Whole House Rainwater Harvesting: Capturing and Using Rainwater for Potable Applications
For a number of reasons, rainwater harvesting is preferred not just for landscape irrigation but for whole house potable uses as well. Here we present advanced design concerns and strategies including reliability, safety, regulatory and legal issues.
Presented to the Conservation Coordination Consortium hosted at Tampa Bay Water, October 13, 2010
LID = Low Impact DevelopmentSite retention = reduced demand on stormwater processingA good strategy would be to, not only conserve water, but also to use an alternative water source (rainwater) for irrigation, and save our precious potable drinking water for drinking and other indoor uses.Not as cost-effective for small volumes, but for large = huge potential financial savings
Simple supply and demandRapidly and continuously growing region = resource demandsIncreased demand on traditional water supplies (ground/surface water) = growing reliance on “innovative” supplies (desal)Groundwater demand leads to unstable geology (sinkholes)??Increased pollution = increased treatment efforts (surface waters)As demand on “innovative” supplies increase, cost of blended product increasesRHS is an alternative supply that reduces demand on produced water resources
How do we prolong development of new water supplies?As a part of effective conservation: RAINWATER HARVESTING
There are many uses for rainwater. Irrigation would be the application requiring the least amount of treatment before use.All contribute to offsetting municipal supplies.
HEALTH is #1 priority. (repeated for emphasis).Treatment to potable standardsTesting to ensure standards are metReliable (don’t want loss of water during shower)Ease of serviceRegulatory = building, health, etcProbably incomplete list
As it pertains to water qualityBig or small, residential or commercial, the harvesting system will have these components.Focus on: 1) pre-treatment; 2) Treatment; 3) reliability
The roof is what is used as the catchment area. (there are other surfaces, e.g. permeable driveways, swales, etc… but for simplicity, stick with roofs)Its size dictates how much rainwater can be captured. Material affects initial water quality.The slicker, the better
Common senseGarbage in, garbage out
First line of defense.Not reliable. When designing RHS, assume no leaf guards.Keeping limbs and leaves away from catchment area and from clogging conveyance is important in keeping cistern water quality pure.These products reduce maintenance needs while preventing debris from entering the cistern.
First-flush or roof washerVolume to be diverted depends on contaminant loadMinimal (no large overhanging trees)= ~ 10 gallons/1000 sfHeavy (large overhanging tree canopy) = ~ 50+ gallons/1000 sf
You will notice that cisterns have a lot pipes going in and out of them. This configuration can vary, but generally there will be an inlet, an outlet, an overflow and drain valve. A manway is also necessary for maintenance/cleaning. Never go inside alone or without a plan on how to get out.Inlet, outlet and overflow are self explanatory. Overflow:Engineering drainage design may need to come into play here. Common sense dictates for overflow to be directed away from tank/buildings where volume of water won’t cause erosion, flooding, carry organic material (especially if animals are present) into wells or water sources, cause standing water for long periods (mosquito breeding), etc. Over flow can be directed towards in place drainage system or can also be allowed to percolate into the ground via french drain, etc. Passive use of the overflow rainwater is desirable.Overflow outlets can be configured in different ways. If the overflow outlet draws from the bottom, it should be vented to prevent siphoning. Overflow outlets and vents should be equipped with a fine mesh screen to prevent mosquito entry.Anaerobic/Sediment zone is located in the bottom 6” or so of the tank. Here is where the ‘dirtier’ water and sediment tends to collect. Avoid drawing water from this portion of the tank.A hose bibb or drain valve is needed in order to drain the tank if needed. Bibb should be elevated 6” or so. Solids tend to accumulate at the bottom so elevating will help avoid clogging.The floating suction filter will allow water to be extracted in the cleaner area of the tank. Particles either settle at the bottom of the tank or float on top. Thus, the filter on the end of the hose will filter the remainder of the particles before sending the water to the irrigation system.Important to make sure all openings are sealed properly to avoid (1) mosquito infestation (2) animal intrusion and (3) children from entering the cistern.Tank should be placed on a level, stable foundation. This may consist of gravel or concrete pad. FACT: Water weighs 8.34 pounds per gallon. A 1000 gallon cistern can weigh up to 8340 gallons when full. Imagine what would happen if an unstable tank tips over.
Pump:Make-up: valve to switch to other water source when tanks run dry or water quality is low-In this case, normally open = fail-safe redundancy
Dual pump for increased demandNo less than 3 backflow preventers in this roomSwitching controls for make-up water
NOTE 1: Dye injection for toilet flushing, per greywater plumbing codes. If treated for potable, must meet EPA standards, approval from health, water resources departmentsNOTE 2: Backflow to prevent public water supply (if cross-connected to municipal water)UV preferred for small-scale RHS because non-chemical (e.g. chlorine) and doesn’t waste water (e.g. RO)NSF 53: Guideline for removal of cysts: 0.5 um carbon.NSF 55A: Guideline for ultraviolet treatment of previously untreated surface waters. Must be pre-treated to NSF 53.All RWS potable systems use components that meet NSF 53 and 55A (also 61: components safe for drinking water)
Pump3-stage sediment/carbonUVNote: makeup controlsFloat switch and UVT switch wired in series to NO valve on mains water
Complex systems require collaboration and knowledge of various regulations, laws and guidelines
Engineer is your best friendMUST HAVE QUALITY ENGINEERINGIncludes meetings with building department officials as needed. Keep everyone in the loop.
Commonly, rainwater is considered as “graywater” for lack of a better definition. However, according to IPC 2006 (Appendix C: C101.9), Gray Water is defined asGray Water: “waste discharged from lavatories, bathtubs, showers, clothes washers, and laundry trays.”IPC 2006; Appendix C: C101.9Since water collected in RHS is not supplied by any of the sources listed in this definition, an argument can reasonably be presented that rainwater is NOT graywater. As such, RHS should not be subject to the same code interpretations as graywater.Since surface waters (including stored rainwater) are suitable as private water supplies, the only limitations on their use for the proposed applications pertain to their potability.Potable Water: “Water free from impurities present in amounts sufficient to cause disease or harmful physiological effects and conforming to the bacteriological and chemical quality requirements of the Public Health Service Drinking Water Standards or the regulations of the public health authority having jurisdiction.”Florida Building Code 2007: Plumbing Code; Section 202Stormwater often the most overlooked part of RHSInexperienced designers don’t consider the cumulative flow rate (if 3 x 4” pipes going in, better have at least 6” pipe going out).Example: builder responsible for storm drainage. RWS left 6” pipe stubbed out from tanks for overflow of catchment off a 4000 sf roof. Builder connected with 3” pipe. Led to “geyser” and flood of neighbor’s low-lying pool. Pool damaged, popped out of ground, etc…
“Surface Water: Surface water accumulates mainly as a result of direct runoff from precipitation. Precipitation that does not seep into the ground or evaporate, flows over the ground surface and is classified as direct runoff…In some areas, a source of water is the rainfall intercepted by roof surfaces on homes, barns, and other buildings. Water from those surfaces can be collected and stored in tanks called cisterns.”Manual for Individual and Non-community Water Supply SystemsUnited States EPA, Office of WaterDocument: EPA 570/9-91-004In order for regulatory agencies to evaluate potability of water supplies, the EPA provides updated standards for drinking water contaminants (see: http://www.epa.gov/safewater/standards.html). Treatment methods must meet or exceed the values specified by these standards.
Also cost will become more relevant as existing resources are depletedBackflow, testing, make-up supply, communicationEngineer is best friendNSF 53, NSF 55A, etcMake-up water controls. Not only level switched, also water quality switched.All involved from the beginning. All on same page throughout process.Still a lot of questions and misunderstanding. Need more education of all involved: - property owners - builders - engineers/architects (designers) - building officials - etc
Contact info, social networking feedsPresentation available to public on slideshare
Whole House Rainwater Harvesting: Capturing and Using Rainwater for Potable Applications
Whole House Rainwater Harvesting:<br />Capturing and Using Rainwater for Potable Applications<br />Brian Gregson<br />Rainwater Catchment Systems Accredited Professional<br />Photo credit:<br />REAL Building Group LLC<br />http://realbuilding.com<br />Conservation Coordination Consortium<br />Tampa Bay Water <br />October 13, 2010<br />
Who we are<br />Irrigation Contractor<br />Specializing in highly efficient water-conservation solutions<br />Drip/micro irrigation, landscape drainage<br />RAINWATER HARVESTING<br />FIRSTS:<br />ARCSA AP in State of FL<br />Permitted RHS in St. Pete<br />Institutional rainwater toilet flushing in St. Pete<br />Potable RHS in St. Pete<br />Potable RHS in Tampa<br />Permitted greywater(??) in Tampa<br />Shifting focus to commercial applications<br />www.rainwaterservices.com<br />
Why harvest rainwater?<br />Preserve potable water for drinking and indoor uses<br />Stormwater management<br />L.I.D.<br />Contribute to responsible growth<br />Larger volume = $$$$<br />www.rainwaterservices.com<br />
The PROBLEM:<br />Population growth = greater demand on resources (power, water, etc)<br />Reduced reliance on groundwater/surface water<br />Sinkholes??<br />Pollution??<br />Greater reliance on “innovative” water supplies (e.g. desalination)<br />RHS reduces demand on blended resources<br />www.rainwaterservices.com<br />
Possible Uses for Rainwater<br />Irrigation<br />Other Outdoor<br />Vehicle washing<br />Fountains<br />Swimming pool makeup<br />Industrial<br />Industrial processes instead of municipally treated water <br />Cooling tower makeup<br />Indoor<br />Toilet flushing<br />Potable<br />Drinking<br />Laundry<br />www.rainwaterservices.com<br />DISCUSSION SEED:<br />Ease watering restrictions when RHS used for the above??<br />
System Anatomy<br />Rain<br />The ON button!<br />Catchment Area<br />(roof)<br />Conveyance<br />(gutters/downspouts)<br />Pretreatment<br />(screen filters, first-flush)<br />Storage<br />(cistern)<br />Treatment & Distribution<br />Source: Harvesting Water for Landscape Use by Patricia H. Waterfall, p. 34 Original diagram was modified for this application.<br />www.rainwaterservices.com<br />
Catchment<br />Roof acts as the catchment area<br />Size <br />Determines harvesting potential<br />Surface material<br />Determines quality<br />The slicker, the better<br />For potable, metal is preferred<br />www.rainwaterservices.com<br />Courtesy: ARCSA<br />
Conveyance & Pretreatment<br />Water quality is determined by what is conveyed into the storage tank(s)<br />Roof surface debris<br />Twigs and leaves<br />Dust<br />Bird droppings<br />Other debris<br />www.rainwaterservices.com<br />
Conveyance & Pre-treatment<br />Leaf Guards<br />First line of defense<br />Screened rain heads<br />Finer, pre-tank protection<br />http://www.piroofing.com/clientimages/41860/gutter_anim_arrows.gif<br />http://9p-enterprises.com/LSpics.aspx<br />www.rainwaterservices.com<br />
First Flush Devices<br />Prevents initial volume (“first-flush”) of roof runoff from entering storage tanks.<br />After a rainfall event, the “dirty” water is released through a slow-release valve, to reset for the next rainfall.<br />10-50 gallons per 1000 sf roof area<br />www.rainwaterservices.com<br />http://www.rainharvesting.com/<br />
Cistern Anatomy<br />Lid or manway<br />Secured tightly to avoid entrance by children and animals.<br />Vent<br />Use fine mesh screen to keep mosquitoes out<br />Overflow<br />Inlet<br />Max Water Level<br />Use flap valve or other methods to keep insects and animals out<br />From downspouts<br />Turbulence calming device (optional)<br />To prevent remixing of sediment<br />Storage<br />Floating Suction Filter<br />(cistern)<br />Outlet<br />Tank Pad<br />To distribution<br />Source: Rainwater Harvesting Planning and Installation Manual, January 2009, Figure 12.5. Original diagram was modified for this application.<br />Anaerobic / Sediment<br />Hose Bibb<br />pacia<br />www.rainwaterservices.com<br />
Distribution<br />Select appropriate pump/pressure tank for water demand<br />Connect to disinfected indoor supply and/or irrigation system<br />Makeup water supply (if available) for low-water and/or poor water quality conditions<br />Backflow prevention!!!<br />Backflow prevention!!!<br />www.rainwaterservices.com<br />
Major Distribution Components:RELIABILITY<br />www.rainwaterservices.com<br /><ul><li>Pump
Regulatory Considerations:ENGINEERING<br />Plumbing<br />Makeup water controls<br />Treatment<br />Backflow prevention<br />Civil<br />Stormwater drainage<br />Electrical<br />Makeup water controls<br />Distribution/treatment components<br />RHS is relatively new/misunderstood. Few guidelines/codes/laws exist. Those that do aren’t necessarily clear. To ensure all building codes and building department concerns are met, <br />MUST HAVE QUALITY ENGINEERING!<br />www.rainwaterservices.com<br />
Regulatory Considerations:BUILDING CODES<br />Classification of rainwater leads to confusion<br />IPC does not directly address rainwater, which leads to confusion and misunderstanding<br />Too often, rainwater is considered as “graywater” for lack of a better definition<br />Graywater = “waste discharged from lavatories, bathtubs, showers, clothes washers, and laundry trays.” (IPC 2006; Appendix C: C101.9)<br />Rainwater is not graywater!!<br />Rainwater IS surface water<br />Surface water is suitable water supply (Florida Building Code 2007: Plumbing Code; Section 202)<br />Stormwater drainage<br />Too often overlooked/afterthought<br />Vertical and horizontal leaders must be sized appropriately (FBC 2007: Plumbing Code; Section 1106)<br />Tampa Bay 100 year rainfall event = 5” <br />What flows into tanks must flow out at same rate<br />All downspouts lead to a common point. Total flow rate is cumulative.<br />When in doubt, scale up the overflow<br />www.rainwaterservices.com<br />
Regulatory Considerations:HEALTH DEPARTMENTS<br />Classification:<br />Surface water private water supplies<br />For private water supplies, no state code requiring water quality sampling exists<br />However, recommended to test with same frequency as public well and/or surface water systems<br />Rainwater Services tests new potable systems for bacteria, lead and nitrates upon installation and as needed thereafter <br />www.rainwaterservices.com<br />
Regulatory Consideration:EPA<br />Defines surface water<br />Rainwater harvested in cisterns falls under the surface water definition<br /> Manual for Individual and Non-community Water Supply Systems<br /> United States EPA, Office of Water<br />Provides standards for drinking water contaminants<br />http://www.epa.gov/safewater/standards.html<br />www.rainwaterservices.com<br />
Summary<br />Harvested rainwater is a viable and practical water supply<br />For potable applications, strict attention must be paid to health, reliability & regulatory concerns<br />An effective system begins with proper design<br />Finished product must meet recognized standards for potability<br />Fail-safe reliability (redundancy) must be considered<br />Design and construction is a collaborative effort involving various trades, engineers and building officials<br />Education is key to widespread adoption of rainwater harvesting codes, regulation and guidelines<br />www.rainwaterservices.com<br />
Many thanks…<br />www.rainwaterservices.com<br />