# Help with sprinkler system layout



## sambisu (Apr 15, 2020)

Hi all - I am trying to design an in-ground irrigation system for our yard and could use a little assistance. We have some odd shaped areas that I am having trouble figuring out the right combinations of sprinkler heads to cover.

One area that was giving me trouble in particular is the small lawn area in the bottom right of the drawing below. That little area at the top is 6' x 6'. I was looking at Rain Bird HE-VAN nozzles (maybe there is something better for my application) and it looked like the only way to get down to a 6' spray radius was to reduce the pressure down to 20 psi. I was planning on regulating the whole system down to 30 psi. Not sure if I can stick in line pressure regulators in to run just certain sprinklers at a lower pressure?

Any help would be much appreciated!


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## TSGarp007 (May 22, 2018)

I wouldn't reduce the pressure (to 30) for the regular sprinklers. I think the hunter MP rotators corner version would work for that small corner.


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## sambisu (Apr 15, 2020)

It looks like the Hunters need to be operated at 30 psi to get down to the 6 ft radius. Which will be easier to work with than the Rain Birds that needed to be at 20 psi for a 6 ft radius. So the Hunters may work better for me. Thanks!


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## TSGarp007 (May 22, 2018)

I was thinking the corner and strip nozzles which max out at 6' with 50 psi if I remember correctly. But yeah they have the regular kind that can get that low at 30. But I wouldn't reduce pressure down to 30 psi prior to an entire zone. I would just use a pressure regulating spray body when necessary (e.g. Hunter PRS30). I'd preserve my water pressure to help move the gpm through the pipes. Not sure exactly what your overall plan is though, for very low gpm zones the low pressure could work. Some math would answer any doubt...


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## sambisu (Apr 15, 2020)

Looks like the Hunters call for 40 psi - is that what you would normally run a zone at? Weird that the Rain Birds recommend 30 psi. Is there a general consensus about which brand is best?


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## sambisu (Apr 15, 2020)

What seems appealing to me about the Rain Bird stuff is that they have nozzles that are fully adjustable between 0 and 360 degrees. Which would make it easier to deal with my weird angles. But those nozzles recommend 30 psi.


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## TSGarp007 (May 22, 2018)

It's not a big deal which brand you go with. I've read a lot of people recommending Hunter rotators but I used some rainbirds recently and they're great for me.

Sprinklers also have a max PSI. True they are more efficient at a mid level PSI. However if you set your PSI to 30 out of the valve box, then 100' and 5 sprinklers later it might be 15 (or something). That's why they sell the pressure regulating bodies, so you can have some zone that starts at 50 PSI (for example) and by the last sprinkler at the very end it's only 30. But the pressure regulating spray bodies make each sprinkler behave the same.


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## TSGarp007 (May 22, 2018)

I checked and from what I saw online, the rainbird pressure regulating spray bodies can handle up to 70 psi. The hunter ones up to 100. So both should work for you without reducing your zone pressure, but the hunter ones with more margin for error. You could reduce your pressure some but I wouldn't go as low as 30 for a spray or rotor zone. That's more for drip irrigation... Lots of people on here with more experience than me, hopefully they chime in if I'm misstating anything.


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## jht3 (Jul 27, 2018)

I always add a foot or so to each head overlap, to account for wind, pressure drops, etc

With a normal 8' head you'll probably be fine


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## sambisu (Apr 15, 2020)

Learning as I go here - didn't realize each head had its only pressure regulator. I may be making this more complicated than it needs to be, but this is what I have come up with for spray patterns for the front yard.


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## sambisu (Apr 15, 2020)

I also tried the online Orbit designer thing. Seems like it created an excessive number of zones. The picture I posted above is our front yard and only totals about 12 gpm so should be doable as only one or two zones.


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## sambisu (Apr 15, 2020)

And here is what I came up with for another zone (may need to split into two zones - haven't calculated the gpm yet). Again the Orbit design splits this into 4 zones which seems excessive, but it also does the geometry differently. Thoughts?


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## TSGarp007 (May 22, 2018)

Nice, what are you using, AUTOCAD?

Only some sprinkler bodies come with pressure regulating valves built in. I didn't use them, but in theory they should help evenly distribute your water. Considering you water pressure is around 70 psi you should either use those, or regulate the whole system down some, or both. I just don't recommend reducing your whole system down to 30 psi since you will get some pressure loss from your valve box to your sprinklers. I would reduce it down to the max operating PSI (or just under) for the sprinklers you choose. Then make sure each sprinkler gets a PSI within it's normal operating range. This depends on your sprinkler choice, could vary by zone, and you'll have to do some math based on your initial PSI, gpm per zone and pipe selection. You are right to question the zones. Just need to keep you gpm under your max and water velocity under 5 fps, as well as manage to get precipitation rates around the same for all the sprinklers in your zone (or be willing to have a small area or too end up getting too much water).

Like jht3 said, make sure each sprinkler is capable of at least a foot of overlap. If you are right on the max radius of a sprinkler, consider upgrading to the next larger radius nozzle, just in case you don't get quite as advertised.

I agree I think you could probably use less zones than Orbit recommended, assuming your sprinkler and nozzle choices allow you to come close in matching precipitation rates. I noticed your design for what I think is the back yard has a couple sprinklers in the middle. Looks like the orbit design tried to avoid that. For head to head coverage the sprinkler in the middle is a good thing. I chose against it in my yards just because I don't like sprinklers in the middle of the yard. So that was my reason for going against what I think would normally be recommended. As a result the overlap in the middle part for me is significant (gets up to twice as much water), kind of like your orbit design, it has a small area getting spray from something like 5 sprinklers in the middle. As long as the middle of your yard drains well then it's not a problem, just not as efficient.

Your well on your way. I geeked out with sprinkler placement like this for quite some time before I started buying stuff. I would choose some sprinkler types and nozzles and try and get a relatively even precipitation rate at every spot. You actually can mix rotors with sprays and rotators, but you need to do the math to see if you are actually getting matched precipitation rates. Companies started advertising that some of their nozzles for things like rotators have matched precipitation for their rotators. You can choose a spot in your yard and check how much water it is getting from each sprinkler to determine the precip rate. I went a little nerdy and had an excel spreadsheet with the flow rate for each sprinkler nozzle, the desired radius of that sprinkler, the calculated precip rate from that sprinkler. Then that made it easy for me to choose a spot in the yard and add up the precip rates from each sprinkler that covers it. I'm sure the online design tools are doing something like this for you. Then you can pick which sprinklers are on what zone based on gpm limitations, location, and precipitation rates. A little too much precip rate in an area is OK (assuming good drainage), just inefficient. An area with too little is the problem. You may end up watering the majority of the zone to 1 inch just to get 0.1 inch in your dry spot. That's the real thing to avoid.

Then you can start designing your pipes, using the gpm from each sprinkler to feed into the gpm per pipe. I calculated the psi drop and fluid velocity for each section of pipe. You can calculate the pressure loss from your supply all the way to each sprinkler to find out the estimated pressure at the sprinkler. irrigationtutorials.com covers that of course. But everything the water flows through can cause a pressure drop, as well as elevation change - backflow preventers, valves, elbows, etc... There are online calculators for pressure loss through pipes such as PVC. Manufacturers also publish pressure loss tables with pressure loss based on pipe size and gpm per every 100 feet of pipe. Anywhere the velocity or PSI loss is too high, just upgrade the size of the pipe. When in doubt, increase the diameter of pipe. You need to have enough pressure at each sprinkler, that's why I wouldn't reduce the overall pressure to 30 psi. Your drip zones will probably need to be reduced at some point since your 70 psi is too high for most drip irrigation. You may want to reduce your initial pressure to something a little less than your 70 PSI. Really all that matters is the PSI is in the operating range of all your equipment. Mine is around 55 PSI so I didn't need to reduce it. I'm sure others on here have reduced their overall pressure, and it's very common to reduce the pressure for drip irrigation zones.

I'm not an expert, just a DIY'er that just did a large project myself the way I described. I already understood pressure loss concepts, and you may also, but really anyone can figure it out since you can use online calculators and look up tables. No bernoulli's equations required... irrigationtutorials.com has lots of info if you haven't read it yet.


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## sambisu (Apr 15, 2020)

Yep...AutoCAD (luckily I have it for work already).

This is sort of a fun design challenge - getting the precip rates as even as possible. My target has been to 2-4 sprinklers overlapping in any given spot - which I think I generally accomplished. There are a few very small spots with 5 or 1. I'm using all Rain Bird matched precip rate nozzles with pressure regulating bodies.

My plan for water pressure is to run the full 70-80 psi from the house out to first valve box and then regulate down to 60-65 psi for the system. I didn't do full pressure loss calculations beyond just looking at the tables and seeing that for 3/4" poly you can go up to about 8 gpm before worrying too much (at least with the length of runs I have) and up to about 14 gpm with 1". So I'm running 1" for the longer supply main (which is still less than 100 ft). I figure with a starting pressure of 60 psi I shouldn't have any issues getting at least 30 at every head.


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## TSGarp007 (May 22, 2018)

Yeah I may have gone overboard on the calculations... Also, maybe some OCD kicked in. I would at least identify the longest run and estimate it's pressure as a sanity check.


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## sambisu (Apr 15, 2020)

Yea I did sort of a worst case scenario pressure calculation today (and to assure myself I could do all the zone distribution tubing in 3/4"). Looks like there should be plenty of pressure.


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