b'STORMWATERCATALOGIf the catchment area is comprised of a variety of differentEXAMPLE OF SIZINGsurfaces, with different runoff coefficients, then a weighted average value should be calculated. A warehouse facility in Houston, TX plans to use A = Drainage Area (sq.ft.), the area that drains to the designcollected rainwater to irrigate the landscaping on the point of interest property site. The building is a rectangular structure, 150 ft x 50 ft, with a flat roof. The landscaping area A conversion factor of 7.48 gallons of water per one cubicconsists of multiple flowerbeds and a large grassy foot of area will be necessary to change the final resultregion with a total combined area of 4,500 square from cubic feet to gallons. feet. The runoff coefficient is determined to be 0.80. Annual precipitation from demographics of the Determining Demand: There are two types of waterregion show 49.8 inches per year is received.demands: What is the optimum size for the rainwaterstorage tank?Indoor demand includes the number of people in theTo determine supply using the Rational Method building, the number of hours per day the building isequation:occupied, the numbers and types of toilets/urinals inQ = CIAplace, etc. Design considerations would be the same as the demand from a fresh water supply line. The additionalRunoff Coefficient (C) = 0.80concern would be the creation of required water pressureRainfall Intensity (I) = 49.8 inches per year / 12 months and any pretreatment from the rainwater storage tank. = 4.15 inches/monthCall ParkUSA Engineering for design help. Roof area (A) = (150 x 50) = 7,500 sq.ft.Outdoor demand consists of the volume of water toConversion factor - 7.48 gallons of water per one cubic RAINWATERHARVESTINGbe used for irrigation of grasses and landscaping, waterfoot of area.fountains, or other water features. Different types ofTo determine the average monthly supply in gallons/vegetation have different water requirements. Researchmonth, first convert the rainfall intensity fromis required for the specific design features of the system4.15 inches per month to feet per monthin question. See the example of sizing for demand forI = 4.15 in/mo. divided by 12 in/ft = 0.3458 ft/mo.additional information regarding this aspect. Therefore, Q = C x I x A, now can be calculated:Q = 0.80 x 0.3458 ft/mo. x 7,500 sq.ft. xMAINTENANCE 7.48 gal / cu.ft. = 15,520 gallons / mo.ParkUSAs RainTrooper Systems are designed to beQ = 15,520 gallons per monthmonthly supplyeasily operated and maintained. Regular and on-goingof rainwaterinspection of the system should be conducted, whichTo determine the demand for the rainwater, calculate includes visually inspecting all system components andthe amount of water planned to be used in a one cleaning of catchment area, gutters, and filters as needed.month period. While the amount of water needed Pumping the first-flush system should be done quarterlyfor lawn maintenance varies depending on current initially, and then adjusted to a maintenance scheduleweather factors, the climate for the area, and the time based on site characteristics and environment. A pumpof year, the general rule of thumb is for the lawn to truck may be utilized to remove grit and trash fromreceive 1 inch of water per week during dry conditions. the storage tank. Maintenance of the pump is done asUsing the following conversion calculation:required by pump manufacturer requirements. Typical pump maintenance includes cleaning of debris on the1 in/wk12 in/ft x 7.48 gal/ft3 = 0.623 gal/ft2suction screens of the pump. This demand equates to 0.623 gallons per square foot of lawn area each week. Therefore, determine the average monthly demand in gallons/month:Landscaping area = 4,500 square feetIrrigation Rate = 0.623 gal/ft2 per week x 4,500 ft2 = 2,803 gallons/week2,803 gal/wk x 4.2 wks per mo. = 11,773 gal/mo.The average monthly demand for rainwater is approximately 11,775 gallons.The supply of rainwater available each month exceeds the demand planned for its use.Sizing a 16,000 gallon RainTrooper for this application would create a reserve of approximately 4,000 gallons per month.INFO@PARKUSA.COM|888-611-7275|WWW.PARKUSA.COM 105'