Sprinkler Irrigation 123 Tutorial - Calculating Your Zone
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.
YOU HAVE CHOICES! You can now decide how you want to install the system, plumbing it into your water line, or using the hose bib as your connection point. Many Irrigation Contractors will likely insist it’s not viable to install an inground installation from your hose bib, but this isn’t so, and it will likely make more sense for small to medium lawn installations. Installing from a hose bib can be done by either using a multi-port timer, or by connecting the bib to an actual solenoid manifold which would be very similar to actually plumbing the system into your water supply.
Here is a brief Summary of advantages and disadvantages of using Hose End Timers vs. Solenoid Valve Assemblies:
For simplicity sake, we will design our system with a solenoid valve assembly connected to a household hose bib.
When planning your pipe/tube layout it’s best practice to try to minimize run length while also eliminating unnecessary corners and changes of direction. This will minimize pressure loss down the line and improve the flow rate to the heads of your system. We will now look at how to determine zones of your system. As we stated at the start of our tutorial, we are assuming a maximum flow rate of 240 gph and pressure of 60 psi.
Since we have our gph usage from each nozzle and our gph available from our water source we can now plan our zones and tubing layout. The first step is to calculate your zones. We always recommend a zone to not exceed 75% of the water available. We’re going to ignore significant pressure loss, as the distance covered isn’t very significant.
Lets now revisit our water usage for the lawn. We will assume we have about 210 gph of water available (280 gph x 75%). We multiply our water supply by 75% to ensure we are on the safe side of having enough water when calculating our zones. Lets now try to create our first zone.
Let’s start with our First Zone.
Let’s move on to Zone 2.