Travis Irrigation Plans and Supply


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.

Backflow protection
If your pump is connected to a potable water system at any point, you will need to install a backflow preventer between your irrigation system and your potable water. The grade of backflow preventer required is defined by local plumbing codes, so check with the building permit people in your area for what's required. Often, a lower grade of protection is accepted when you're connecting to a private well as opposed to when a system is connected to public water in the same area. The logic must be that they don't care that much if you poison yourself, but they REALLY don't want you to poison all your neighbors! Ask about installing a higher grade of backflow preventer than required on your sprinkler system if you value your health more than your neighbor's health.

Selecting a controller and defining a schedule
There is one feature seldom found on irrigation controllers that is usually necessary to have on any system that is fed by a well. It's called "delay between stations" and it allows you to set a variable length delay between stations to allow a well to recharge as explained below (or to allow a slow valve to close in low pressure situations). We offer two controllers with this feature; the Hunter ICC controller (delay between stations from 1 sec to 1 minute 40 sec) and the Rain Bird ESPLX series (delay between stations from 1 sec to 9 hours). The ICC controller has a "cycle and soak" feature that can be used in some circumstances to achieve longer delays between watering periods, but if your well needs long recharge times, the ESPLX series may be a better choice for you. Most wells that were not primarily designed for irrigation will provide relatively modest steady state flow rates, requiring relatively small stations, and a lot of them. It's no coincidence that the two controllers we offer with the "delay between stations" feature are also available with a large number of stations. The ESPLX+ controller is available up to 24 stations. The ICC controller is available with up to 48 stations, although the delay between stations option limits the program to much shorter values than the ESPLX series.

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.

Flow rates
Determining flow rates is a very important step in defining your whole design. Your system may have a tank that provides a large flow for a few minutes, but after the water stored in the tank is exhausted and the pump is supplying the system on it's own, a lower "steady state" flow will be available. Then, if the well is drawn down after watering for too long, it could even pull air into the pump (this is bad!) and the flow will plummet. Your pump could overheat and burn up if this happens.

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
By making note of the issues discussed on this page, and designing the system to operate within these limits, you will save yourself untold grief later. People who are not careful with these points have to break all their stations into smaller pieces, run new wires into the field, and upgrade to a larger controller. By designing the system around your pump, and selecting one of our excellent controllers, you have the potential to install a system as nice as any professional could do at a fraction of the cost. Do it right the first time, and you'll save yourself a lot of money, time, and effort. After you have looked around at other controllers, we think you'll find the the Hunter ICC controller and the Rain Bird ESPLX series controllers are tops for well installations.

You'll also find some information relevant to well installations on our pump page.

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