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Line 7: − + − + − + − + − * Can be used throughout the year if they are located underground or indoors to prevent problems associated with freezing.+ − * Separate plumbing, pumps, pressure tanks, and backflow preventers are necessary for indoor use of harvested water. − * Back-up water supply system arrangements, that can be drawn upon when the cistern runs dry , are also necessary for indoor uses. − * Storage tanks in low elevated areas will increase volume of rainwater stored, but will increase the amount of pumping needed to distribute water. − * The opposite occurs for placing tanks at higher elevations. − * Cisterns should be placed on or in native, rather than fill, soils. − * Underground tanks and piping to and from cisterns should either be located below the local frost penetration depth or insulated to prevent freezing. − * An [[underdrain]] (minimum 200 mm perforated pipe) is only needed when native soil infiltration is less than 15 mm/hr or infiltration is precluded. − * [[Overflow]] devices should be designed to avoid causing ponding or soil saturation within 3 metres of building foundations. − * Tanks must be watertight to prevent water damage when placed near building foundations. − * [[Pretreatment]] is needed to remove debris, dust, leaves, and other debris that accumulates on roofs and can cause clogging within the RWH system.
Rainwater Harvesting & Cisterns: Life Cycle Costs (view source)
Revision as of 19:18, 10 January 2023
, 1 year ago→Design Assumptions
==Design Assumptions==
==Design Assumptions==
[[Rainwater harvesting|Rainwater harvesting (RWH)]] is ideal for sites that cannot infiltrate water (e.g. contaminated soils, WHPAs, IPZs, etc.), zero-lot-line developments, extensive gardens and landscapes. Components include: catchment area (e.g. rooftop), filter to remove coarse debris, cistern storage, and a connecting pipe network. Additional components include pumps to lift water to higher elevations, additional water filtration and treatment. <br>
[[Rainwater harvesting|Rainwater harvesting (RWH)]] is ideal for sites that cannot infiltrate water (e.g. contaminated soils, WHPAs, IPZs, etc.), zero-lot-line developments, large gardens and landscaped areas. Components include: catchment area (e.g. rooftop), filter to remove coarse debris, cistern storage, and a connecting pipe network. Additional components include pumps to lift water to higher elevations, additional water filtration and treatment. <br>
Design and operation and maintenance program assumptions used to generate cost estimates are based on tool default values and the following STEP recommendations:
Design and operation and maintenance program assumptions used to generate the cost estimate are based on tool default values and the following STEP recommendations:
* Native soil infiltration rates for Full, Partial and No Infiltration Design scenarios were assumed to be 20 mm/h, 10 mm/h and 2 mm/h, respectively, and a safety factor of 2.5 was applied to calculate the design infiltration rate.
* Total daily water use of 2,000 L per day (tool default).
* Operation and maintenance (O&M) cost estimates assume annual inspections, removal of trash and debris twice a year, removal of sediment from pretreatment structures annually, and removal of weeds twice a year (where applicable). Verification inspections are included every 5 years to confirm adequate maintenance, and every 15 years to confirm adequate drainage performance through in-situ surface infiltration rate testing (where applicable)
* User specified storage tank capacity of 50,000 L.
* Operation and maintenance (O&M) cost estimates assume annual inspections and cistern pump tests, removal of trash and debris from rooftop and pretreatment filter four times a year, and cleaning of cistern and replacement of pump and pressure tank every five years. Verification inspections are included every 5 years to confirm adequate maintenance.
===Notes===
===Notes===