Drip Irrigation - Penn State University
Content
DRIP IRRIGATION SYSTEM
by Albert Jarrett, Professor of Biological Engineering Penn State University
3/19/2010
The Pennsylvania Protocol
In Chapter 73 (Conventional). (Conventional).
In-Ground Systems (Limiting Zone >60 in). In-
Beds. Trenches. Subsurface Sand Filters.
Elevated Sand Mounds (Limiting Zone >20 in). Individual Residential Spray Irrigation System
Bedrock Limiting Zone > 16 in. Water Table Limiting Zone >10 in.
3/19/2010
Drip Irrigation
Drip Irrigation is an Alternate On-Lot OnDisposal System. The following slides present the drip irrigation system concept in some detail. This presentation ends with an example that shows the design process.
Soil Conditions:
Rock Limiting Zone 26 inches. Seasonal High Water Table Limiting Zone 20 inches. Slope 25%. 25%. 26 inches 20 inches
Soil Conditions
No Perc Test is required. Soil profile must be evaluated by a licensed soil scientist who evaluates the probes. Soils must be well drained or moderately well drained.
Soil Conditions
Soil Scientist¶s Report Maximum soil linear load rate (Gal/ft/d) [based on maximum daily flow] Horizontal linear load (Gal/d) [based on average daily flow]. Depth of drip tubing. Minimum spacing between drip tubes.
Drip Irrigation Overview w/ Aerobic Tank
Major Components
Filtration Hydraulic Pump Tank
Hydraulic Unit Zones
Treatment Tank
Drip Irrigation Overview w/ Sand Filter
Major Components
Hydraulic Pump Tank
Hydraulic Unit Zones
Treatment Tank Filtration
Treatment Processes
From Home to Treatment Tank. Septic Tank Solids settle Scum floats to surface Two Chamber Septic Tanks required.
Treatment Tank
TwoTwo-Chamber Septic Tank
Treatment Processes
From the Treatment Tank to the Filtration Unit. Secondary Treatment is required if Limiting Zone < 48 inches. Aerobic Treatment Tank Free Access Sand Filter (5 gal/d/ft2) Subsurface Sand Filter (0.8 gal/d/ft2)
Aerobic Treatment Tank
Free Access Sand Filter (side view)
Free Access Sand Filter (top view)
Subsurface Sand Filter (partial side view)
Subsurface Sand Filter (top view)
Treatment Processes
From the Filtration Unit to the Hydraulic Unit to the Drip Zones. The filtered effluent flows, by gravity, into the Hydraulic Unit Pump Tank: Here a series of float switches controls the flow of partially treated wastewater to the Hydraulic Unit. The Hydraulic Unit is 2 (or 3) disc filters that provide final filtration before application to the soil.
Hydraulic Unit Pump Tank
Pump Tank
Receives Filter Unit effluent Doses effluent to Hydraulic Unit and Zones. Contains pump-control switches. pump-
Hydraulic Unit
Contains 2 (or 3) disc filters.
Provides final filtration before going to drip zones. Must have at least 2 zones.
Drip Zones
Drip Zones
Each long section of a zone is on the contour. Each zone may have more than one lateral. Each lateral may have more than one zone. Each zone must have a supply and return line. Air vents are also required on each zone.
Drip System
With Water Limiting Zone u 20 inches.
0 to 12 in deep; 6 to 12 in of cover over the tubing. Maybe as small as 8 in
Emitters spaced 2 feet apart; 0.68 gal/d/em
u 20 inches
Drip System
With Rock Limiting Zone u 26 inches.
0 to 12 in deep; 6 to 12 in of cover over the tubing.
Emitters spaced 2 feet apart; 0.68 gal/d/em
u 20 inches
Drip System; 3rd Configuration
With Rock Limiting Zone u 20 inches.
Driplines laid on soil surface and covered with native topsoil.
Emitters spaced 2 feet apart; 0.65 gal/d/em
u 20 inches
Simple Example
A site, with a 3-bdrm home, has a well drained soil 3with a rock limiting zone at 35 inches and a seasonal high watertable at 25 inches. The site has a 10% slope. Soil Scientist report states: Maximum soil linear load rate = 0.25 gal/ft/d. Horizontal linear load = 3.5 gal/ft/d. Drip tubing spacing to be at least 2.0 feet. Tubing to be buried at least 6 inches deep.
Example
Site Geometry Width of lot along the contour = 130 ft. Distance from dose tank to Hydraulic Unit = 20 ft. Hydraulic Unit is 7 feet above the enabler float in dose tank. Distance from Hydraulic Unit to zones = 100 feet. Distance from zones to bldg sewer = 140 feet. Elevation increase from Hydraulic Unit to drip zones = 20 feet.
Soil Conditions:
Rock Limiting Zone = 35 inches. Seasonal High Water Table Limiting Zone = 25 inches. Slope = 10%. 10%. = 35 inches
= 25 inches
Soil Conditions:
Rock Limiting Zone = 35 inches.
6 inches
29 inches
= 35 inches
Soil Conditions:
Seasonal High Water Table Limiting Zone = 25 inches.
6 inches
= 25 inches
19 inches
Example
Soil Scientist¶s Report Maximum linear loading rate = 0.25 gal/d/ft. Horizontal linear load = 3.5 gal/d/ft
Example
The septic tank is sized as per Chapter 73 for a 3 bdrm home. This is a drip system, so a Secondary Treatment unit is needed. The choices are: Aerobic Treatment Tank Free Access sand filter. Subsurface sand filter. See the Secondary Treatment slides for sizing guidelines for these units.
Example
Following the Pre-treatment unit the effluent Prewill flow into a Dose/Pump tank.
Example
The Pump/Dose Tank must be at least 2 times larger than the maximum daily flow. The maximum daily flow from a 3-bdrm 3home is taken to be 400 gpd. Therefore the Pump/Dose Tank must be at least 800 gallons in size.
Example
In a Drip Irrigation system the effluent is pumped from the Dose/Pump Tank to the Hydraulic Unit and on to the drip zones.
Example
The Hydraulic Unit controls the flow to zones and backflushing. Two units are available: 2-disc and 3-disc units. 23 The two-disc unit supports: two 1,200 ft of drip tubing/zone. Tubing forward flush rate = 15 gpm. 4 zones and one return connection. 4,800 ft of drip tubing (4x1200).
Example
Forward Field Flush Flow Rate: Dose flow rate to the drip emitters PLUS Field Flush flow rate needed to maintain a velocity in the drip tubing of 2 fps. This is set to 1.6 gpm/lateral within each zone.
Example
Length of drip tubing required: Max daily flow/linear loading rate 400 gpd/0.25 gal/d-ft = 1600 ft. gal/d We will use 2 zones. 1600 ft/2 = 800 ft/zone
Supply Line
Example
Return line
Each zone will consist of 8 runs of 100 ft each. 4 laterals, each 200 ft long. (2 runs/lateral). Run
Air Vent & Check Valve
Lateral (4)
Example
Check to make sure the runs are long enough«. Based on the Average daily flow 400 gpd (.5) = 200 gpd. Horizontal linear load = 3.5 gal/g-ft gal/g Minimum run length = 200/3.5 = 57 ft. Our runs are 100 ft long; Okay.
Example (Summary)
Peak daily flow = 400 gpd. Soil linear load = 0.25 gal/d-ft. gal/dTotal tubing length required = 1600 ft. 2 zones used. Hydraulic Unit used = 2 disc. Tubing length/zone = 1600/2 = 800 ft. No. Laterals/zone = 4 Lateral length = 800/4 = 200 ft. Run length = 100 ft. Horizontal linear load = 3.5 gal/d-ft. gal/dMinimum run length = 200/3.5 = 57 ft.
Example
Flow required to each zone during Forward Field Flush Hydraulic Condition. Need: Dose flow rate PLUS Field flush flow rate
Example
Dose flow rate (for each zone)=
lengthofzone 0.65 gph x distbetweenemitters 60 min/ hr
800 ft 0.65 gph x ! 4.3 gpm 2 ft / emitters 60 min/ hr
Example
Field flush flow rate/zone = 1.6 gpm/lateral (to maintain a velocity of 2 fps in drip tubes) =1.6gpm/lat x 4 laterals = 6.4 gpm/zone Total flow required during Forward Field Flush is 4.3 + 6.4 = 10.7 gpm.
Example (Pump Selection)
The remaining task is to size the pump. This means that we must determine: System¶s total head System¶s maximum flow rate.
Example (Bernoulli Analysis)
The Total Head for the pump in the Dose Tank is the sum of three components: Head Loss in all the pipes. Pressure needed to run the system, either the emitters or the Hydraulic Unit. Elevation difference between the water level in the dose tank to the drip zones. The Total Head is the SUM of these three values.
Example (Friction; HL)
The Head Loss (or Friction) is the most difficult to determine. This must be done in parts: HL in the pipe from the dose tank to the Hydraulic Unit. HL in the Zone supply pipes. HL in the drip lines. HL in the Zone return pipes.
Example (HL from tank to HU)
First size this pipe to carry the maximum flow. During dosing the pipe will carry 10.7 gpm. During back flushing this pipe will carry 15 gpm. Size for the 15 gpm. gpm.
Example (Size the pipe to HU)
With a design flow rate of 15 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.5-inch pipe to keep the 1.5velocity above 2.0 fps. (V = 2.35 fps). This 1.5-in PVC pipe has a friction 1.5factor, Fc = 0.63 psi/100 ft or 1.46 ft/100 ft.
Example (HL from tank to HU)
Before we can determine the HL in this pipe, we must determine the length of the pipe including the equivalent length for the various elbows, valves etc. The length of pipe was given at 20 ft. The equivalent length is specified as 50 ft. The total length is 20 + 50 = 70 ft.
Example (HL from tank to HU)
The HL is calculated from: HL = FcL HL = 1.46 ft/100 ft(70ft) = 1.02 ft.
Example (HL in Supply Pipe)
First size the Supply pipe to carry the maximum flow. During dosing the pipe will carry 10.7 gpm. Not used during back flushing. Size for the 10.7 gpm. gpm.
Example (Size the Supply Pipe)
With a design flow rate of 10.7 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.25-inch pipe to keep the 1.25velocity above 2.0 fps. (V = 2.20 fps). This 1.25-in PVC pipe has a friction 1.25factor, Fc = 0.70 psi/100 ft or 1.62 ft/100 ft.
Example (HL in Supply Pipe)
Before we can determine the HL in this pipe, we must determine the length of the supply pipe [this is assumed to be a straight pipe]. The length of pipe was given at 100 ft.
Example (HL in Supply Pipe)
The HL is calculated from: HL = FcL HL = 1.62 ft/100 ft(100ft) = 1.62 ft.
Example (HL in Drip Zone)
We desire to deliver 10.7 gpm to each zone. Of this water: 4.3 gpm will go out the emitters. 6.4 gpm will flush through the drip lines and be returned to the building sewer.
Example (HL in Drip Zone)
The drip supplier specifies that for 200-ft 200laterals, the losses in the drip lines will be 18 ft (Table 3A).
Example (HL in Return Pipe)
First size the Supply pipe to carry the maximum flow. During dosing the return pipe will carry 6.4 gpm. Not used during back flushing. Size for the 6.4 gpm. gpm.
Example (Size the Return Pipe)
With a design flow rate of 6.4 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.0-inch pipe to keep the 1.0velocity above 2.0 fps. (V = 2.30 fps). This 1.00-in PVC pipe has a friction 1.00factor, Fc = 0.95 psi/100 ft or 2.19 ft/100 ft.
Example (HL in Return Pipe)
Before we can determine the HL in this pipe, we must determine the length of the supply pipe [this is assumed to be a straight pipe]. The length of pipe was given at 140 ft.
Example (HL in Return Pipe)
The HL is calculated from: HL = FcL HL = 2.19 ft/100 ft(140ft) = 3.07 ft.
Example (HL Summary)
The Head Loss (or Friction) for these four sections of our system is: HL Dose Tank to the HU = 1.02 ft. HL Supply Pipe = 1.62 ft. HL Drip Lines = 18 ft. HL Return Pipe = 3.07 ft Total HL = 23.7 ft.
Example (Pressure Requirements)
The Pressure needed to operate the various components of the system: Pressure to Back Flush the Hydraulic Unit. Pressure to Operate the Emitters. At this time these requirements are not provided by the manufacturer.
Example (Pressure Requirements)
Without having worked with this system, I would assume the following: The pressure needed to run the HU should be 10 to 20 psi (23 to 46 ft). The pressure needed to make the emitters function properly is generally about 10 psi (23 ft). The total pressure requirement = 46 + 23 = 69 ft.
Example (Elevation Difference)
Elevation differences include: Rise from enabler float in dose tank to Hydraulic Unit (+ 7 ft). Rise from the Hydraulic Unit to the drip Zones (+20 ft). Total elevation rise = 7 + 20 = 27 ft.
Bernoulli Summary (Dosing)
The total energy needed to run this system is: HL = 23.7 ft. Pressure = 69 ft. Elevation rise = 27 ft. Total during dosing = 120 ft. Flow rate = 10.7 gpm.
Bernoulli Summary (Back Flushing)
The total energy needed to run this system is: HL = 115 + 1.02 = 116 ft. Pressure = 0 ft. Elevation rise = 7 ft. Total during dosing = 123 ft. Flow rate = 15 gpm.
Example (Pump Requirement)
For Dosing HT = 120 ft Q = 10.7 gpm For Back Flushing HT = 123 ft. Q = 15 gpm. Pump Design HT = 123 ft. Q = 15 gpm. gpm.
Example (Time/Dose)
Average daily flow = 200 gpd Each zone accounts for 50% of flow. Zone 1 = 100 gpd Zone 2 = 100 gpd At 4 doses /zone/day; each dose must apply 25 gal. Time/dose = 25 gal/dose/4.3 gpm = 5.8 min
Example (Time/Dose)
Summary: We dose 5.8 min 4 times each day to supply 25 gal/dose or 100 gal/day to each zone. With 2 zones we apply 200 gal/day; the avrage daily flow from the 3 bdrm home.
Example (Time/Dose)
Under condition of Maximum daily flow (400 gpd) We apply 200 gal/zone/day At 4.3 gpm (25 gal/dose). 200/25 = 8 doses/day.
Thank You
by Albert Jarrett, Professor of Biological Engineering Penn State University
3/19/2010
The Pennsylvania Protocol
In Chapter 73 (Conventional). (Conventional).
In-Ground Systems (Limiting Zone >60 in). In-
Beds. Trenches. Subsurface Sand Filters.
Elevated Sand Mounds (Limiting Zone >20 in). Individual Residential Spray Irrigation System
Bedrock Limiting Zone > 16 in. Water Table Limiting Zone >10 in.
3/19/2010
Drip Irrigation
Drip Irrigation is an Alternate On-Lot OnDisposal System. The following slides present the drip irrigation system concept in some detail. This presentation ends with an example that shows the design process.
Soil Conditions:
Rock Limiting Zone 26 inches. Seasonal High Water Table Limiting Zone 20 inches. Slope 25%. 25%. 26 inches 20 inches
Soil Conditions
No Perc Test is required. Soil profile must be evaluated by a licensed soil scientist who evaluates the probes. Soils must be well drained or moderately well drained.
Soil Conditions
Soil Scientist¶s Report Maximum soil linear load rate (Gal/ft/d) [based on maximum daily flow] Horizontal linear load (Gal/d) [based on average daily flow]. Depth of drip tubing. Minimum spacing between drip tubes.
Drip Irrigation Overview w/ Aerobic Tank
Major Components
Filtration Hydraulic Pump Tank
Hydraulic Unit Zones
Treatment Tank
Drip Irrigation Overview w/ Sand Filter
Major Components
Hydraulic Pump Tank
Hydraulic Unit Zones
Treatment Tank Filtration
Treatment Processes
From Home to Treatment Tank. Septic Tank Solids settle Scum floats to surface Two Chamber Septic Tanks required.
Treatment Tank
TwoTwo-Chamber Septic Tank
Treatment Processes
From the Treatment Tank to the Filtration Unit. Secondary Treatment is required if Limiting Zone < 48 inches. Aerobic Treatment Tank Free Access Sand Filter (5 gal/d/ft2) Subsurface Sand Filter (0.8 gal/d/ft2)
Aerobic Treatment Tank
Free Access Sand Filter (side view)
Free Access Sand Filter (top view)
Subsurface Sand Filter (partial side view)
Subsurface Sand Filter (top view)
Treatment Processes
From the Filtration Unit to the Hydraulic Unit to the Drip Zones. The filtered effluent flows, by gravity, into the Hydraulic Unit Pump Tank: Here a series of float switches controls the flow of partially treated wastewater to the Hydraulic Unit. The Hydraulic Unit is 2 (or 3) disc filters that provide final filtration before application to the soil.
Hydraulic Unit Pump Tank
Pump Tank
Receives Filter Unit effluent Doses effluent to Hydraulic Unit and Zones. Contains pump-control switches. pump-
Hydraulic Unit
Contains 2 (or 3) disc filters.
Provides final filtration before going to drip zones. Must have at least 2 zones.
Drip Zones
Drip Zones
Each long section of a zone is on the contour. Each zone may have more than one lateral. Each lateral may have more than one zone. Each zone must have a supply and return line. Air vents are also required on each zone.
Drip System
With Water Limiting Zone u 20 inches.
0 to 12 in deep; 6 to 12 in of cover over the tubing. Maybe as small as 8 in
Emitters spaced 2 feet apart; 0.68 gal/d/em
u 20 inches
Drip System
With Rock Limiting Zone u 26 inches.
0 to 12 in deep; 6 to 12 in of cover over the tubing.
Emitters spaced 2 feet apart; 0.68 gal/d/em
u 20 inches
Drip System; 3rd Configuration
With Rock Limiting Zone u 20 inches.
Driplines laid on soil surface and covered with native topsoil.
Emitters spaced 2 feet apart; 0.65 gal/d/em
u 20 inches
Simple Example
A site, with a 3-bdrm home, has a well drained soil 3with a rock limiting zone at 35 inches and a seasonal high watertable at 25 inches. The site has a 10% slope. Soil Scientist report states: Maximum soil linear load rate = 0.25 gal/ft/d. Horizontal linear load = 3.5 gal/ft/d. Drip tubing spacing to be at least 2.0 feet. Tubing to be buried at least 6 inches deep.
Example
Site Geometry Width of lot along the contour = 130 ft. Distance from dose tank to Hydraulic Unit = 20 ft. Hydraulic Unit is 7 feet above the enabler float in dose tank. Distance from Hydraulic Unit to zones = 100 feet. Distance from zones to bldg sewer = 140 feet. Elevation increase from Hydraulic Unit to drip zones = 20 feet.
Soil Conditions:
Rock Limiting Zone = 35 inches. Seasonal High Water Table Limiting Zone = 25 inches. Slope = 10%. 10%. = 35 inches
= 25 inches
Soil Conditions:
Rock Limiting Zone = 35 inches.
6 inches
29 inches
= 35 inches
Soil Conditions:
Seasonal High Water Table Limiting Zone = 25 inches.
6 inches
= 25 inches
19 inches
Example
Soil Scientist¶s Report Maximum linear loading rate = 0.25 gal/d/ft. Horizontal linear load = 3.5 gal/d/ft
Example
The septic tank is sized as per Chapter 73 for a 3 bdrm home. This is a drip system, so a Secondary Treatment unit is needed. The choices are: Aerobic Treatment Tank Free Access sand filter. Subsurface sand filter. See the Secondary Treatment slides for sizing guidelines for these units.
Example
Following the Pre-treatment unit the effluent Prewill flow into a Dose/Pump tank.
Example
The Pump/Dose Tank must be at least 2 times larger than the maximum daily flow. The maximum daily flow from a 3-bdrm 3home is taken to be 400 gpd. Therefore the Pump/Dose Tank must be at least 800 gallons in size.
Example
In a Drip Irrigation system the effluent is pumped from the Dose/Pump Tank to the Hydraulic Unit and on to the drip zones.
Example
The Hydraulic Unit controls the flow to zones and backflushing. Two units are available: 2-disc and 3-disc units. 23 The two-disc unit supports: two 1,200 ft of drip tubing/zone. Tubing forward flush rate = 15 gpm. 4 zones and one return connection. 4,800 ft of drip tubing (4x1200).
Example
Forward Field Flush Flow Rate: Dose flow rate to the drip emitters PLUS Field Flush flow rate needed to maintain a velocity in the drip tubing of 2 fps. This is set to 1.6 gpm/lateral within each zone.
Example
Length of drip tubing required: Max daily flow/linear loading rate 400 gpd/0.25 gal/d-ft = 1600 ft. gal/d We will use 2 zones. 1600 ft/2 = 800 ft/zone
Supply Line
Example
Return line
Each zone will consist of 8 runs of 100 ft each. 4 laterals, each 200 ft long. (2 runs/lateral). Run
Air Vent & Check Valve
Lateral (4)
Example
Check to make sure the runs are long enough«. Based on the Average daily flow 400 gpd (.5) = 200 gpd. Horizontal linear load = 3.5 gal/g-ft gal/g Minimum run length = 200/3.5 = 57 ft. Our runs are 100 ft long; Okay.
Example (Summary)
Peak daily flow = 400 gpd. Soil linear load = 0.25 gal/d-ft. gal/dTotal tubing length required = 1600 ft. 2 zones used. Hydraulic Unit used = 2 disc. Tubing length/zone = 1600/2 = 800 ft. No. Laterals/zone = 4 Lateral length = 800/4 = 200 ft. Run length = 100 ft. Horizontal linear load = 3.5 gal/d-ft. gal/dMinimum run length = 200/3.5 = 57 ft.
Example
Flow required to each zone during Forward Field Flush Hydraulic Condition. Need: Dose flow rate PLUS Field flush flow rate
Example
Dose flow rate (for each zone)=
lengthofzone 0.65 gph x distbetweenemitters 60 min/ hr
800 ft 0.65 gph x ! 4.3 gpm 2 ft / emitters 60 min/ hr
Example
Field flush flow rate/zone = 1.6 gpm/lateral (to maintain a velocity of 2 fps in drip tubes) =1.6gpm/lat x 4 laterals = 6.4 gpm/zone Total flow required during Forward Field Flush is 4.3 + 6.4 = 10.7 gpm.
Example (Pump Selection)
The remaining task is to size the pump. This means that we must determine: System¶s total head System¶s maximum flow rate.
Example (Bernoulli Analysis)
The Total Head for the pump in the Dose Tank is the sum of three components: Head Loss in all the pipes. Pressure needed to run the system, either the emitters or the Hydraulic Unit. Elevation difference between the water level in the dose tank to the drip zones. The Total Head is the SUM of these three values.
Example (Friction; HL)
The Head Loss (or Friction) is the most difficult to determine. This must be done in parts: HL in the pipe from the dose tank to the Hydraulic Unit. HL in the Zone supply pipes. HL in the drip lines. HL in the Zone return pipes.
Example (HL from tank to HU)
First size this pipe to carry the maximum flow. During dosing the pipe will carry 10.7 gpm. During back flushing this pipe will carry 15 gpm. Size for the 15 gpm. gpm.
Example (Size the pipe to HU)
With a design flow rate of 15 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.5-inch pipe to keep the 1.5velocity above 2.0 fps. (V = 2.35 fps). This 1.5-in PVC pipe has a friction 1.5factor, Fc = 0.63 psi/100 ft or 1.46 ft/100 ft.
Example (HL from tank to HU)
Before we can determine the HL in this pipe, we must determine the length of the pipe including the equivalent length for the various elbows, valves etc. The length of pipe was given at 20 ft. The equivalent length is specified as 50 ft. The total length is 20 + 50 = 70 ft.
Example (HL from tank to HU)
The HL is calculated from: HL = FcL HL = 1.46 ft/100 ft(70ft) = 1.02 ft.
Example (HL in Supply Pipe)
First size the Supply pipe to carry the maximum flow. During dosing the pipe will carry 10.7 gpm. Not used during back flushing. Size for the 10.7 gpm. gpm.
Example (Size the Supply Pipe)
With a design flow rate of 10.7 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.25-inch pipe to keep the 1.25velocity above 2.0 fps. (V = 2.20 fps). This 1.25-in PVC pipe has a friction 1.25factor, Fc = 0.70 psi/100 ft or 1.62 ft/100 ft.
Example (HL in Supply Pipe)
Before we can determine the HL in this pipe, we must determine the length of the supply pipe [this is assumed to be a straight pipe]. The length of pipe was given at 100 ft.
Example (HL in Supply Pipe)
The HL is calculated from: HL = FcL HL = 1.62 ft/100 ft(100ft) = 1.62 ft.
Example (HL in Drip Zone)
We desire to deliver 10.7 gpm to each zone. Of this water: 4.3 gpm will go out the emitters. 6.4 gpm will flush through the drip lines and be returned to the building sewer.
Example (HL in Drip Zone)
The drip supplier specifies that for 200-ft 200laterals, the losses in the drip lines will be 18 ft (Table 3A).
Example (HL in Return Pipe)
First size the Supply pipe to carry the maximum flow. During dosing the return pipe will carry 6.4 gpm. Not used during back flushing. Size for the 6.4 gpm. gpm.
Example (Size the Return Pipe)
With a design flow rate of 6.4 gpm and using PVC-schedule-40 pipe, we will PVC-scheduleneed a 1.0-inch pipe to keep the 1.0velocity above 2.0 fps. (V = 2.30 fps). This 1.00-in PVC pipe has a friction 1.00factor, Fc = 0.95 psi/100 ft or 2.19 ft/100 ft.
Example (HL in Return Pipe)
Before we can determine the HL in this pipe, we must determine the length of the supply pipe [this is assumed to be a straight pipe]. The length of pipe was given at 140 ft.
Example (HL in Return Pipe)
The HL is calculated from: HL = FcL HL = 2.19 ft/100 ft(140ft) = 3.07 ft.
Example (HL Summary)
The Head Loss (or Friction) for these four sections of our system is: HL Dose Tank to the HU = 1.02 ft. HL Supply Pipe = 1.62 ft. HL Drip Lines = 18 ft. HL Return Pipe = 3.07 ft Total HL = 23.7 ft.
Example (Pressure Requirements)
The Pressure needed to operate the various components of the system: Pressure to Back Flush the Hydraulic Unit. Pressure to Operate the Emitters. At this time these requirements are not provided by the manufacturer.
Example (Pressure Requirements)
Without having worked with this system, I would assume the following: The pressure needed to run the HU should be 10 to 20 psi (23 to 46 ft). The pressure needed to make the emitters function properly is generally about 10 psi (23 ft). The total pressure requirement = 46 + 23 = 69 ft.
Example (Elevation Difference)
Elevation differences include: Rise from enabler float in dose tank to Hydraulic Unit (+ 7 ft). Rise from the Hydraulic Unit to the drip Zones (+20 ft). Total elevation rise = 7 + 20 = 27 ft.
Bernoulli Summary (Dosing)
The total energy needed to run this system is: HL = 23.7 ft. Pressure = 69 ft. Elevation rise = 27 ft. Total during dosing = 120 ft. Flow rate = 10.7 gpm.
Bernoulli Summary (Back Flushing)
The total energy needed to run this system is: HL = 115 + 1.02 = 116 ft. Pressure = 0 ft. Elevation rise = 7 ft. Total during dosing = 123 ft. Flow rate = 15 gpm.
Example (Pump Requirement)
For Dosing HT = 120 ft Q = 10.7 gpm For Back Flushing HT = 123 ft. Q = 15 gpm. Pump Design HT = 123 ft. Q = 15 gpm. gpm.
Example (Time/Dose)
Average daily flow = 200 gpd Each zone accounts for 50% of flow. Zone 1 = 100 gpd Zone 2 = 100 gpd At 4 doses /zone/day; each dose must apply 25 gal. Time/dose = 25 gal/dose/4.3 gpm = 5.8 min
Example (Time/Dose)
Summary: We dose 5.8 min 4 times each day to supply 25 gal/dose or 100 gal/day to each zone. With 2 zones we apply 200 gal/day; the avrage daily flow from the 3 bdrm home.
Example (Time/Dose)
Under condition of Maximum daily flow (400 gpd) We apply 200 gal/zone/day At 4.3 gpm (25 gal/dose). 200/25 = 8 doses/day.
Thank You
