Sprinkler Irrigation 123 Tutorial - Calculating Your Zone

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:

 

 

HOSE END TIMER

VALVE ASSEMBLY

Connection

Hose Bib

Hose Bib or Supply Line

Flow Rate

Lower flow rate due to hose bib restrictions

Higher flow rate if plumbed into residential supply line

Zoning Ability

Maximum 4 Zones Per Timer

Unlimited

Expansion

Only with additional timers

Simply add another solenoid

Maintenance

If one zone fails, a new timer is required.

Easy maintenance of individual solenoids

Cost

Although the cost of a hose end timer is lower, the cost of solenoid and controller assembly is greatly reduced as more valves are added. 

 

For simplicity sake, we will design our system with a solenoid valve assembly connected to a household hose bib.

Tubing Layout

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.

 

 

When planning your zones, it’s common practice to create zones based on the area of the lawn you are looking at. We are going to start with front right corner. Determining how many nozzles can go on one zone is simply a matter of adding up the nozzles you have selected and determining how many can be supported with your water source. We have chosen nozzles 1,3,4,5,6, and 7.

  1. MP2000-90 - 25.8 gph (90 degrees)
  2. MP3000-90 
  3. MP2000-90 - 25.8 gph (90 degrees)
  4. MP800SR-90 - 13.8 gph (90 degrees)
  5. MP800SR-90 - 25.2 gph (180 degrees)
  6. MP800SR-90 - 25.2 gph (180 degrees)
  7. MP800SR-90 - 25.2 gph (180 degrees)
  8. MP2000
  9. MP3000-90 

      Total 141 gph

Our total water usage for this zone is calculated at 141 gph, which is comfortably within our available water use. Sure we could have looked at adding nozzle 2, but it is a much higher output at over 50 gph, which may have stretched your water source a little thin. Zone 1 Done!!

 

Let’s move on to Zone 2.