drip irrigation - penn state university

8/9/2019 Drip Irrigation - Penn State University

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3/19/2010

DRIP IRRIGATIONSYSTEM

bybyAlbert Jarrett,Albert Jarrett,

Professor of BiologicalProfessor of Biological

EngineeringEngineeringPenn State UniversityPenn State University


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3/19/2010

The Pennsylvania Protocol

In Chapter 73 (In Chapter 73 (ConventionalConventional).). InIn--Ground Systems (Limiting Zone >60 in).Ground Systems (Limiting Zone >60 in).

Beds.Beds.

Trenches.Trenches.

Subsurface Sand Filters.Subsurface Sand Filters. Elevated Sand Mounds (Limiting Zone >20 in).Elevated Sand Mounds (Limiting Zone >20 in).

Individual Residential Spray Irrigation SystemIndividual Residential Spray Irrigation System

Bedrock Limiting Zone > 16 in.Bedrock Limiting Zone > 16 in.

Water Table Limiting Zone >10 in.Water Table Limiting Zone >10 in.


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Drip Irrigation Drip Irrigation is an Alternate OnDrip Irrigation is an Alternate On--LotLot

Disposal System.Disposal System.

The following slides present the dripThe following slides present the dripirrigation system concept in some detail.irrigation system concept in some detail.

This presentation ends with an exampleThis presentation ends with an example

that shows the design process.that shows the design process.


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Soil Conditions:

Rock Limiting ZoneRock Limiting Zone 26 inches.26 inches.

Seasonal High Water Table LimitingSeasonal High Water Table Limiting

ZoneZone 20 inches.20 inches.

SlopeSlope 25% 25%..

26 inches 20 inches


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Soil Conditions No Perc Test is required.No Perc Test is required.

Soil profile must beSoil profile must be

evaluated by a licensedevaluated by a licensedsoil scientist whosoil scientist who

evaluates the probes.evaluates the probes.

Soils must be wellSoils must be well

drained or moderatelydrained or moderatelywell drained.well drained.


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Drip Irrigation

Overview w/ Aerobic Tank Major ComponentsMajor Components

Treatment Tank FiltrationHydraulic

Pump Tank

Hydraulic

Unit

Zones


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Drip Irrigation

Overview w/ Sand Filter Major ComponentsMajor Components

Treatment TankFiltration

Hydraulic

Pump Tank

Hydraulic

Unit

Zones


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Treatment Processes

From Home to Treatment Tank.From Home to Treatment Tank.

Septic TankSeptic Tank

Solids settleSolids settle

Scum floats to surfaceScum floats to surface

Two Chamber Septic TanksTwo Chamber Septic Tanks

required.required.


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Treatment Tank

TwoTwo--Chamber Septic TankChamber Septic Tank


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Treatment Processes

From the Treatment Tank to the FiltrationFrom the Treatment Tank to the Filtration

Unit.Unit.

Secondary Treatment is required ifSecondary Treatment is required if

Limiting Zone < 48 inches.Limiting Zone < 48 inches.

Aerobic Treatment TankAerobic Treatment Tank

Free Access Sand Filter (5 gal/d/ftFree Access Sand Filter (5 gal/d/ft22))

Subsurface Sand Filter (0.8 gal/d/ftSubsurface Sand Filter (0.8 gal/d/ft22))


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Aerobic Treatment Tank


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Free Access Sand Filter

(side view)


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Free Access Sand Filter

(top view)


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Subsurface Sand Filter

(partial side view)


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Treatment Processes From the Filtration Unit to the Hydraulic UnitFrom the Filtration Unit to the Hydraulic Unit

to the Drip Zones.to the Drip Zones.

The filtered effluent flows, by gravity, intoThe filtered effluent flows, by gravity, intothe Hydraulic Unit Pump Tank:the Hydraulic Unit Pump Tank:

Here a series of float switches controlsHere a series of float switches controlsthe flow of partially treated wastewaterthe flow of partially treated wastewaterto the Hydraulic Unit.to the Hydraulic Unit.

The Hydraulic Unit is 2 (or 3) discThe Hydraulic Unit is 2 (or 3) discfilters that provide final filtrationfilters that provide final filtrationbefore application to the soil.before application to the soil.


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Hydraulic Unit Pump Tank

Pump TankPump Tank

Receives Filter Unit effluentReceives Filter Unit effluent

Doses effluent to Hydraulic Unit and Zones.Doses effluent to Hydraulic Unit and Zones.

Contains pumpContains pump--control switches.control switches.


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Hydraulic Unit Contains 2 (or 3)Contains 2 (or 3)

disc filters.disc filters.

Provides finalProvides finalfiltration beforefiltration before

going to dripgoing to drip

zones.zones.

Must have at leastMust have at least

2 zones.2 zones.


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Drip Zones


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Drip Zones Each long sectionEach long section

of a zone is on theof a zone is on thecontour.contour.

Each zone mayEach zone mayhave more thanhave more than

one lateral.one lateral. Each lateral mayEach lateral may

have more thanhave more thanone zone.one zone.

Each zone mustEach zone musthave a supply andhave a supply and

return line.return line. Air vents are alsoAir vents are also

required on eachrequired on eachzone.zone.


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Drip System With Water LimitingWith Water Limiting

ZoneZone uu 20 inches.20 inches.

u 20 inchesEmitters spaced 2 feet

apart; 0.68 gal/d/em

0 to 12 in deep; 6 to 12 in

of cover over the tubing.

Maybe as small as 8 in


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Drip System With Rock LimitingWith Rock Limiting

ZoneZone uu 26 inches.26 inches.



0 to 12 in deep; 6 to 12 in

of cover over the tubing.


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Drip System; 3rd

Configuration

With Rock Limiting ZoneWith Rock Limiting Zone uu 20 inches.20 inches.



Driplines laid on soil

surface and covered

with native topsoil.


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Simple Example A site, with a 3A site, with a 3--bdrm home, has a well drained soilbdrm home, has a well drained soil

with a rock limiting zone at 35 inches and a seasonalwith a rock limiting zone at 35 inches and a seasonalhigh watertable at 25 inches.high watertable at 25 inches.

The site has a 10% slope.The site has a 10% slope.

Soil Scientist report states:Soil Scientist report states:

Maximum soil linear load rate = 0.25 gal/ft/d.Maximum soil linear load rate = 0.25 gal/ft/d.

Horizontal linear load = 3.5 gal/ft/d.Horizontal linear load = 3.5 gal/ft/d.

Drip tubing spacing to be at least 2.0 feet.Drip tubing spacing to be at least 2.0 feet. Tubing to be buried at least 6 inches deep.Tubing to be buried at least 6 inches deep.


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Soil Conditions:

Rock Limiting ZoneRock Limiting Zone == 35 inches.35 inches.


ZoneZone == 25 inches.25 inches.

SlopeSlope = 10%= 10%..

= 35 inches

= 25 inches


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Soil Conditions:

Rock Limiting ZoneRock Limiting Zone == 35 inches.35 inches.

= 35 inches

6 inches

29 inches


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Soil Conditions:


ZoneZone == 25 inches.25 inches.

= 25 inches

6 inches

19 inches


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Example Soil Scientists ReportSoil Scientists Report

Maximum linear loading rate = 0.25Maximum linear loading rate = 0.25

gal/d/ft.gal/d/ft.

Horizontal linear load = 3.5 gal/d/ftHorizontal linear load = 3.5 gal/d/ft


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Example The septic tank is sized as per Chapter 73 forThe septic tank is sized as per Chapter 73 for

a 3 bdrm home.a 3 bdrm home.

This is a drip system, so a SecondaryThis is a drip system, so a SecondaryTreatment unit is needed. The choices are:Treatment unit is needed. The choices are:

Aerobic Treatment TankAerobic Treatment Tank

Free Access sand filter.Free Access sand filter.

Subsurface sand filter.Subsurface sand filter. See the Secondary Treatment slides forSee the Secondary Treatment slides for

sizing guidelines for these units.sizing guidelines for these units.


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Example Following the PreFollowing the Pre--treatment unit the effluenttreatment unit the effluent

will flow into a Dose/Pump tank.will flow into a Dose/Pump tank.


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Example The Pump/Dose Tank must be at leastThe Pump/Dose Tank must be at least

2 times larger than the maximum daily2 times larger than the maximum daily

flow.flow.

The maximum daily flow from a 3The maximum daily flow from a 3--bdrmbdrm

home is taken to be 400 gpd.home is taken to be 400 gpd.

Therefore the Pump/Dose Tank must beTherefore the Pump/Dose Tank must beat least 800 gallons in size.at least 800 gallons in size.


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Example In a Drip Irrigation system the effluent isIn a Drip Irrigation system the effluent is

pumped from the Dose/Pump Tank to thepumped from the Dose/Pump Tank to the

Hydraulic Unit and on to the drip zones.Hydraulic Unit and on to the drip zones.


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Example The Hydraulic Unit controls the flow toThe Hydraulic Unit controls the flow to

zones and backflushing. Two units arezones and backflushing. Two units are

available: 2available: 2--disc and 3disc and 3--disc units.disc units.The twoThe two--disc unit supports:disc unit supports:

1,200 ft of drip tubing/zone.1,200 ft of drip tubing/zone.

Tubing forward flush rate = 15 gpm.Tubing forward flush rate = 15 gpm.

4 zones and one return connection.4 zones and one return connection.

4,800 ft of drip tubing (4x1200).4,800 ft of drip tubing (4x1200).


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Example Length of drip tubing required:Length of drip tubing required:

Max daily flow/linear loading rateMax daily flow/linear loading rate

400 gpd/0.25 gal/d400 gpd/0.25 gal/d--ft = 1600 ft.ft = 1600 ft.

We will use 2 zones.We will use 2 zones.

1600 ft/2 = 800 ft/zone1600 ft/2 = 800 ft/zone


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Example Each zone will consist ofEach zone will consist of

8 runs of 100 ft each.8 runs of 100 ft each.

4 laterals, each 200 ft long. (24 laterals, each 200 ft long. (2

runs/lateral).runs/lateral).

Supply Line

Return line

Air Vent & Check Valve

Run

Lateral (4)


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Example Check to make sure the runs are longCheck to make sure the runs are long

enough.enough.

Based on the Average daily flowBased on the Average daily flow

400 gpd (.5) = 200 gpd.400 gpd (.5) = 200 gpd.

Horizontal linear load = 3.5 gal/gHorizontal linear load = 3.5 gal/g--ftft

Minimum run length = 200/3.5 = 57 ft.Minimum run length = 200/3.5 = 57 ft.

Our runs are 100 ft long; Okay.Our runs are 100 ft long; Okay.


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Example (Summary) Peak daily flow = 400 gpd.Peak daily flow = 400 gpd. Soil linear load = 0.25 gal/dSoil linear load = 0.25 gal/d--ft.ft.

Total tubing length required = 1600 ft.Total tubing length required = 1600 ft.

2 zones used.2 zones used.

Hydraulic Unit used = 2 disc.Hydraulic Unit used = 2 disc. Tubing length/zone = 1600/2 = 800 ft.Tubing length/zone = 1600/2 = 800 ft.

No. Laterals/zone = 4No. Laterals/zone = 4

Lateral length = 800/4 = 200 ft.Lateral length = 800/4 = 200 ft.

Run length = 100 ft.Run length = 100 ft. Horizontal linear load = 3.5 gal/dHorizontal linear load = 3.5 gal/d--ft.ft.

Minimum run length = 200/3.5 = 57 ft.Minimum run length = 200/3.5 = 57 ft.


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Example Flow required to each zone duringFlow required to each zone during

Forward Field Flush HydraulicForward Field Flush Hydraulic

Condition.Condition.

Need:Need:

Dose flow rate PLUSDose flow rate PLUS

Field flush flow rateField flush flow rate


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Example Dose flow rate (for each zone)=Dose flow rate (for each zone)=

hrgphx

nemittersdistbetweenelengthofzo

min/6065.0

gpmhr

gphxemittersft

ft 3.4min/6065.0

/2800 !


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Example Field flush flow rate/zone = 1.6Field flush flow rate/zone = 1.6

gpm/lateral (to maintain a velocity of 2gpm/lateral (to maintain a velocity of 2

fps in drip tubes)fps in drip tubes)=1.6gpm/lat x 4 laterals = 6.4=1.6gpm/lat x 4 laterals = 6.4

gpm/zonegpm/zone

Total flow required during Forward FieldTotal flow required during Forward FieldFlush is 4.3 + 6.4 = 10.7 gpm.Flush is 4.3 + 6.4 = 10.7 gpm.


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Example (Pump Selection) The remaining task is to size the pump.The remaining task is to size the pump.

This means that we must determine:This means that we must determine:

Systems total headSystems total head

Systems maximum flow rate.Systems maximum flow rate.


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Example (Bernoulli Analysis) The Total Head for the pump in the DoseThe Total Head for the pump in the Dose

Tank is the sum of three components:Tank is the sum of three components:

Head Loss in all the pipes.Head Loss in all the pipes. Pressure needed to run the system, eitherPressure needed to run the system, either

the emitters or the Hydraulic Unit.the emitters or the Hydraulic Unit.

Elevation difference between the waterElevation difference between the waterlevel in the dose tank to the drip zones.level in the dose tank to the drip zones.

The Total Head is the SUM of these threeThe Total Head is the SUM of these threevalues.values.


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Example (Friction; HL) The Head Loss (or Friction) is the mostThe Head Loss (or Friction) is the most

difficult to determine. This must be donedifficult to determine. This must be done

in parts:in parts:HHLL in the pipe from the dose tank toin the pipe from the dose tank to

the Hydraulic Unit.the Hydraulic Unit.

HHLL in the Zone supply pipes.in the Zone supply pipes.

HHLL in the drip lines.in the drip lines.

HHLL in the Zone return pipes.in the Zone return pipes.


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Example (HL from tank to HU) First size this pipe to carry theFirst size this pipe to carry the

maximum flow.maximum flow.

During dosing the pipe will carry 10.7During dosing the pipe will carry 10.7

gpm.gpm.

During back flushing this pipe will carryDuring back flushing this pipe will carry

15 gpm.15 gpm. Size for theSize for the 15 gpm15 gpm..


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Example (Size the pipe to HU) With a design flow rate of 15 gpm andWith a design flow rate of 15 gpm and

using PVCusing PVC--scheduleschedule--40 pipe, we will40 pipe, we will

need a 1.5need a 1.5--inch pipe to keep theinch pipe to keep thevelocity above 2.0 fps. (V = 2.35 fps).velocity above 2.0 fps. (V = 2.35 fps).

This 1.5This 1.5--in PVC pipe has a frictionin PVC pipe has a friction

factor, Ffactor, Fcc = 0.63 psi/100 ft or 1.46 ft/100= 0.63 psi/100 ft or 1.46 ft/100ft.ft.


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Example (HL from tank to HU) The HThe HLL is calculated from:is calculated from:

HHLL = F= FccLL

HHLL = 1.46 ft/100 ft(70ft) = 1.02 ft.= 1.46 ft/100 ft(70ft) = 1.02 ft.


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Example (HL in Supply Pipe) First size the Supply pipe to carry theFirst size the Supply pipe to carry the

maximum flow.maximum flow.

During dosing the pipe will carry 10.7During dosing the pipe will carry 10.7gpm.gpm.

Not used during back flushing.Not used during back flushing.

Size for theSize for the 10.7 gpm10.7 gpm..


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Example (HL in Supply Pipe) Before we can determine the HBefore we can determine the HLL in thisin this

pipe, we must determine the length ofpipe, we must determine the length of

the supply pipe [this is assumed to be athe supply pipe [this is assumed to be astraight pipe].straight pipe].

The length of pipe was given at 100The length of pipe was given at 100

ft.ft.


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Example (HL in Supply Pipe) The HThe HLL is calculated from:is calculated from:

HHLL = F= FccLL



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Example (HL inD

rip Zone) We desire to deliver 10.7 gpm to eachWe desire to deliver 10.7 gpm to each

zone. Of this water:zone. Of this water:

4.3 gpm will go out the emitters.4.3 gpm will go out the emitters.

6.4 gpm will flush through the drip6.4 gpm will flush through the drip

lines and be returned to the buildinglines and be returned to the building

sewer.sewer.


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Example (HL inD

rip Zone) The drip supplier specifies that for 200The drip supplier specifies that for 200--ftft

laterals, the losses in the drip lines willlaterals, the losses in the drip lines will

be 18 ft (Table 3A).be 18 ft (Table 3A).


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Example (Size the Return Pipe) With a design flow rate of 6.4 gpm andWith a design flow rate of 6.4 gpm and

using PVCusing PVC--scheduleschedule--40 pipe, we will40 pipe, we will

need a 1.0need a 1.0--inch pipe to keep theinch pipe to keep thevelocity above 2.0 fps. (V = 2.30 fps).velocity above 2.0 fps. (V = 2.30 fps).

This 1.00This 1.00--in PVC pipe has a frictionin PVC pipe has a friction

factor, Ffactor, Fcc = 0.95 psi/100 ft or 2.19 ft/100= 0.95 psi/100 ft or 2.19 ft/100ft.ft.


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Example (HL in Return Pipe) Before we can determine the HBefore we can determine the HLL in thisin this

pipe, we must determine the length ofpipe, we must determine the length of

the supply pipe [this is assumed to be athe supply pipe [this is assumed to be astraight pipe].straight pipe].

The length of pipe was given at 140The length of pipe was given at 140

ft.ft.


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Example (HL in Return Pipe) The HThe HLL is calculated from:is calculated from:

HHLL = F= FccLL



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Example (HL Summary) The Head Loss (or Friction) for theseThe Head Loss (or Friction) for these

four sections of our system is:four sections of our system is:

HHLL Dose Tank to the HU = 1.02 ft.Dose Tank to the HU = 1.02 ft.

HHLL Supply Pipe = 1.62 ft.Supply Pipe = 1.62 ft.

HHLL Drip Lines = 18 ft.Drip Lines = 18 ft.

HHLL Return Pipe = 3.07 ftReturn Pipe = 3.07 ft

Total HTotal HLL = 23.7 ft.= 23.7 ft.


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Example (Pressure Requirements) Without having worked with this system, IWithout having worked with this system, I

would assume the following:would assume the following:

The pressure needed to run the HU shouldThe pressure needed to run the HU shouldbe 10 to 20 psi (23 to 46 ft).be 10 to 20 psi (23 to 46 ft).

The pressure needed to make the emittersThe pressure needed to make the emittersfunction properly is generally about 10 psifunction properly is generally about 10 psi(23 ft).(23 ft).

The total pressure requirement = 46 + 23 =The total pressure requirement = 46 + 23 =69 ft.69 ft.


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Example (ElevationD

ifference) Elevation differences include:Elevation differences include:

Rise from enabler float in dose tank toRise from enabler float in dose tank to

Hydraulic Unit (+ 7 ft).Hydraulic Unit (+ 7 ft).

Rise from the Hydraulic Unit to theRise from the Hydraulic Unit to the

drip Zones (+20 ft).drip Zones (+20 ft).

Total elevation rise = 7 + 20 = 27 ft.Total elevation rise = 7 + 20 = 27 ft.


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Bernoulli Summary (D

osing) The total energy needed to run thisThe total energy needed to run this

system is:system is:

HHLL = 23.7 ft.= 23.7 ft.

Pressure = 69 ft.Pressure = 69 ft.

Elevation rise = 27 ft.Elevation rise = 27 ft.

Total during dosing = 120 ft.Total during dosing = 120 ft.

Flow rate = 10.7 gpm.Flow rate = 10.7 gpm.


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Bernoulli Summary (Back Flushing)

The total energy needed to run thisThe total energy needed to run this

system is:system is:

HHLL = 115 + 1.02 = 116 ft.= 115 + 1.02 = 116 ft.

Pressure = 0 ft.Pressure = 0 ft.

Elevation rise = 7 ft.Elevation rise = 7 ft.

Total during dosing = 123 ft.Total during dosing = 123 ft.

Flow rate = 15 gpm.Flow rate = 15 gpm.


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Example (Pump Requirement) ForDosingForDosing

HHTT = 120 ft= 120 ft

Q = 10.7 gpmQ = 10.7 gpm

For Back FlushingFor Back Flushing

HHTT = 123 ft.= 123 ft.

Q = 15 gpm.Q = 15 gpm.

Pump DesignPump Design

HHTT = 123 ft.= 123 ft. Q = 15 gpmQ = 15 gpm..


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Example (Time/D

ose)Average daily flow = 200 gpdAverage daily flow = 200 gpd

Each zone accounts for 50% of flow.Each zone accounts for 50% of flow.

Zone 1 = 100 gpdZone 1 = 100 gpdZone 2 = 100 gpdZone 2 = 100 gpd

At 4 doses /zone/day; each dose mustAt 4 doses /zone/day; each dose must

apply 25 gal.apply 25 gal. Time/dose = 25 gal/dose/4.3 gpmTime/dose = 25 gal/dose/4.3 gpm

= 5.8 min= 5.8 min


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Example (Time/D

ose) Under condition of Maximum daily flowUnder condition of Maximum daily flow

(400 gpd)(400 gpd)

We apply 200 gal/zone/dayWe apply 200 gal/zone/day

At 4.3 gpm (25 gal/dose).At 4.3 gpm (25 gal/dose).

200/25 = 8 doses/day.200/25 = 8 doses/day.


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Thank You

drip irrigation - penn state university

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