1Southwest Florida Water Management District, 2002. Effective Use of Reclaimed Water Demonstrated to Offset Water Demand »
The District uses 300 gallons per day per single family household as the average potable offset by switching to reclaimed water for outdoor irrigation purposes. This quantity assumes an average of 2 irrigation cycles per week, irrigating 3 zones per cycle. Each zone is assumed 30 minutes of irrigation and is to be aggregated into the final volume of time for the cycle. For example, if one has 3 zones account for 90 minutes of irrigation. Using these assumptions 300 gallons can be multiplied by 7 to get the weekly total and dived by 2 to get the weekly total for one irrigation cycle. One irrigation cycle can be divided by the assumed 90 minutes of irrigation to acquire the minutes per a gallon for an irrigation cycle. This value also assumes that a rain sensor shut device is present.
300 gallons per single family household per day × 7 days = 2100 gallons per week
2100 gallons per week / 2 irrigation cycles = 1050 gallons per irrigation cycle
1050 gallons per irrigation cycle / 90 minutes = 11.67 gallons per minute per irrigation cycle
2Southwest Florida Water Management District, 2008. Evaluation of Soil Moisture-Based On-Demand Irrigation Controllers: Final Report. »
This report prepared for and funded by the District quantifies the savings potential of using rain sensor shut off devices for automatic irrigation systems. Outlined in the report are two values for savings, a percent savings for wet weather conditions (34%) and percent savings for the dry season (13% and 24%). The value used to calculate the gallons saved in the water use calculator is 24%. This value was used to better represent an estimate of savings and not to be biased towards one particular season. However, since the value (300 gpd) given through the Effective Use of Reclaimed Water Demonstrated to Water Demand report included having rain sensor shut devices and the flow rate of water used to irrigate doesn’t change based upon water savings, the percent (76%) unsaved was factored back into the formula to acquire the quantity of water used without a rain sensor. This is done because savings associated with rain sensors are based upon the offset of time spent irrigating due to wet hydrologic conditions, rather than based on lowering the flow rate of the irrigation system itself.