Harvesting Rainwater. Kevin Johnson; CID, CIC, CLWM, CLIA, CGIA Director, National Sales Munro Companies

Transcription

1 Harvesting Rainwater Kevin Johnson; CID, CIC, CLWM, CLIA, CGIA Director, National Sales Munro Companies

2 Background Used since ancient times to capture and hold water for later use! Reduces consumption of potable water! Both large and small systems! Used for! Irrigation! Non potable purposes! Sometimes potable purposes!

3 ! What We Will Cover Today What is a RWH system?! Components of a RWH system! Common equipment and installation standards! How to calculate supply and demand system sizing!!

4 Advantages of RWH The water is free only cost for collection and use! The end use of the harvested water is close to the source no costly distribution systems! Provides a water source when ground water is unavailable or unacceptable can augment limited supplies! Superior quality water for landscape irrigation!!

5 Advantages of RWH Reduces flow to storm water drains and nonpoint source pollution! Helps water utilities reduce summer peak demand and delay expensive infrastructure expansion! Reduces consumers utility bills!

6 What is Rainwater? Rainwater is water that falls on a roof or other hard, impervious non-pedestrian, nonvehicular surface and is captured, filtered and stored.! Storm water is rainwater that has made contact with the ground, sidewalks, parking lots and other surfaces that can contribute contaminates.!

7 What is a Rainwater Harvesting System? Rainwater harvesting is the capture, diversion and storage of rainwater for a number of different purposes including, but not limited to, landscape irrigation.! Rainwater harvesting also includes landbased systems with man-made landscape features to channel and concentrate rainwater in either storage basins or planted areas.!

8 What is a Rainwater Harvesting System? Rainwater harvesting is practical only when the volume and frequency of rainfall and size of the catchment surface can generate sufficient water for the intended purpose.! Rainwater harvesting is best implemented in conjunction with other efficiency measures.! A rainwater harvesting system may also be used to capture condensate from commercial air conditioning systems.!

9 What is a Rainwater Harvesting System? Along with the independence of rainwater harvesting systems comes the inherent responsibility of operation and maintenance.!

10 Utah Rainwater Capture Law Utah allows for the direct capture and storage of rainwater on land owned or leased by the person responsible for the collection. According to Senate Bill 32 (2010), a person registered with the Division of Water Resources may collect and store no more than 2,500 gallons of rainwater. If unregistered, no more than two containers may be used, and the maximum storage capacity of any one container shall not be greater than 100 gallons (Utah Code Annotated ).!!

11 Passive Collection

12 Passive Collection

13 Passive Collection

14 Passive Collection

15 Passive Collection

16 Active Collection Components Catchment surface! Gutters and downspouts! Leaf screens, first flush diverters and roof washers! Storage tanks! Delivery system! Filtration!

17 Catchments Usually a roof! Texture makes a difference the smoother the better metal! Porous surfaces such as clay and concrete can contribute as much as a 10% loss due to texture, inefficient flow and evaporation.!

18 Catchments Composite shingle roofs are OK but are inefficient and add debris.! Wood, tar and gravel roofs are also inefficient and/or may contribute contaminants.!

19 Gutters Most common types will work half-round PVC, vinyl, seamless aluminum, galvanized! Copper may cause staining of porcelain fixtures! Size gutter to roof size to avoid over-running 5 wide is a good rule of thumb! Slope gutter toward downspout 1/16 per foot of gutter! Be aware of roof valleys that will increase flow!

20 Gutters The front of the gutter should be ½ lower than the back! Gutter hangers every three feet minimum!

21 Downspouts Space downspouts a minimum of 20, maximum of 50 apart! Provide 1 square inch of downspout area for every 100 square feet of roof area! Shape does not matter! Use 4 diam. Schedule 40 PVC to convey water to filter and cistern!

22 Gutter Filters Some type of leaf screen is necessary!

23 Gutter Filters ¼ wire mesh! Gutter Guard systems!

24 Gutter Filters Funnel-type downspout filter Basket filters

25 First Flush Diverters The first flush diverter routes the first flow of water away from the storage tank! Important to keep small debris and contaminants out of the system!

26 First Flush Diverters Rule of thumb divert a minimum of 10 gallons for every 1,000 sq. ft. of collection surface! Each downspout may need a first flush device if the roof area is large.!

27 Roof Washers The roof washer is placed just ahead of the storage tank and filters small debris to protect drip irrigation systems.! The filter is about 30 micron or 400 mesh and must be cleaned regularly.!

28 Smoothing Inlet Used to prevent the agitation of sediment at the rainwater inlet into the storage tank or cistern.!

29 Storage Tanks The most expensive component of the system! Generally plastic, fiberglass, concrete or metal! Must be opaque or installed below ground! Must be inaccessible to mosquitoes and animals! Should be accessible for cleaning!

30 Storage Tanks Polypropylene tanks are economical! Good for above ground storage! Must be reinforced for use below ground!

31 Storage Tanks Plastic above ground tank! Plastic below ground tank!

32 Storage Tanks Metal tanks are an economical choice! Corrugated, galvanized, zinc dipped! Generally available in 150 gallon to 2,500 gallon sizes! Due to aesthetics and freezing issues may not be the best choice for the northern climates!

33 Storage Tanks Metal above ground tank!

34 Storage Tanks Concrete Tanks! Poured in place or pre-fab! Prone to cracking and leaking! Ferro cement (Gunite and Shot Crete) are also used!

35 Storage Tanks Concrete tank!

36 Storage Tanks Matrix type tank!

37 Storage Tanks Fiberglass tanks are available in both horizontal and vertical cylinder shapes! Tanks under 1,000 gallons are expensive for their size! Available in sizes from 50 to 50,000 gallons!!

38 Storage Tanks Fiberglass!

39 Storage Tanks Rain barrels!

40 Storage Tank Siting Place as close as possible to both source and use points! If using above ground tanks they should be out of direct sun, if possible, and elevated to assist in pumping! Overflow run-off should not enter septic system drainfields! Consider the weight of the tank and stability of the ground!

41 Approximate Tank Capacities Height (feet) Round Cistern Capacity (Gallons)! 6 foot Diameter 12 foot Diameter 18 foot Diameter 6 1,269 5,076 11, ,692 6,768 15, ,115 8,460 19, ,538 10,152 22, ,961 11,844 26, ,384 13,535 30, ,807 15,227 34, ,230 16,919 38,069

42 Pumps A pump will be necessary to remove the water from the storage tank and pressurize it for the irrigation system.! Rule of Thumb: pumps are more reliable if they are submerged or flooded suction!!

43 Pumps Submersible pumps (well pumps)! May be mounted vertically or horizontally! Need flow sleeve to direct water over the motor for cooling! Must be accessible for service!

44 Pumps Standard submersible vs Bottom suction!

45 Pumps Submersible (sump type)! Pay attention to maximum head and flow! Read the pump curve!

46 Pumps End Suction! If possible mount as flooded suction! Suction lift mounting can cause loss of prime issues! Need dry, ventilated area!

47 Pumps Line Shaft Turbine! Bottom suction! High capacity! Reliable! Can be expensive!

48 Pump Controls Unless only a small drip irrigation system is used, potable water will probably be needed to supplement the stored rainwater.! Where is this potable water introduced?! Potable water added to the storage tank will decrease the capacity of the tank and require pump energy to pressurize it for the irrigation system! Potable water introduced into the irrigation mainline can take advantage of city pressure.! How should we control this potable water introduction?!

49 Pump Controls Basic pump controls should turn a pump on based on pressure and turn it off based on flow and pressure.! Pump station controls using a VFD and or PLC can control complex functions.! Pump start relay! OK for turning the pump on, but cannot recognize a low water condition!

50 BrainBox Monitors tank water level If enough water when irrigation starts, BrainBox allows the pump to supply the irrigation system If not enough tank water BrainBox opens an alternate supply feeding the tank or the irrigation system Float controls are wired for safe 24V reduced external voltage

51 Pump Controls Liquid level sensors! Low level to shut off pump! High level to allow the pump to restart! Pump Intake! Use a floating intake to take in the cleanest water!

52 Filtration Foot Valves L-Line T-Line Disc Y-Strainer Self Flushing Sand Media Sand Separator UV Filter

53 Estimating Collection Amount The roof catchment area is the footprint of the roof. Basically the length of the building times the width.! A house that has a footprint of 50 feet long by 30 feet wide has a footprint of 1,500 square feet.! In an average rain event, for each inch of rainfall each square foot of roof typically collects.6233 gallons of rain.! Of that 25 to 30 percent is typically lost before entering the holding tank/cistern.!

54 System Sizing How much water do you need?! Use historical ET to estimate the seasonal irrigation water requirement! Consider a residential property with a ¼ acre yard and a house with a footprint of 50 x 30!

55 Roof Calculations SUPPLY (Gallons) = (CATCHMENT AREA (FT2) x RAINFALL (inches)) x(.75 x.6233 GAL/CF) Supply (Gallons) = 1,500 sf x 1 x (.75 x.6233) Supply (Gallons) = gallons per inch of rainfall Note: 1000 Sq. Ft. of roof yields 620 Gallons of Water from 1 of Rain

56 Questions?