Here comes the real fun part about putting in irrigation. The calculations! Doing these calculations is key in determining zones, how many times you water per week and for how long.
The first thing you want to do is create zones for each basic type of plant. For us we have a zone for fruit trees, a zone for our drought tolerant landscape, and 2 zones for our vegetable garden. We are using Rainbird Xerigation Control Zone Kit ASVF-LF-075 for each of our zones. We are also using 3/4″ SCH40 pipe. I generally don’t recommend using smaller pipe because you get better pressure with larger pipe and it’s not that much more expensive. Generally with drip you won’t need to go above 3/4″ pipe.
Now what you want to do is determine your gallons per minute (GPM) from your water lines. The easiest “low tech” way to do this is with a timer and a 5 gallon bucket. Turn your water spigot on full blast and then right when you put the bucket under it start your timer. Stop the timer when the bucket is filled. Divide the 5 gallons by the time in minutes to find the flow rate. If it takes 30 seconds to fill the bucket then your water is running at 10 GPM. Or 5 gallons/.5 minutes. If it takes 45 seconds then your water is 5 gallons/.75 minutes = 6.7 GPM. However, if you are using a drip system valve and pressure regulator, it will bring your flow rate down to 5 GPM. You just want to make sure that your household flow exceeds the top flow allowed by the valve.
Next you want to figure out which type of irrigation system you want to use. We are going to assume that you will be running a drip system at 5 GPM. Manufacturers will have this information with their products as it can be slightly different than what I list. The information I’m giving is just a general guideline. If you use drip emitters each emitter will have specified rate, such as 1/2 gallon per hour (GPH). So 120 emitters would equal 1 GPM. (60 min/.5 gallons per hour = 120 emitters) You can run 600 – 1/2 GPH emitters per valve. T-tape runs at 40 GPH per 100′ or .67 GPM. However, runs of T-tape should not exceed 350′, which is why we have to have two control zones. 1/2″ soaker hose runs at 54 GPH or .9 GPM per 100′ so you cannot exceed 450 feet of run per zone. Bubblers, which we use on our trees run at 13 GPH or .22 GPM. We can run 22 bubblers on that zone.
Scheduling (how often for how long to apply water) is more difficult to determine because it is dependent on so many factors such as heat, precipitation, humidity and evapotranspiration. And each of those factors are different depending on where you live. The easiest way around this is to get a Smart Controller that has a subscription to weather data and will turn on as needed. If you don’t want to spend the extra on a Smart Controller you can refer to the chart on this site for basic scheduling: http://www.dripdepot.com/article/determining-drip-irrigation-watering-schedule
Hopefully I didn’t lose you. If you have any questions or need help doing zones just let me know and I’ll be happy to help you out. For non-drip areas the zoning gets much more complicated and would be too much to discuss on this blog.