Title: DRIP IRRIGATION SYSTEM
1DRIP IRRIGATION SYSTEM
- by
- Albert Jarrett,
- Professor of Biological Engineering
- Penn State University
2The Pennsylvania Protocol
- In Chapter 73 (Conventional).
- In-Ground Systems (Limiting Zone gt60 in).
- Beds.
- Trenches.
- Subsurface Sand Filters.
- Elevated Sand Mounds (Limiting Zone gt20 in).
- Individual Residential Spray Irrigation System
- Bedrock Limiting Zone gt 16 in.
- Water Table Limiting Zone gt10 in.
3Drip Irrigation
- Drip Irrigation is an Alternate On-Lot Disposal
System. - The following slides present the drip irrigation
system concept in some detail. - This presentation ends with an example that shows
the design process.
4Soil Conditions
- Rock Limiting Zone 26 inches.
- Seasonal High Water Table Limiting Zone 20
inches. - Slope 25.
26 inches
20 inches
5Soil 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.
6Soil Conditions
- Soil Scientists 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.
7Drip Irrigation Overview w/ Aerobic Tank
Hydraulic Unit
Hydraulic Pump Tank
Filtration
Treatment Tank
Zones
8Drip Irrigation Overview w/ Sand Filter
Hydraulic Unit
Hydraulic Pump Tank
Treatment Tank
Zones
Filtration
9Treatment Processes
- From Home to Treatment Tank.
- Septic Tank
- Solids settle
- Scum floats to surface
- Two Chamber Septic Tanks required.
10Treatment Tank
11Treatment Processes
- From the Treatment Tank to the Filtration Unit.
- Secondary Treatment is required if Limiting Zone
lt 48 inches. - Aerobic Treatment Tank
- Free Access Sand Filter (5 gal/d/ft2)
- Subsurface Sand Filter (0.8 gal/d/ft2)
12Aerobic Treatment Tank
13Free Access Sand Filter (side view)
14Free Access Sand Filter (top view)
15Subsurface Sand Filter (partial side view)
16Subsurface Sand Filter(top view)
17Treatment 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.
18Hydraulic Unit Pump Tank
- Pump Tank
- Receives Filter Unit effluent
- Doses effluent to Hydraulic Unit and Zones.
- Contains pump-control switches.
19Hydraulic Unit
- Contains 2 (or 3) disc filters.
- Provides final filtration before going to drip
zones. - Must have at least 2 zones.
20Drip Zones
21Drip 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.
22Drip System
- With Water Limiting Zone ? 20 inches.
? 20 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
Maybe as small as 8 in
23Drip System
- With Rock Limiting Zone ? 26 inches.
? 20 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
24Drip System 3rd Configuration
- With Rock Limiting Zone ? 20 inches.
Driplines laid on soil surface and covered with
native topsoil.
Emitters spaced 2 feet apart 0.65 gal/d/em
? 20 inches
25Simple Example
- A site, with a 3-bdrm home, has a well drained
soil with 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.
-
26Example
- 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.
27Soil Conditions
- Rock Limiting Zone 35 inches.
- Seasonal High Water Table Limiting Zone 25
inches. - Slope 10.
35 inches
25 inches
28Soil Conditions
- Rock Limiting Zone 35 inches.
6 inches
29 inches
35 inches
29Soil Conditions
- Seasonal High Water Table Limiting Zone 25
inches.
6 inches
25 inches
19 inches
30Example
- Soil Scientists Report
- Maximum linear loading rate 0.25 gal/d/ft.
- Horizontal linear load 3.5 gal/d/ft
31Example
- 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.
32Example
- Following the Pre-treatment unit the effluent
will flow into a Dose/Pump tank.
33Example
- The Pump/Dose Tank must be at least 2 times
larger than the maximum daily flow. - The maximum daily flow from a 3-bdrm home is
taken to be 400 gpd. - Therefore the Pump/Dose Tank must be at least 800
gallons in size.
34Example
- In a Drip Irrigation system the effluent is
pumped from the Dose/Pump Tank to the Hydraulic
Unit and on to the drip zones.
35Example
- The Hydraulic Unit controls the flow to zones and
backflushing. Two units are available 2-disc and
3-disc units. - The two-disc unit supports
- 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).
36Example
- 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.
37Example
- Length of drip tubing required
- Max daily flow/linear loading rate
- 400 gpd/0.25 gal/d-ft 1600 ft.
- We will use 2 zones.
- 1600 ft/2 800 ft/zone
38Example
Supply Line
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)
39Example
- 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
- Minimum run length 200/3.5 57 ft.
- Our runs are 100 ft long Okay.
40Example (Summary)
- Peak daily flow 400 gpd.
- Soil linear load 0.25 gal/d-ft.
- Total 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.
- Minimum run length 200/3.5 57 ft.
41Example
- Flow required to each zone during Forward Field
Flush Hydraulic Condition. - Need
- Dose flow rate PLUS
- Field flush flow rate
42Example
- Dose flow rate (for each zone)
43Example
- 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.
44Example (Pump Selection)
- The remaining task is to size the pump.
- This means that we must determine
- Systems total head
- Systems maximum flow rate.
45Example (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.
46Example (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.
47Example (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.
48Example (Size the pipe to HU)
- With a design flow rate of 15 gpm and using
PVC-schedule-40 pipe, we will need a 1.5-inch
pipe to keep the velocity above 2.0 fps. (V
2.35 fps). - This 1.5-in PVC pipe has a friction factor, Fc
0.63 psi/100 ft or 1.46 ft/100 ft.
49Example (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.
50Example (HL from tank to HU)
- The HL is calculated from
- HL FcL
- HL 1.46 ft/100 ft(70ft) 1.02 ft.
51Example (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.
52Example (Size the Supply Pipe)
- With a design flow rate of 10.7 gpm and using
PVC-schedule-40 pipe, we will need a 1.25-inch
pipe to keep the velocity above 2.0 fps. (V
2.20 fps). - This 1.25-in PVC pipe has a friction factor, Fc
0.70 psi/100 ft or 1.62 ft/100 ft.
53Example (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.
54Example (HL in Supply Pipe)
- The HL is calculated from
- HL FcL
- HL 1.62 ft/100 ft(100ft) 1.62 ft.
55Example (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.
56Example (HL in Drip Zone)
- The drip supplier specifies that for 200-ft
laterals, the losses in the drip lines will be 18
ft (Table 3A).
57Example (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.
58Example (Size the Return Pipe)
- With a design flow rate of 6.4 gpm and using
PVC-schedule-40 pipe, we will need a 1.0-inch
pipe to keep the velocity above 2.0 fps. (V
2.30 fps). - This 1.00-in PVC pipe has a friction factor, Fc
0.95 psi/100 ft or 2.19 ft/100 ft.
59Example (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.
60Example (HL in Return Pipe)
- The HL is calculated from
- HL FcL
- HL 2.19 ft/100 ft(140ft) 3.07 ft.
61Example (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.
62Example (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.
63Example (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.
64Example (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.
65Bernoulli 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.
66Bernoulli 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.
67Example (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.
68Example (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
69Example (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.
70Example (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.
71Thank You