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Rainwater harvesting102611

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Components of a rainwater harvesting system and how to calculate tank size, etc.

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Rainwater harvesting102611

  1. 1. Rainwater Harvesting in a Drought Dan Behringer & Phyllis Muska Texas Master Naturalist – Hill Country Chapter October 26, 2011
  2. 2. Why rainwater? <ul><li>Conserve water resources to help preserve water levels in the aquifer </li></ul><ul><li>Superior water quality – softer water means less detergent, no lime/calcium buildup on shower walls and appliances </li></ul><ul><li>Plants and landscape prefer rainwater </li></ul><ul><li>May be more dependable than a well </li></ul><ul><li>Save money if using city water – 30-50% of total water used by a typical home is for landscape watering </li></ul><ul><li>Reduces volume of storm water during heavy rain events </li></ul><ul><li>May lessen erosion from runoff </li></ul><ul><li>No chemicals or additives necessary </li></ul><ul><li>It tastes good! </li></ul>
  3. 3. What are the components of a Rainwater Harvesting system? <ul><li>Collection </li></ul><ul><li>Conveyance </li></ul><ul><li>Storage </li></ul><ul><li>Treatment </li></ul>
  4. 4. System Components <ul><li>Collection – Catchment surface: the collection surface from which rainfall runs off </li></ul><ul><li>Conveyance from catchment surface – Gutters, downspouts, and pipe channel water from the roof to the tank </li></ul><ul><li>Storage – One or more tanks </li></ul><ul><li>Conveyance to point of use – Delivery system gravity-fed or pumped to end use </li></ul><ul><li>Treatment/purification – </li></ul><ul><ul><li>Initial filtration – Leaf screens, first wash diverters, and roof washers remove debris and dust from the captured rainwater before it goes to the tank </li></ul></ul><ul><ul><li>For potable systems, filters, UV lights, and other methods make the water safe to drink </li></ul></ul>
  5. 5. System Schematic
  6. 6. Catchment Surface #1 <ul><li>Phase 1 – 550 sq ft garage – 1996 </li></ul>
  7. 7. Catchment Surface #2 <ul><li>Phase 2 – 2000 sq ft house - 2001 </li></ul>
  8. 8. Catchment Surface #3 <ul><li>Phase 3 – 2003 </li></ul><ul><li>2400 sq ft barn </li></ul>
  9. 9. Gutters and Downspouts
  10. 10. Gutters and Downspouts
  11. 11. Fiberglass Tanks with Food-Grade Liner <ul><li>Phase 1: 5,000 gal </li></ul><ul><li>Phase 2: 10,000 gal </li></ul><ul><li>Phase 3: 10,000 gal </li></ul><ul><li>Tanks must be same height! </li></ul>
  12. 12. Polyethylene tanks <ul><li>Riverside Nature Center – 5000 gallons </li></ul>
  13. 13. Metal tanks Pioneer tanks from Australia
  14. 14. First Wash System – standing pipe
  15. 15. First Wash System – rain barrel
  16. 16. First Wash System – the Eliminator Cost ~$1200
  17. 17. First Wash System – vortex filter
  18. 18. First Wash System – Filtration box Fiberglass box with removable filters – $600-$800
  19. 19. Floating Cistern Filter ~$450
  20. 20. Grundfos MQ pump ~$575
  21. 21. Filters
  22. 22. UV light <ul><li>Sanitron Ultraviolet S-37B </li></ul><ul><li>UV disinfection to kill bacteria </li></ul><ul><li>12 gpm </li></ul><ul><li>Built-in bulb cleaning apparatus </li></ul><ul><li>~$900 </li></ul>
  23. 23. Pump, Filtration and UV Light ~$2000
  24. 24. Quick-Connect Valve
  25. 25. What happens if it doesn’t rain? <ul><li>1” rain -> 600 gallons for each 1000 sq ft collection surface, depending on efficiency </li></ul><ul><li>2500 sq ft house: 1500 gallons per inch of rain </li></ul><ul><li>Add a barn and garage to the system to total 5000 sq ft = 3000 gallons with just 1” rain! </li></ul>
  26. 26. It’s All About Storage . . . <ul><li>2007: 45” of rain </li></ul><ul><li>135,000 gallons went through system </li></ul><ul><li>Our annual usage: approximately 36,000 gallons </li></ul><ul><li>So . . . almost 100,000 gallons got away! </li></ul><ul><li>. . . </li></ul><ul><li>2011: 6” of rain over last 12 months </li></ul><ul><li>May need to have water hauled in </li></ul>
  27. 27. . . . And timing <ul><li>Figure approximately 50-75 gallons per day per person </li></ul><ul><li>For 2 people: 3000-4500 gallons/month requires an average of 1”-1½” rain/month </li></ul><ul><li>25,000 gallons = 7-8 month supply </li></ul><ul><li>1996 – summer 2011: never below a two-month supply </li></ul><ul><li>To calculate capacity needed, figure on historic maximum number of days with no rain </li></ul>
  28. 28. How pure is the water? Is it really OK to drink? <ul><li>5-micron spin filter </li></ul><ul><li>3-micron charcoal filter </li></ul><ul><li>UV light </li></ul><ul><li>Tests almost the same as distilled water </li></ul><ul><li>pH around 6.0 </li></ul><ul><li>Tests available through UGRA, LCRA </li></ul>
  29. 29. Summer 2009 UTHSC Study
  30. 30. Costs <ul><li>Rough estimate for 20,000 gallon system, 2000 sq ft footprint, potable water: </li></ul><ul><ul><li>Two fiberglass, polyester resin-lined 10K tanks @ $7,500: $15,000 </li></ul></ul><ul><ul><li>Or one metal Pioneer tank 20K: $12,000 </li></ul></ul><ul><ul><li>Gutters and downspouts: $500 </li></ul></ul><ul><ul><li>First wash: $600-1500 per inlet </li></ul></ul><ul><ul><li>Pump: $600 </li></ul></ul><ul><ul><li>Filtration and UV: $1000 </li></ul></ul><ul><ul><li>Total: $15,000-$20,000 + delivery + labor – comparable to drilling a well in many areas </li></ul></ul>
  31. 31. Maintenance <ul><li>Change filters monthly/quarterly ~$100/yr </li></ul><ul><li>Clean gutters as needed – 1-2 times/year </li></ul><ul><li>Replace UV bulb every 12-14 months ~$80-$100 </li></ul>
  32. 32. It’s Catching On . . . <ul><li>Recent survey by TRCA – data from over 1,000 systems with total capacity of over 15,000,000 gallons </li></ul><ul><li>More than 6,000 rain barrels were installed through the City of Austin’s incentive program from 1995-2005 </li></ul><ul><li>More than 100,000 residential systems in the US installed by professionals </li></ul><ul><li>Countless do-it-yourself systems in place </li></ul>
  33. 33. <ul><li>Kroc Center in Kerrville – 135,000 gallons </li></ul><ul><li>Boerne Champion High School </li></ul><ul><li>Willow City Volunteer Fire Department –24,000 gallon system: gravity flow dispensing system can fill a 400-gal tank on a brush truck in 2 minutes </li></ul><ul><li>Riverside Nature Center 5,000 gallon system collecting off ~4500 sq ft – takes only a 2” rain to fill </li></ul><ul><li>Menard Library – with demonstration gardens </li></ul><ul><li>Lady Bird Johnson Wildflower Center in Austin – 70,000 gallons </li></ul>Commercial applications
  34. 34. Non-potable applications <ul><li>Collecting water for irrigation purposes: can be as simple as running a hose from a downspout to a rain barrel </li></ul>
  35. 35. Non-potable applications <ul><li>Rain “pillow” – 1000+ gallons stored in a bladder under the deck </li></ul>10' x 8' x 2' tall (when filled) 1000 gallons ~$2500
  36. 36. Non-potable applications <ul><li>Guzzler – watering station for wildlife and/or livestock </li></ul>
  37. 37. Water Conservation <ul><li>Key to preserving our precious water resources </li></ul><ul><li>Cultivate a mindset for conservation until it becomes second nature – use, re-use, then use again! </li></ul><ul><li>Pay special attention to these guzzlers: </li></ul><ul><ul><li>Toilets </li></ul></ul><ul><ul><li>Appliances </li></ul></ul><ul><ul><li>Landscape watering </li></ul></ul><ul><ul><li>Sprinkler systems </li></ul></ul><ul><li>Avoid bare dirt – prevent runoff and erosion </li></ul><ul><li>Landscaping: use native grasses, shrubs, forbs </li></ul><ul><li>Collect condensate from A/C </li></ul>
  38. 38. Additional Resources <ul><li>http://www.twdb.state.tx.us/iwt/rainwater.asp </li></ul><ul><li>http://www.greenbuilder.com/sourcebook/Rainwater.html </li></ul><ul><li>http://www.rainwatercollection.com </li></ul>
  39. 39. Taste test <ul><li>Have a sample of our ‘cloud juice’ – fill your water bottle! </li></ul>

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