Calculating Zones For a DIY Sprinkler Systems

Step 2. Calculating Your Zones and Tubing Layout

Now that you have your water requirement for the front yard you are ready to calculate your zones and tubing layout.  

Calculating Zones For A Sprinkler System.

The first step in calculating your zones is to determine your overall water requirements in relation to your available water supply.  As we mentioned at the start of our tutorial, we have assumed water supply available of 280 gph at 60 psi.  We recommend planning out your zones with some wiggle room by utilizing only 75% of your actual water supply that is available. So we will assume an available flow of 210 gph (280 gph x 75%).  This maximum amount of water is available to every zone because the zones operate independently. 

Let's now review our total required flow from the nozzle selections we made in the previous segment.

Generally, when you are planning out your zones you group together the spray heads that are in the same location and then calculate whether they can all fit into the same zone. If you do not have the necessary water available to run all of those heads then you have to decide which heads to remove from that grouping/zone. 

Let's create Zone 1.

For Zone 1, we will start with the far corner of the system and take a logical path back to the water source.   Nozzle GPM GPH 1 RN200-ADJ 0.41 24.6 4 RN200-ADJ 0.41 24.6 6 MP800SR-90 0.16 9.60 7 MP800SR-90 0.37 22.2 8 MP800SR-90 0.37 22.2 9 MP800SR-90 0.37 22.2 Total Water Requirements 2.46 147.60   Our total water usage for this zone is calculated at 148 gph, which is comfortably within our available water use (280 GPH). Sure, we could have looked at adding another nozzle, but we always recommend taking the conservative approach when dealing with zoning. Zone 1 is done!!

Let’s move on to Zone 2.

For Zone 2, we have the nozzles with large spray radius and higher output which means we will have fewer nozzles on the zone.   Nozzle GPM GPH 2 RN300-ADJ 0.90 54.0 3 RN300-ADJ 1.60 96.0 5 RN200-ADJ 0.83 49.8 Total Water Requirements 3.33 199.80   The 200 gph requirement is considerably higher than zone 1 but still well within our conservative calculation of water availability.

Finally, we can finish Zone 3.  While Zone 2 brought us close to our maximum water availability Zone 3 will be smaller consisting of just the 3 Strip Nozzles.

The three Strip Nozzles will consume coniderably less water but will give you the option of adding another nozzle down the road if there is a need such as a dry spot in the system. Nozzle GPM GPH 10 RNS-LES-515 0.35 21.0 11 RNS-SS-530 0.60 36.0 12 RNS-RES-515 0.35 21.0 Total Water Requirements 1.3 78

Front Garden

We now have our 3 sprinkler zones, but as you can see, we also have a garden to attend to. There are 2 ways to approach the garden, using Drip Irrigation, or additional Sprinkler Heads, and we will briefly look at both.

Method 1: Using Drip Irrigation with Drip Emitter Tubing (Soaker Hose).

Using Drip Irrigation to water the garden will require another zone referred to as a Drip Zone. Drip Zones are very simple and are usually distinguished by a filter and pressure regulator at the start of the zone/valve. They are inexpensive, easy to install and are vital to the longevity of your system. There are several methods you can use to install a Drip System but here we will focus on the easiest and one of the more commonly used methods, being Drip Emitter Tubing (you will often see this installed in garden beds at commercial buildings and shopping malls). Using this method involves simply running a line from your solenoid assembly to the garden and then branching off emitter tubing throughout the garden bed. We will detail the parts breakdown in our parts summary later in this tutorial.

Method 2: Using MP Rotators.  

If we choose to use MP Rotators for the garden zone, we will likely reconfigure (and as you can see simplify) the sprinkler head layout to cover the garden zone. Would it do as good of a job as drip irrigation and have the benefits of root zone coverage (likely not), but it’s better than hand watering, and you can always add a drip zone later if you’re really not happy with the result. 

If we reconfigure as per the diagram below our new TOTAL flow rate calcuation would be as follows:

As you can see with this alternate configuration we can split the system into two zones rather than the 3 in our initial layout. Zone 1 (Nozzles 1,3,4, and 5) Nozzle GPM GPH 1 RN200-ADJ 0.41 24.6 3 RN300-ADJ 1.60 96.0 4 RN200-ADJ 0.41 24.6 5 RN300-ADJ 0.90 54.0 Total Water Requirements 3.32 199.20   Zone 2 (Nozzles 2,6,7, and 8) Nozzle GPM GPH 2 RN300-ADJ 0.90 54.0 6 RN300-ADJ 0.90 54.0 7 RNS-LES-515 0.35 21.0 8 RNS-SS-530 0.60 36.0 9 RNS-RES-515 0.35 21.0 Total Water Requirements 3.1 186.00

Now that we've estabilshed our Zones for our examples we can now move on to the Tubing Layout for our examples.   

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