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Rainwater harvesting102611


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

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

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  • It's not nearly as much fun harvesting rainwater in a drought as it is when it's raining . . . but it can be done We are not engineers or professionals, and we’re not here to sell anything – we’ll basically just show you how our system is set up and describe some areas we might have done differently if we knew then what we know now – we hope you can benefit from our mistakes We bought our land in 1995 and started building in 1996 – so we’ve been collecting rainwater for over 14 years – no well We don’t make any particular recommendations for systems or suppliers – but we will mention some names for additional information and help Ask how many already have some kind of collection ? MNs – Peña, Stanley, RNC, Clyburn, Sawin, Collins, Y Carlyle, Jim & Janet Lindley, Reidun H,
  • Texas’ population is projected to more than double to about 45 million people by 2060, with much of that growth projected in the Hill Country area More than 57,000 more people are coming to live in the Hill Country every year. The 17-county region’s current population of 3.1 million is projected to climb to at least 4.3 million by 2030.
  • Acceptable roof types: Metal – galvalume (55%aluminum, 45% zinc alloy) Clay or concrete tiles – but may contribute to a 10% loss due to texture, inefficient flow, or evaporation Composite – not appropriate for potable systems Slate – OK but expensive
  • Dan Note vinyl window screens at downspouts Gravity-flow system – flows from gutters to tanks, then back to pump Point out components: Catchment Conveyance Storage Filtration/purification
  • Use footprint, not actual surface area
  • Most common: half-round PVC, vinyl, pipe, galvanized steel seamless aluminum – more expensive Vinyl: Relatively easy to clean, doesn’t need painting – Plastmo available in different colors (show sample) Note roof design lends itself to very simple guttering (happy accident – not what we had in mind when designing garage)
  • Tanks must be level! Our system – built in multiple phases, with multiple inlets and multiple filtering mechanisms Doesn’t have to be so complicated – plan, and keep it simple! Preferable to use fewer tanks Our tanks are polyester resin-lined fiberglass – tank at Riverside is polyethylene (?) ~ $3100 for 5000 gal
  • In addition to screens over downspouts, there are two basic types of first wash systems: capture type – either a tube or tank – price varies from $25 to $1200+ – PVC pipe in photo ~$25 + labor All of the first wash systems require attention after each rain event of any size – filters must be kept clean or system will clog up, back up, and overflow
  • tank type of first wash ‘ Booley eliminator’ from Tank Town in Dripping Springs – top of the line ~$1200 + installation
  • The vortex rainwater fine filter is typically installed in the underground piping system to remove debris from the storm water system.Used in installations where multiple downspouts are connected together to a single pipe into the vortex filter. The vortex rainwater filtered water can be used for site irrigation, toilet and urinal flushing, janitorial use, laundries, fire protection, evaporative cooling tower make-up, process water or other non-potable uses.
  • Also – filter boxes or barrels – example of this on Riverside’s system – ~$50
  • Additional filtering option for use in tank – filters water drawn from 12-16” below surface, where the ‘best’ water is thought to be Kits for this filter ~$450 Must have special ‘full-through’ coupling on your tank
  • combines a pump, motor, pressure tank, and controller into one integral unit 1HP pump is self-priming, with built-in check valve Built-in overheat and dry pump protection Maximum 17 gpm at a constant 55 psi Specifically designed for drinking water applications – expressly approved for use with rainwater - ~$600 Grundfos: Danish company founded in 1945
  • 5-micron sediment spun-fiber filter 3-micron activated charcoal filter – 9 gpm two ball valves permit two pressure gauges: one to measure incoming pressure, one for outgoing pressure – by monitoring difference in pressure, you can tell when filters need changing rule of thumb: change spin filter monthly, charcoal filter quarterly spin filter shows when it needs changing ~$325 for filter assembly
  • Available as pre-plumbed setup with pressure gauge and ball valves, mounted on plywood over a galvanized steel panel ~$2000
  • Provides extra protection in the event of a fire – ready supply of water May be eligible for discount on homeowners insurance Check with your own fire dept for correct size
  • Phyllis This is the first question everyone always asks . . . No voodoo, just arithmetic. Depending on rainwater means having enough storage to collect lots of rain when it does rain. You need to have enough storage capacity to get you through the longest (historic) period with no rain – ~100 days in this area. Then figure your usage – we estimate ~100 gal/day, so 100 days with no rain means we should be able to get by with 10,000 gallons storage.
  • For our area, figure on 100 days with no rain Drought of record: worst year had 12” total rainfall Last few years in Hill Country: ~15” in 12-month period On land: 1” rain -> 27,154 gal/acre (208.7’x208.7’, or 43,560 sq ft)
  • based on our system, adjusted for today’s prices
  • Dan
  • Phyllis - Now required on new buildings >2500 sq ft in Santa Fe - Was illegal in Colorado until 2009 – now OK with restrictions - Illegal in Utah and Washington unless landowner has water rights
  • Toilets – approx 30% of all indoor water use Use low-flush toilets – 1.6 gal New toilets with two flush options Check for leaks – food color in tank, wait 15 minutes – if bowl is colored, flapper may need to be adjusted or replaced Running water in bathroom and kitchen sinks Turn off water while brushing teeth or shaving Rinse dishes and vegetables in pan of water rather than running water Compost food scraps rather than running garbage disposal When replacing an appliance, but a water-efficient model that offers different cycles and uses less energy Landscape can account for 20-50% of residential water use ideal application for rainwater collection! Filtering not necessary reduce turf areas – easier to maintain and lower water use keep a height of 2.5-3” on grass areas – protect roots from heat stress, reduce loss of moisture to evaporation plant native and well-adapted plants that won’t need to be watered once they are established Drip irrigation more efficient than sprinkler If building, consider adding circulating pump for hot water
  • Cloud Juice samples other MNs doing presentations on rainwater collection: Jim & Priscilla, Sandy & Raul also – Billy Kniffen, John Kight each one is different, so try to hear any/all of them
  • Transcript

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