really heavy on the very end of the stream, and it usually still doesn't reach some of the other heads.
> 
> It's still watering, but it is very difficult to get it even as if I break another stream more to compensate for the first sprinkler not reaching it, then it doesn't go as far, and it repeats... It also doesn't help my water pressure I think is around 40psi.
> 
> Has anyone had better luck with the Rain Bird 5004 watering more evenly, especially close to the head? Not sure what else to try since I can't get higher water pressure to get more throw...


How far apart are the heads? If your GPM allows you could split the difference between heads and add another sprinkler. On another note, our part of the valley is really dry right now even though temps have not met their apex. If your irrigating about an inch a week your lawn will be looking dry right now. Depending on cost, access and local restrictions I would increase your weekly irrigation if it's in the cards.


----------



## bernstem (Jan 16, 2018)

Rotor heads will look like they are watering all at the end of the spray, and that is normal. Despite appearances, there is still a lot of water in the whole path, but it isn't even coverage. They are designed to completely overlap with the adjacent irrigation head; if you have head to head coverage, then you will get uniform coverage. If you don't have head to head coverage, then you will get dry spots (often right next to the heads) which sounds like what you are seeing with your catch can audit.

Fixing dry spots from excessive spacing can be difficult. The best option is to rework the zone for head to head coverage by adding irrigation heads.


----------



## Michael58 (Aug 16, 2020)

The rotors are about 25-30 ft. apart, last night I changed the nozzles out to match the flow rates per half circle, 90, etc. and I tried to keep the sizing down to get maximum pressure and distance. I think I got head to head coverage now, so that's great, but I was just wondering if these Hunter PGP ADJ are okay to use without breaking the stream at all?


----------



## bernstem (Jan 16, 2018)

Yes, they are designed to work with no distance reduction. You will likely get the best uniformity without using the radius reduction screw and head to head coverage.

https://www.irrigationtutorials.com/sprinkler-coverage-nozzle-selection-sprinkler-spacings/


----------



## g-man (Jun 15, 2017)

@Michael58 Try to draw up your setup with the distance and such. It will help you visualize if there is a head that needs to be moved.

Meanwhile, you might need to overwater some areas to ensure other areas get enough water until you get even distribution.


----------



## Utk03analyst (Jun 8, 2019)

I have Pgp's and my radius is about 45 feet on the large side max heads on a zone of 3 and I flow at 12 gpm's and have the blue 4gpm nozzles in them. I would also look at the nozzle chart and nozzles to match your gpm and desired distance .


----------



## Vtx531 (Jul 1, 2019)

Michael58 said:


> The rotors are about 25-30 ft. apart, last night I changed the nozzles out to match the flow rates per half circle, 90, etc. and I tried to keep the sizing down to get maximum pressure and distance. I think I got head to head coverage now, so that's great, but I was just wondering if these Hunter PGP ADJ are okay to use without breaking the stream at all?


When you say you changed the nozzles out to match flow rate..I'm assuming you mean precip rate? The flow rate needs to be different...ie half circle needs to flow ~2x as much as a 90 degree arc.

They are best to use without breaking the stream. They should look like they are flowing way more water to the outside radius. Same concept as the 180 degree arc being twice as much area as a 90 degree arc and needing more flow rate. As you go further out in radius from the head, the stream needs to cover an exponentially larger area of lawn and needs an exponentially increased precep rate the further the stream goes from the rotor.

As for dry spots, ideally your system would be 100% even coverage but this is not realistic. In the real world, you would water enough to get rid of the dry spots and all the rest would be overwatered.


----------

