# Lots of questions for a new design



## Daugela (Nov 24, 2019)

Hello everyone. I'm a longtime DIYer who just found this forum. I'm normally on another popular DIY forum but it seems this is the place to be for lawn care, etc.

I've tried searching my topic but couldn't find anything specific. While I have many questions, I will try to make this simple.

I'm designing my own sprinkler system in Phoenix, AZ. Attached is a worksheet that was made by a free online source. Indicates there will be 5 zones. I will have 1 zone for drip system. The rest are for the lawn.

Service: 3/4" PVC
8.1 GPM MAX
63 PSI

According to this print out, despite having a 3/4" service, several of the pipes from the manifold to the heads require 1" pipe. Can someone explain why this is? More volume for the heads/GPM?

It also calls for 2 manifold boxes. Is that normal for a 5 zone system? Or is one large one better? I know the large boxes are extremely expensive.

If you look at my design, I'm not sure what ZONE 1 is for. I didn't include ZONE 5 because it's for the drip system.


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## corneliani (Apr 2, 2019)

A few questions: 
- What is the scale of the drawing? That helps set some reference. 
- What is in the bottom-right corner of the drawing that's requiring all those heads placed around it?

As for the reason 1" pipe is used even though the service is only 3/4"... generally the larger a pipe's diameter the less friction and the lower velocity.


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## Daugela (Nov 24, 2019)

What is the scale of the drawing? That helps set some reference.

This might be hard to explain. Do you see the two black lines on both sides of the sidewalk? Each is 10 feet. The black line in the very front of the house (all black lines) is a 2' wall. I have a raised front yard.

What is in the bottom-right corner of the drawing that's requiring all those heads placed around it?

The front wall on the bottom right corner goes around a fire hydrant.


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## Ge0rdi3brit (Aug 30, 2018)

The size of pipe required is based on many factors, such as the volume of water you have available at the beginning of the valve, and the distance the water has to travel to get to the heads. Every turn in the pipe reduces the pressure a little as well. This dictates how many heads you can have in each zone.
It looks like you just have four zones, including your drip zone. The additional valve is likely being used as a master valve. 
Perhaps I don't understand what's being displayed in the hexagons, but I find it odd that zones two and three only have three sprinkler heads, while zone four has seven. 
I wouldn't put more than four valves in a single valve box as more than that would make it difficult to service what's in there.


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## corneliani (Apr 2, 2019)

I took a few minutes to print out your drawing and do a quick sketch of a possible layout, for reference. I honestly recommend that you read through the design tutorial at https://www.irrigationtutorials.com/landscape-sprinkler-system-design-tutorial/. It has all the relevant info (and more!) that can turn you into a pro.

(The placement of the manifold box will depend on your site conditions)

The logic behind my design is: use 1 zone for the small portion on the other side of the sidewalk by using low-flow Rotators, especially since the throw is 15-16'. Rotors like to shoot farther distances than that, and sprays are very inefficient and use high water flow (I think that's what the current design has in mind, hence requiring 2 zones for ~450sqft). If you go with something like the Hunter MP2000s you'll need *2.6-gpm to push all 6 heads* as I laid out.

For the main yard portion you can either go with long-throw Rotors (I spec'd the PGP Ultra's simply because the spec book is on my desk) or you can choose to continue with Rotators and space them at approx 18'. The smaller throw Rotors will give you more precision but likewise more heads. The longer throw Rotors cover more area but may not have ideal placement.

PS: I noticed after uploading my sketch that the the 38' radius heads require a total of 9 GPM if grouped on one zone, as they should be. I think you maxed out at 8.x-gpm so this won't work exactly... but i'm just giving you a reference for how things should be done and not a 100% design. You really need to tweak it to your site conditions (slope/topography, soil characteristics, length of pipe runs and subsequent pipe friction loss, etc).

Hope this helps.


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## Daugela (Nov 24, 2019)

I appreciate all the quick replies. I went to my local sprinkler/irrigation store (not box store) and they were perplexed as to why my plans called for the lines to be enlarged from 3/4" (service) to 1" from the manifold. The plans also call for the 1" line to be reduced back to 3/4" just before the heads. They guys at the store said it would be pointless to do that. Simply keep it 3/4".

Corneliani - Thank you for drawing it out. It makes more sense to do your version in the small area. My plans call for the Saturn IV heads in the small area and Voyager II in the larger area. As you noted I only have 8 GPM to play with. I re-configured some stuff on the plans to see if the computer would spit out the same thing, etc....I basically added grass along the driveway and removed the paver walkway next to it.

It pumped out 3 zones.

Orange - Drip system
Red - 8 heads - Saturn IV
Blue - 7 heads - Voyager II

As you mentioned will I have enough GPM? Some of the heads I think are overkill. If you look at the small area and large area, there two spots where there are two heads really close to each other. They are there to fill in 100% coverage near the small 90 degree angle portions of the yard. I think I could do away with those. The numbers on the last pic reflect the GPM per head (next to each head).


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## corneliani (Apr 2, 2019)

@Daugela the program really seems to get those corner cutouts all wrong, in a computerized attempt at perfect coverage. That's where I say site conditions dictate the outcome.. if you can spray onto those corner cutouts then treat it like a turf area (remove them from the design, basically). That added head does you nothing but harm by doubling the water where you now have double coverage compared to the other heads. Also if you have a slope down towards the front then you can feel comfortable that the bottom-right head, even though it's not in line with the sidewalk/retaining wall, will allow for water to flow down grade into that missed area. In the meantime the other heads will give you the other half of the required water.


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