Rainwater Harvesting in a Drought

Dan Behringer & Phyllis Muska

Texas Master Naturalist – Hill Country Chapter

October 26, 2011

Why rainwater?Conserve water resources to help preserve water levels in the aquiferSuperior water quality – softer water means less detergent, no lime/calcium buildup on shower walls and appliancesPlants and landscape prefer rainwaterMay be more dependable than a wellSave money if using city water –30-50% of total water used by a typical home is for landscape wateringReduces volume of storm water during heavy rain eventsMay lessen erosion from runoffNo chemicals or additives necessaryIt tastes good!

What are the components of a Rainwater Harvesting system?

Collection

Conveyance

Storage

Treatment

System Components

Collection –Catchment surface: the collection surface from which rainfall runs offConveyance from catchment surface –Gutters, downspouts, and pipe channel water from the roof to the tankStorage –One or more tanksConveyance to point of use –Delivery system gravity-fed or pumped to end useTreatment/purification –

Initial filtration – Leaf screens, first wash diverters, and roof washers remove debris and dust from the captured rainwater before it goes to the tankFor potable systems, filters, UV lights, and other methods make the water safe to drink

System Schematic

Catchment Surface #1

Phase 1 – 550 sq ft garage – 1996

Catchment Surface #2

Phase 2 – 2000 sq ft house - 2001

Catchment Surface #3

Phase 3 – 2003

2400 sq ft barn

Gutters and Downspouts

Gutters and Downspouts

Fiberglass Tanks with Food-Grade LinerPhase 1: 5,000 gal

Phase 2: 10,000 gal

Phase 3: 10,000 gal

Tanks must be same height!

Polyethylene tanks

Riverside Nature Center – 5000 gallons

Metal tanks

Pioneer tanks from Australia

First Wash System – standing pipe

First Wash System – rain barrel

First Wash System – the Eliminator

Cost ~$1200

First Wash System – vortex filter

First Wash System – Filtration box

Fiberglass box with removable filters – $600-$800

Floating Cistern Filter

~$450

Grundfos MQ pump

~$575

Filters

UV light

- Sanitron Ultraviolet S-37B

- UV disinfection to kill bacteria

- 12 gpm

- Built-in bulb cleaning apparatus

- ~$900

Pump, Filtration and UV Light

~$2000

Quick-Connect Valve

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!

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

. . . 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

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

Summer 2009 UTHSC StudyUT Health Science Center at Tyler - Potable Rainwater Study - Summer 2009

Rainwater Sampling Results

Participant: Behringer/Muska

Date of Sampling: 8-8-09

Test Result pre-filtration Result post-filtration Recommended Limit of Detection

(LOD)

pH 6.5 5.9 6.5-8.5

alkalinity ppm 20 20 <150 mg/L

hardness ppm 0 0 >120 mg/L=hard water

free chlorine ppm 0 0

total chlorine ppm 0 0 <4 ppm

nitrates ppm 0 0 <10 ppm

nitrites ppm 0 0 <1 ppm

conductivity µS/cm 13.93 16.68 <1000 µS/cm

total dissolved solids mg/L 6.1 7.5 <500 mg/L

total bacteria light growth, <100 0 <500 colonies/ml

coliform bacteria 0 0 0

lead ppb 2.813 not detected <15 ppb .2622 ppb

copper ppm not detected 0.0723 <1.0 ppm .0057 ppm

iron ppm not detected not detected <0.3 ppm .003 ppm

zinc ppm 0.2694 0.357 <5 ppm .0006 ppm

aluminum ppm 0.0198 not detected <0.05 to 0.2 ppm .0162 ppm

arsenic ppm

Heavy metal testing was performed by the Water Analysis Lab at Stephen F. Austin University

CostsRough 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

Maintenance

Change filters monthly/quarterly ~$100/yr

Clean gutters as needed –1-2 times/year

Replace UV bulb every 12-14 months ~$80-$100

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

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

Non-potable applications

Collecting water for irrigation purposes: can be as simple as running a hose from a downspout to a rain barrel

Non-potable applicationsRain “pillow” – 1000+ gallons stored in a bladder under the deck

10' x 8' x 2' tall (when filled) 1000 gallons ~$2500

Non-potable applications

Guzzler – watering station for wildlife and/or livestock

Water Conservation

Key to preserving our precious water resourcesCultivate a mindset for conservation until it becomes second nature – use, re-use, then use again!Pay special attention to these guzzlers:

ToiletsAppliances Landscape wateringSprinkler systems

Avoid bare dirt – prevent runoff and erosion Landscaping: use native grasses, shrubs, forbsCollect condensate from A/C

Additional Resources

http://www.twdb.state.tx.us/iwt/rainwater.asp

http://www.greenbuilder.com/sourcebook/Rainwater.html

http://www.rainwatercollection.com

Taste test

Have a sample of our ‘cloud juice’ – fill your water bottle!