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Inspection and Maintenance: Rainwater Harvesting (view source)
Revision as of 20:11, 16 August 2022
, 1 year agono edit summary
*Provide a means of draining the [[Rainwater harvesting: Sizing and modeling#Cistern dimensions|cistern]] by gravity to make [[inspection and maintenance]] work that requires drainage of the BMP easier to perform.
*Provide a means of draining the [[Rainwater harvesting: Sizing and modeling#Cistern dimensions|cistern]] by gravity to make [[inspection and maintenance]] work that requires drainage of the BMP easier to perform.
*Remove accumulated sediment from a large [[Rainwater harvesting: Sizing and modeling#Cistern dimensions|cistern]] using a pressure washer or hydro-vac truck equipped with a JetVac nozzle to scour and direct sediment to a collection point for removal by vacuuming; for small cisterns, a garden hose and wet shop vacuum may be used.
*Remove accumulated sediment from a large [[Rainwater harvesting: Sizing and modeling#Cistern dimensions|cistern]] using a pressure washer or hydro-vac truck equipped with a JetVac nozzle to scour and direct sediment to a collection point for removal by vacuuming; for small cisterns, a garden hose and wet shop vacuum may be used.
==Rehabilitation & Repair==
Table below provides guidance on rehabilitation and repair work specific to rainwater harvesting systems and rain barrels organized according to BMP component. For more detailed guidance on troubleshooting rainwater
harvesting systems refer to [https://www.harvesth2o.com/adobe_files/ONTARIO_RWH_HANDBOOK_2010.pdf Ontario Guidelines for Residential Rainwater Harvesting Systems - Handbook] (Despins, 2010)<ref>Despins. 2010. Ontario Guidelines for Residential Rainwater Harvesting Systems - Handbook. Accessed August 15, 2022. https://www.harvesth2o.com/adobe_files/ONTARIO_RWH_HANDBOOK_2010.pdf</ref> and the [https://www.crd.bc.ca/docs/default-source/water-pdf/cmhcrainwaterhandbook.pdf?sfvrsn=67aa96c9_2 Canadian Guidelines for Residential Rainwater Harvesting Systems Handbook], developed by the Canadian Mortgage and Housing Corporation (CHMC) (Despins, 2012)<ref> Despins. 2012. Canadian Guidelines for Residential Rainwater Harvesting Systems Handbook. Accessed August 15, 2022. https://www.crd.bc.ca/docs/default-source/water-pdf/cmhcrainwaterhandbook.pdf?sfvrsn=67aa96c9_2.</ref>
[[File:Cleanign cistern tank.jpg|405px|thumb|Technician conducting FIT work to ensure cistern tank is in optimal working order. (Photo Source: Pristine Water Systems, 2017)<ref>Pristine Water Systems. 2017. When is the best time to clean my Rainwater Tank? Accessed 16 August 2022. https://www.pristinewatersystems.com.au/2017/02/20/best-time-to-clean-rainwater-tank/</ref>]]
{|{| class="wikitable" style="width: 800px;"
|+'''Rainwater Harvesting Systems: Key Components, Typical Issues and Rehabilitation Requirements'''
|-
!Component
!Problem
!Rehabilitation Tasks
|-
|rowspan="2"|'''[[Inlets]]'''
|
Pipes or fittings are damaged or displaced.
|
*Schedule repairs.
|-
|Ice is accumulating and obstructing inflow to BMP.
|
*Schedule installation of heat trace wire along eavestroughs, around roof drains and in aboveground [[pipes]], or disconnect the system during [[winter]].
|-
|rowspan="2"|'''[[Rainwater harvesting: Sizing and modeling#Cistern dimensions|Cistern]]'''
|
Cracks are visible or seals between joints in the structure are leaking.
|
*Schedule repairs with oversight by the product manufacturer/vendor.
|-
|Cistern has reached 40 years of age and is due for replacement.
|
*Replace cistern with new one that meets design specifications.
|-
|'''[[Overflow|Overflow Outlet]]'''
|
Overflow outlet pipe is obstructed by trash, debris or sediment.
|
*Schedule drain snaking service or pressure/vacuum truck to remove the obstruction.
|-
|'''Make-up water supply'''
|
System is malfunctioning (e.g., tops up cistern water level when unnecessary or fails to top up when needed).
|
*Schedule FIT work to determine the cause of system malfunction with oversight by the product manufacturer/vendor or a licensed plumber and electrician.
|-
|'''[[Rainwater harvesting: Sizing and modeling#Cistern dimensions|Pump]]'''
|
Pump is not delivering water to fixtures or not providing adequate water pressure.
|
*Schedule FIT work to determine the cause of system malfunction with oversight by the product manufacturer/vendor or a licensed plumber and electrician.
|-
|}
==Inspection Time Commitments and Costs==
Life cycle cost estimates are based on two design variations that can be used year-round: underground concrete cistern; and indoor plastic cistern systems. For each design variation, life cycle costs can be found in the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-7.7-Rainwater-Cisterns.pdf Low Impact Development (LID) Stormwater Management Practice Inspection and Maintenance Guide]<br>
</br>
[[File:Time commit costs RWH.PNG|thumb|left|400px|General time commitments and costs for inspection of rainwater harvesting features features with partial infiltration (in 2016 $ figures) (TRCA, 2018)<ref name="example1" />.]]
[[File:Costs per maintenance task RWH.PNG|thumb|400px|Per-task cost estimates for maintenance and rehabilitation of rainwater harvesting features features with partial infiltration (in 2016 $ figures) (TRCA, 2018)<ref name="example1" />.]]
[[File:Life cycle costs RWH.PNG|thumb|center|400px|Construction and life cycle cost estimates for rainwater harvesting features features with partial infiltration (in 2016 $ figures) (TRCA, 2018)<ref name="example1" />.]]<br>
Estimates of the life cycle costs of inspection and maintenance have been produced using the latest version of the [[Cost analysis resources|LID Life Cycle Costing Tool]] for two design variations (underground concrete cistern; and indoor plastic cistern systems) to assist stormwater infrastructure planners, designers and asset managers with planning and preparing budgets for potential LID features.
Assumptions for the above costs and the following table below are based on the following:
*For rainwater cisterns it is assumed that no rehabilitation work will be needed to maintain acceptable storage and drainage performance over a 50 year period of operation (40 for plastic cisterns), given that pretreatment devices are in place and are being adequately maintained. The annual average maintenance cost value represents an average of routine maintenance tasks, as outlined in Rainwater Harvesting: Key Components, Descriptions and Routine I&M Requirements table above. All cost value estimates represent the NPV as the calculation takes into account average annual interest (2%) and discount (3%) rates over the evaluation time periods.
*Life cycle cost estimates have been generated for two design variations that can be used year-round: underground concrete cistern; and indoor plastic cistern systems. For each design variation, life cycle cost estimates have been calculated for two level-of-service scenarios: the minimum recommended frequency of inspection and maintenance tasks in the Per-task cost estimates for maintenance and rehabilitation of rainwater harvesting features table above to provide an indication of the potential range. Only the indoor plastic cistern requires rehabilitation within the 50 year evaluation period. At year 40 it is assumed the plastic cistern is replaced with anew one.
*For all scenarios, the roof area that drains into the rainwater harvesting cistern is 2,000 m<sup>2</sup>. The water storage capacity of the cistern is assumed to be 23,000 L. Both cistern systems include a dual plumbing distribution system, an 81.2 LPM submersible pump and a 439 L expansion tank. The systems also include a float switch to prevent the pump from dry running, a top-up float switch and associated wring, a solenoid valve, air gap to prevent backflow, as well as backflow preventer at the premise boundary, a water meter and a water hammer arrestor. The rainwater is used for toilet flushing of 260 occupants. It is assumed that two hose bibs are used on average 14 minutes per day from April to September. The underground concrete cistern is installed adjacent to the building. The plastic cistern is stored inside the building, so no excavation is required to install/uninstall it.
*Estimates of the life cycle costs for the two rainwater cistern system design variations in Canadian dollars per unit CDA ($/m<sup>2</sup>) are presented in the table below. The LID Life Cycle Costing Tool allows users to select what BMP type and design variation applies, and to use the default assumptions to generate planning level cost estimates. Users can also input their own values relating to a site or area, design, unit costs, and inspection and maintenance task frequencies to generate customized cost estimates, specific to a certain project, context or stormwater infrastructure program.
*For indoor plastic cistern systems it is assumed that replacement of the cistern itself is needed once it reaches 40 years of age. Replacement of the cistern is assumed to typically involve the following tasks and associated costs:
**Dismantle all portions of the system within or connected to the cistern;
**Replace the plastic cistern with a new one that meets design specifications;
**Reassemble the system, re-using existing components;
**Construction and Assumption inspection work associated with the rehabilitation work (including cistern pump testing). <br>
</br>
[[File:Life cycle cost all variations RWH.PNG|thumb|center|900px|Life cycle cost estimates for both underground (buried) concrete cisterns and indoor plastic cisterns under minimum and high frequency scenarios (in 2016 $ figures)<ref name="example1" />.]]
'''Notes:'''
<small>
#Estimated life cycle costs represent NPV of associated costs in Canadian dollars per squaremetre of CDA ($/m<sup>2</sup>).
#Average annual maintenance cost estimates represent NPV of all costs incurred over the time period and do not include rehabilitation costs.
#Over a 50 year evaluation period, average annual maintenance cost estimates for the High Frequency maintenance scenario are 59% and 56% higher than the Minimum Recommended Frequency maintenance scenario for underground concrete cistern and indoor plastic cistern systems respectively.
#Rehabilitation costs for the indoor plastic cistern system (i.e., replacing the cistern structure) are estimated to be 9.67% of the original construction costs, regardless of the maintenance frequency.
#Maintenance costs over a 25 year time period for underground concrete cistern systems are estimated to be 45.8% of the original construction cost for the Minimum Recommended Frequency maintenance scenario, and 89.4% for the High Frequency maintenance scenario.
#Maintenance costs over a 25 year time period for indoor plastic cistern systems are estimated to be 47.7% of the original construction cost for the Minimum Recommended Frequency maintenance scenario, and 98.0% for the High Frequency maintenance scenario.
#Maintenance costs over a 50 year time period for underground concrete cistern systems are estimated to be 0.918 times the original construction cost for the Minimum Recommended Frequency maintenance scenario, and 1.59 times for the High Frequency maintenance scenario.
#Maintenance costs over a 50 year time period for indoor plastic cistern systems are estimated to be 1.07 times the original construction cost for the Minimum Recommended Frequency maintenance scenario, and 1.84 times for the High Frequency maintenance scenario.
</small>
==Inspection Field Data Sheet==
Feel free to '''download''' (downward facing arrow on the top righthand side) and '''print''' (Pinter emoticon on top right hand side) the following Rainwater Cisterns/Harvesting Inspection Field Data Form developed by TRCA, STEP and its partners for the [https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide]<ref>STEP. 2016. Low Impact Development Stormwater Management Practice Inspection and Maintenance Guide. https://sustainabletechnologies.ca/app/uploads/2016/08/LID-IM-Guide-2016-1.pdf</ref>.
The 3 page document prompts users to fill out details previously mentioned above on this page in other sections about various zones associated with [[Rainwater harvesting]] systems and [[rain barrels]], along with other associated features (i.e. inlets, CDA, pretreatment, outlets, access hatches, etc.) and describe why each area is a pass or fail, and if remediate action is required and under what timeframe it would be completed by. Furthermore, the forms prompt the reviewer to determine what type of inspection is being conducted for the feature in question: Construction (C), Routine Operation (RO), Maintenance Verification (MV), or Performance Verification (PV). <br>
<br>
[[File:Access Hatch RWH.PNG|thumb|340px|An access hatch to help make inspecting and maintaining rainwater cisterns easier to do for technicians or hired professionals. (Photo Source: TRCA).]]
<pdf width="900" height="800">File:LID-IM-Guide-2016-1.pdf RWH.pdf</pdf>
==References==