B4: Green Water Supply Systems Flashcards
What is Rain Water Harvesting?
is the practice of collecting / storing rainwater for future use
Where does the water collect from?
roofs
Harvested rain water can be used for what?
toilet flushing and lawn irrigation (also urinals)
Other uses of rain water are not allowed unless.
Treated, inspected / certified
Harvested or recovered rainwater commonly refers to?
A type of auxiliary water supply that is collected from external surfaces of buildings or other hard-surfaced areas not exposed to vehicular or pedestrian traffic
What is water quality determined by?
Its microbiological, chemical
physical properties
What does physical properties include?
pH, colour, odour, turbidity and bacteria
Rainwater has the potential to harbour what types of organisms?
pathogenic
Who should you check with prior to installation / enquire about permits?
AHJ
What are the 3 benefits of RWH?
1) protecting / conserving water
2) reducing amount of storm water runoff
3) Reducing homeowners’ potable water use
True or False: roofs are the only surface permitted for residential rainwater collection
True
Why is collection from asphalt roofs not great?
dt its rough surfaces, tendency to slow down / evaporate surface water, particulates / other contaminates can dislodge
Are green roofs recommended for rainwater harvesting?
no
What style are most gutters?
5” K style aluminum or galvanized steel
What size are typical leaders?
2x3” or 3x3”
Where shouldn’t leaders be located?
Inside corners of walls or inside the building envelope (unless absolutley necessary)
What is a conveyance pipe?
a pipe that transports rainwater from leader to storage tank
What must be taken into consideration when conveyance pipe is located above ground?
above grade / sun exposure
What needs to be considered when designing / installing a conveyance network?
Sizing / placement
site conditions / location / placement of storage tank
What type of material is not recommended for gutters/leaders?
copper, wood, vinyl plastic
(rainwater can be acidic which can affect copper)
True or False: the greater the slope the better
true
What materials are used for storage tanks?
high-density polyethylene
fibreglass, steel, concrete / crate and bag
What are the benefits of the different storage tank materials?
Concrete = longevity / strength
Plastic / fibreglass = lightweight / strong
Steel = corrosion / aesthetics
crate - and-bag = light / strong (not normally used)
Tank sizing includes what?
rainwater load, number of toilets, irrigation, roof catchment area, local rainfall, potential growth, number of people in the house
What is collection effeiciency?
the % of rainfall landing on the roof that will find its way to the storage tank
What is the average collection effeciency?
75%
What are reasons for lost effeciency?
1) roof material, overhanging branches
2) collection system (overflow / spillage)
3) Seasonal factors
1 metre squared of catchment area x 1mm = how many L?
1L
What size of access hatch is needed?
24” or larger – allows entry
Does an overflow pipe need to be larger, smaller or the same size as inlet pipe?
Same size or larger
What is a calmed inlet?
conveyance pipe is brought near to the bottom w/o disturbing the sediment (is 90 degrees or U shaped)
What is dead space?
the 4-6” unused portion of rainwater at the bottom of the storage tank
What is the dead space’s job?
to ensure the submersible pump or suction line does not run dry
How often should rainwater tanks be inspected?
at least once a year
What are 2 ways treatment can be applied to improve rainwater quality?
Pre-storage tx
Post-storage tx
What are 3 methods of Pre-storage tx?
(For fuck sakes)
1) First flush diversion
2) Filtration
3) Settling
What is the First Flush diversion?
diverting the first portion of runoff away from the storage tank
What does filtration include?
Involves screening out leaves / large debris from runoff
Settling chamber, what is it?
A rainwater tank that has a separate chamber for debris to settle and water to con’t to the storage tank
What is Post-storage tx include?
(DTF)
1) filtration
2) disinfection
3) tx of aesthetic issues - colour, taste, odour
What is commonly used for disinfection?
UV and chlorine
Pre-storage tx devices should be inspected how often?
at least twice a year (or as per manufactures instructions)
How often should post-storage tx devices be inspected?
at least quarterly
What is the primary concern w/ a make up system?
requires a potable water source to be brought in close proximity w/ rainwater which creates a CC
What are 2 types of Make-up water systems?
1) top up - uses potable water to fill storage tank when needed
2) bypass
What are 2 areas of protection that the installation of backflow preventers address?
1) zone isolation
2) premise protection
What is a zone isolation?
backflow preventer is installed at the point of use
protects occupants in building
A zone isolation backflow preventer uses what for a rainwater storage system
air gap
Premises protection
uses an air gap?
What is the point of a pressure tank?
To prolong pump life
Pump selection involves what?
Pump location, controller, voltage
pump flow rate (l/sec or GPM)
pump system head (pressure)
What are the 3 components of total dynamic head
(FDS)
1) suction head
2) Discharge head
3) friction head
What is suction head?
the vertical distance or height that water must be lifted (pulled) before arriving at the pump.
only applies to Jet pump
What is Discharge head?
the vertical height from the pump –> the highest fixture
What is Friction head?
the loss in pressure resulting from water traveling through pipes / fittings
