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Rainwater harvesting (view source)

Revision as of 18:58, 10 March 2023

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[[File:STEP Minto Cistern P1 - Copy.jpg|thumb|Rainwater harvesting is commonly employed on zero-lot-line projects like downtown condos. This cast in place concrete vault in one corner of the parking level is a typical design.]]
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This article is about large, building-integrated rainwater harvesting systems. For smaller, seasonal, outdoor systems, see [[Rain barrels]]   
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[[File:STEP Minto Cistern P1 - Copy.jpg|thumb|500px|Rainwater harvesting is commonly employed on zero-lot-line projects like downtown condos. This cast in place concrete vault in one corner of the parking level is a typical design.]]
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This article is about large, building-integrated rainwater harvesting systems featuring underground or indoor cisterns or tanks and intended for year-round use. For smaller, outdoor systems intended for use during the growing season only, see [[Rain barrels]].  
 
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==Overview==
 
==Overview==
 
Rainwater harvesting (RWH) is the ancient practice of collecting and storing precipitation for later use. Although Ontario is a region with relatively abundant fresh water, RWH is increasing in popularity for a number of reasons:
 
Rainwater harvesting (RWH) is the ancient practice of collecting and storing precipitation for later use. Although Ontario is a region with relatively abundant fresh water, RWH is increasing in popularity for a number of reasons:
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The origin of the harvested water affects the permissible end uses. Some of the most common uses include irrigation and flushing or toilets and urinals. As mixed source water can only be applied to the more limited end uses, selecting the catchments for a RWH system requires careful consideration.
 
The origin of the harvested water affects the permissible end uses. Some of the most common uses include irrigation and flushing or toilets and urinals. As mixed source water can only be applied to the more limited end uses, selecting the catchments for a RWH system requires careful consideration.
 
*The [https://www.ontario.ca/laws/regulation/120332 Ontario Building Code (OBC)] regulates the use of harvested rainwater as one of many non-potable water sources. <em>"Rainwater means storm sewage runoff that is collected from a roof or the ground, but not from accessible patios and driveways."</em>
 
*The [https://www.ontario.ca/laws/regulation/120332 Ontario Building Code (OBC)] regulates the use of harvested rainwater as one of many non-potable water sources. <em>"Rainwater means storm sewage runoff that is collected from a roof or the ground, but not from accessible patios and driveways."</em>
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*The [https://store.csagroup.org/?cclcl=en_US| CSA standard B805-18/ICC805-2018] separates <em>"roof runoff"</em> from all other sources, including landscaped areas and green roofs. Collectively green roofs, landscaped and paved areas result in <em>"stormwater runoff."</em>   
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*The [https://www.csagroup.org/store CSA standard B805-18/ICC805-2018] separates <em>"roof runoff"</em> from all other sources, including landscaped areas and green roofs. Collectively green roofs, landscaped and paved areas result in <em>"stormwater runoff."</em>   
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The current disparity between these two definitions affects all vegetated landscapes including green roofs. Confusion over terminology and regulation has been identified as a significant barrier to implementation of RWH since 2010[http://www.ryerson.ca/content/dam/water/education%20and%20outreach/GreenInfraTO/Identifying%20Barriers%20to%20Widespread%20Implementation%20of%20Rainwater%20Harvesting%20for%20Urban%20Household%20Use%20in%20Ontario.pdf].
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The current disparity between these two definitions affects all vegetated landscapes including green roofs. Confusion over terminology and regulation has been identified as a significant barrier to implementation of RWH in Ontario since 2010 <ref> Leidl, C., Farahbakhsh, K., FitzGibbon, J. 2010. Identifying Barriers to Widespread Implementation of Rainwater Harvesting for Urban Household Use in Ontario. Canadian Water Resources Journal. Vol. 35 (1): 93-104. https://www.tandfonline.com/doi/pdf/10.4296/cwrj3501093 </ref>].
    
===Cistern and Pipework===
 
===Cistern and Pipework===
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#The entire system is drained and closed off ahead of [[sub-zero temperatures]]
 
#The entire system is drained and closed off ahead of [[sub-zero temperatures]]
 
#All pipework, pumps, filters and the cistern are protected from freezing during the winter
 
#All pipework, pumps, filters and the cistern are protected from freezing during the winter
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The first option may be suitable for systems optimized for exterior irrigation only. But regulatory authorities may not permit the use of such seasonal systems as part of a storm water control strategy. Year round systems can be protected from freezing by locating the pipes, pumps and cistern indoors and/or below the frost penetration depth[http://www.raqsb.mto.gov.on.ca/techpubs/ops.nsf/0/ee1f1756eacc00e18525808200628fbf/$FILE/OPSD3090.101%20Rev%231%20Nov2010.pdf].  
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The first option may be suitable for systems optimized for exterior irrigation only. But regulatory authorities may not permit the use of such seasonal systems as part of a storm water control strategy. Year round systems can be protected from freezing by locating the pipes, pumps and cistern indoors and/or below the frost penetration depth[http://www.raqsb.mto.gov.on.ca/techpubs/ops.nsf/0/ee1f1756eacc00e18525808200628fbf/$FILE/OPSD3090.101%20Rev%231%20Nov2010.pdf].
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===Design for Maintenance===
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<br>
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==Inspection and Maintenance==
 
Detailed inspection and maintenance advice can be found in [http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2016/08/LID-IM-Guide-7.7-Rainwater-Cisterns.pdf Sustainable Technologies' LID I&M guide].  
 
Detailed inspection and maintenance advice can be found in [http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2016/08/LID-IM-Guide-7.7-Rainwater-Cisterns.pdf Sustainable Technologies' LID I&M guide].  
 
The two primary operational concerns for RWH systems are:
 
The two primary operational concerns for RWH systems are:
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*Is the roof (catchment) readily accessible to sweep debris periodically?
 
*Is the roof (catchment) readily accessible to sweep debris periodically?
 
*Could the accumulation of debris on the roof be reduced by removing any overhanging branches?  
 
*Could the accumulation of debris on the roof be reduced by removing any overhanging branches?  
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*Can the leaf screens accessed from the roof? Or from a maintenance room?
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*Can the leaf screens be accessed from the roof? Or from a maintenance room?
 
*Will the cistern require entry for inspection in the future? How will this be accessed?
 
*Will the cistern require entry for inspection in the future? How will this be accessed?
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''RWH systems producing higher quality water will have additional maintenance requirements. These will depend on the the treatment technologies being used.''
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''RWH systems producing higher quality water will have additional maintenance requirements. These will depend on the the treatment technologies being used.''<br>
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</br>
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Take a look at the [[Inspection and Maintenance: Rainwater Harvesting]] page by clicking below for further details about proper inspection and maintenance practices:
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{{Clickable button|[[File:Rainwater cistern opening title.PNG|200 px|link=https://wiki.sustainabletechnologies.ca/wiki/Inspection_and_Maintenance:_Rainwater_Harvesting]]}}
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[[File:RAINWATER HARVESTING TANK 550x550.jpg|thumb|Large cistern being installed underground]]
 
[[File:RAINWATER HARVESTING TANK 550x550.jpg|thumb|Large cistern being installed underground]]
 
[[File:RWH Tree.PNG|thumb|Conceptual image of an underground cistern being used for irrigation of nearby vegetation on site.]]
 
[[File:RWH Tree.PNG|thumb|Conceptual image of an underground cistern being used for irrigation of nearby vegetation on site.]]
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In a recent international research literature review on urban rainwater harvesting systems, Campisano et al. (2017) note that degree of implementation and design choices are strongly influenced by economic constraints (need for low cost, easy to retrofit systems) and government regulations (need for policies, standards and guidelines that ensure system efficacy and improve community acceptance), and that systems tend to be designed for water conservation alone, without considering co-benefits like helping to achieve stormwater management objectives. <ref> Campisano, A., Butler, D., Ward, S., Burns, M.J., Friedler, E., DeBusk, K., Fisher-Jeffes, L.N., Ghisi, E., Rahman, A., Furumai, H., Han, M. 2017. Urban rainwater harvesting systems: Research, implementation and future perspectives. Water Research. 115 (2017) 195-209. https://www.sciencedirect.com/science/article/abs/pii/S0043135417301483?via%3Dihub </ref>  Adequately sizing rainwater harvesting systems is critical to optimizing their operation because under-sizing results in systems that are unable to provide sufficient, reliable sources of water while oversizing increases the capital costs incurred and poses potential water quality risks if stored water remains unused for long periods of time. In a recent research literature review, Semaan et al. (2020) identified sizing for water storage as most important for system optimization, yet found that sizing for cost is a more frequently implemented optimization approach. They note several sizing and optimization approaches and tools are available globally. <ref>Semaan, M., Day, S.D., Garvin, M., Ramakrishnan, N., Pearce, A. 2020. Optimal sizing of rainwater harvesting systems for domestic water usages: A systematic literature review. Resources, Conservation & Recycling: X 6 (2020) 100033. https://www.sciencedirect.com/science/article/pii/S2590289X20300049?via%3Dihub </ref>   
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Follow the link below for detailed guidance on approaches to sizing rainwater harvesting systems in Ontario. <br>
 
[[Rainwater Harvesting: Sizing and Modelling]]
 
[[Rainwater Harvesting: Sizing and Modelling]]
 
===Catchments===
 
===Catchments===
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The current Ontario Building Code requires that rainwater harvesting systems are designed, constructed and installed to conform to good engineering practice. References are made to ASHRAE, ASPE[https://www.aspe.org/content/arcsaaspeansi-63-2013-rainwater-catchment-systems-electronic-download]  and CSA  [http://shop.csa.ca/en/canada/plumbing-products-and-materials/cancsa-b1281-06b1282-06-r2016/invt/27024892006] guides for plumbing detailing.
 
The current Ontario Building Code requires that rainwater harvesting systems are designed, constructed and installed to conform to good engineering practice. References are made to ASHRAE, ASPE[https://www.aspe.org/content/arcsaaspeansi-63-2013-rainwater-catchment-systems-electronic-download]  and CSA  [http://shop.csa.ca/en/canada/plumbing-products-and-materials/cancsa-b1281-06b1282-06-r2016/invt/27024892006] guides for plumbing detailing.
 
These guides focus on ensuring that the rainwater does not contaminate or become mistaken for the municipal drinking water supply. Similarly, rainwater must be prevented from becoming contaminated from the sewer. In both cases, an air gap or a back-flow preventer is required.
 
These guides focus on ensuring that the rainwater does not contaminate or become mistaken for the municipal drinking water supply. Similarly, rainwater must be prevented from becoming contaminated from the sewer. In both cases, an air gap or a back-flow preventer is required.
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==Construction==
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===Construction Considerations===
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For installation of a cistern (either residentially or commercially), it is advisable to have an experienced contractor who is familiar with appropriate cistern sizing, experience using the chosen installation materials, and knowledge of proper site placement to ensure appropriate use and performance of the feature long-term. A minimum one-year warranty is recommended.
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===Construction Inspection===
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The following items should be inspected prior to final sign-off on the stormwater management construction:
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• Catchment area matches original design plans;
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• [[Overflow|Overflow system]] is properly sized and installed;
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• [[Pretreatment]] system is installed;
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• Screens are installed on all openings;
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• Cistern foundation is constructed as shown on original design plans; and
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• Catchment area and overflow area are properly stabilized.
    
==Performance==
 
==Performance==
 
<h3>Water Quantity</h3>
 
<h3>Water Quantity</h3>
 
In theory a large enough RWH cistern could retain 100% of a single storm. However, sizing a stormwater cistern must account for regulatory requirements, available space, budget, and draw-down i.e. rate of use. If a RWH system is being employed for storm water control, the cistern size will typically be greater than that for optimized potable water use reduction.<br>
 
In theory a large enough RWH cistern could retain 100% of a single storm. However, sizing a stormwater cistern must account for regulatory requirements, available space, budget, and draw-down i.e. rate of use. If a RWH system is being employed for storm water control, the cistern size will typically be greater than that for optimized potable water use reduction.<br>
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In 2007-2010 STEP monitored and modelled three rainwater harvesting systems in the Greater Toronto Area[http://www.sustainabletechnologies.ca/wp/home/urban-runoff-green-infrastructure/low-impact-development/rainwater-harvesting/performance-evaluation-of-rainwater-harvesting-systems-toronto-ontario/]. Each system was sized  to balance stormwater management objectives with with potable water use reduction for irrigation and toilet flushing. Around 18-20% of the precipitation was lost directly from the rooftop, and the annual stormwater capture varied between 18 and 42 %.
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<br>
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In 2007-2010 STEP monitored and modelled three rainwater harvesting systems in the Greater Toronto Area[http://www.sustainabletechnologies.ca/wp/home/urban-runoff-green-infrastructure/low-impact-development/rainwater-harvesting/performance-evaluation-of-rainwater-harvesting-systems-toronto-ontario/]. Each system was sized  to balance stormwater management objectives with with potable water use reduction for irrigation and toilet flushing. Around 18-20% of the precipitation was lost directly from the rooftop, and the annual stormwater capture varied between 18 and 42%.
 
<h3>Water Quality</h3>
 
<h3>Water Quality</h3>
 
{{:Rainwater_harvesting:_Water_quality}}
 
{{:Rainwater_harvesting:_Water_quality}}
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==Life Cycle Costs==
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To learn about Life Cycle Costs associated with this practice (i.e. Pre-construction, Excavation, Materials & Installation, Project Management, Overhead, Inspection and Maintenance, Rehabilitation and other associated costs), visit the [[Rainwater Harvesting & Cisterns: Life Cycle Costs]] page to view a cost estimate for a 50,000 L, below-ground concrete cistern.  Alternatively you can use the [https://sustainabletechnologies.ca/lid-lcct/ STEP's Low Impact Development Life Cycle Costing Tool (LID LCCT)] to generate cost estimates customized to your own LID stormwater design project specifications.
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Take a look at the [[Rainwater Harvesting & Cisterns: Life Cycle Costs]] page by clicking below for further details:
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{{Clickable button|[[File:Construction Breakdown RWH No Infil.PNG|125 px|link=https://wiki.sustainabletechnologies.ca/wiki/Rainwater_Harvesting_%26_Cisterns:_Life_Cycle_Costs]]}}
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==Incentives and Credits==
 
==Incentives and Credits==
 
<h3>In Ontario</h3>
 
<h3>In Ontario</h3>
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*[[Rain Barrels|Rain Barrels]]
 
*[[Rain Barrels|Rain Barrels]]
 
==External Links==
 
==External Links==
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===Rainwater harvesting system design guides===
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*[https://www.csagroup.org/store Canadian Standards Association (CSA) B805-18/ICC805-2018, Rainwater harvesting systems]
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*[https://www.crd.bc.ca/docs/default-source/water-pdf/cmhcrainwaterhandbook.pdf?sfvrsn=67aa96c9_2 CMHC Guidelines for Residential Rainwater Harvesting Systems Handbook (2012)]
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*[http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2013/02/ONTARIO_RWH_GUIDELINES_2010.pdf Ontario Rainwater Harvesting Guidelines (2010)]
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===Organizations===
 
===Organizations===
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*[http://www.canarm.org/ CANARM]
   
*[http://www.harvesth2o.com/about.shtml HarvestH2O]
 
*[http://www.harvesth2o.com/about.shtml HarvestH2O]
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===RWH Design guides===
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*[https://rainbarrel.ca/ RainBarrel.ca]
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*[https://www.cmhc-schl.gc.ca/odpub/pdf/67608.pdf Guidelines for Residential Rainwater Harvesting Systems Handbook]
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*[https://rainwatercollectionsupply.ca/ Rainwater Collection Supply Canada]
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*[http://www.sustainabletechnologies.ca/wp/wp-content/uploads/2013/02/ONTARIO_RWH_GUIDELINES_2010.pdf Ontario Rainwater Harvesting Guidelines]
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===Proprietary systems===  
 
===Proprietary systems===  
 
{{:Disclaimer}}
 
{{:Disclaimer}}
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*[http://greyter.com/ Greyter]
 
*[http://greyter.com/ Greyter]
 
*[http://www.interpump.ca/ Interpump]
 
*[http://www.interpump.ca/ Interpump]
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*[https://www.makeway.ca/products/rainwater-harvesting-systems/ Make-Way Environmental Technologies Inc.]
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*[https://www.premiertechaqua.com/en-ca/water-management/rainwater-harvester PremierTech REWATEC]
 
*[http://rh2o.com/company RH<sub>2</sub>O]
 
*[http://rh2o.com/company RH<sub>2</sub>O]
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*[http://waterloo-biofilter.com/rainwater-harvesting/ Waterloo Biofilter]
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*[https://www.makeway.ca/ Make-Way Environmental Technologies Inc.]
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==References==
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