Well Irrigation Systems
We have an extensive list of FAQs (Frequently Asked Questions). If you have questions you don't see answered below, look for the answer in our FAQ section.
Supplying an irrigation system from a well
If you plan to use an existing well to supply your sprinkler system, this page may be the most important page at this site for you to read. It explains the major issues relating to irrigation systems supplied by wells.
Selecting a controller and defining a schedule
When scheduling the system, you'll need to take care to insert a delay between stations that is adequate to allow the well time to recharge. You'll also have to consider what might happen if, for instance, you set the seasonal adjust feature to a higher value. For example, if you can water for only one hour before drawing your well down too far, then a one hour station time with a 200% seasonal adjust factor will result in a two hour station time, endangering your pump! You can address this either by setting the maximum station time to 30 minutes and allowing the seasonal adjust feature to be adjusted through it's full range (usually a maximum of 200%), or you can just avoid using seasonal adjust feature at settings over 100%. This example is based on a maximum watering time of one hour. If your pump/well combination allows more or less time, the station time and seasonal adjust settings will have to be changed accordingly.
First, you need to establish what the steady state flow and pressure is for your pump when the well is relatively low, and base your design on that flow rate. Second, you also need to know how long you can sustain that flow before you draw air into the pump, and how fast the well can recharge. Your system design must not require more flow than your pump can deliver at steady state, and your irrigation schedule must not demand water for too long before allowing the well to recharge. The first issue is handled by designing the system to operate within the limits of your well and pump, while the second issue is handled by the proper selection and programming of a controller.
You'll need to determine what flow and pressure your pump can deliver. The best approach is to have these measurements made by a person in your area who installs wells. If you can't locate a well service, you can do this yourself, although you need to recognize that any mistakes you make due to unfamiliarity can cost you a lot more in equipment failures than you will spend to get these measurements made for you. If you choose to do these measurements yourself, measure the flow rate of the pump at the max and min pressure switch settings for your tank. If you don't have a tank, make flow rate measurements at 50 and 70 psi if you plan to use rotors, or rotors and spray sprinklers. If you plan to use ONLY pop-up spray sprinklers, make flow measurements at 40 and 60 psi.
To do this, install a tee and valve where you want to feed the sprinkler system, then open the valve. Adjust the flow rate through the valve so the tank can't QUITE reach the shut-off pressure, then read the flow rate by measuring the water in a large bucket and timing how long to fill it up. Make sure the system is at steady-state when you read the flow, in other words, wait a long time to make sure the tank level is steady during the test. Don't be fooled by the tank dumping a huge load of accumulated water, leading you to think the pump can keep that up forever! Next adjust the valve so the pressure tank runs near the low end of the switch range (the pressure at which the switch turns ON the pump), and measure the flow again at steady-state.
You should then design to work with all stations using a flow rate about half way between the two flow rates.
Do it right the first time