06_dilg_salintubig - design guidelines for water supply system

7/28/2019 06_DILG_Salintubig - Design Guidelines for Water Supply System

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SPRING BOX DESIGN: The appropriate type of intake box suitable for the

spring is selected from the Standard Type of Springs, depending upon the actual condition in the

field.

Spring box should be provided with adequateoverflow pipe so as not to damage the spring box intimes where the spring discharge increases due toexcessive rains or where the aquifer level isfluctuating.


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SPRING BOXDESIGN 1:


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SPRING BOXDESIGN 2:


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TYPICAL WELL DESIGN:


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SELECTION OF CASING DIAMETER:

Maximum discharge rate for certain diameters


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PUMP DESIGN:

Pump size should be determined byWell Yield

Number of Operating Hours

Fill and Draw or Float System

Hydraulic Zones

Delivery Pressures


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Determination of Pump Discharge:

If the pump is used directly to supply water to the distribution system, the capacitymust be equal to PHD

If the water distribution system has areservoir, the pump capacity must be equalto MDD


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Pump Selection:

Centrifugal Pumps , If TDH = < 6 meters

Jet Pumps, If TDH = 6 to 20 meters

Submersible Pumps, If TDH = > 20 meters

TDH is the sum of the depth of pumping water

level + maximum reservoir elevation + frictionlosses


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Calculate Pump Capacity:

Power (Kw) = 9.8 x (1/eff) x Q x TDH

Power (HP) = Kw/0.746

Where:

Q = Discharge (cms)TDH = Total Dynamic Head (m)eff = Pump Efficiency

Pump Efficiency:

Centrifugal Pump:

30 60%

Jetmatic Pump:20 30%

Submersible Pump:50 60%


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DESIGN OF RESERVOIR:

Reservoirs are employed in the distribution system tomeet the peak demand (if water source is available), toequalize pressure and to store water.

The elevation of the bottom tank is computed to be atleast equal to but preferably higher than the elevation of the farthest and highest tap in the system plus theminimum pressure head plus the total head losses fromthe point up to source.


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Reservoir Design Procedure :

Location of the Reservoir It should be located, if possible at the elevated places and or central to thedistr ibution system, for economic reason.

Calculate Reservoir CapacityThe capacity should not be more than the necessary to supplement the

ADD to the system during times of peak demand.Rule of thumb = Reservoir capacity should be at least 25% of ADD

Determine type of Reservoir It maybe Elevated or Ground Level Reservoi r type. The volume of storage,

location, material and choice of type of reservoir depend primarily on costand what is available.


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PIPELINE DESIGN:

In applying the design minimum requirements for the design of pipeline,

the following should be considered:

It must be designed to handle the PHD of the service area

The minimum Pressure at the remotest end of the system (tap stand

or communal faucet) shall not be less than 2.0 meters

The pipeline must be designed considering that the Maximum

Velocity in the pipe is 3m/s for main pipes and distribution pipes.

Ensure that there is no negative hydraulic gradient or negative

pressure in the pipelines.


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Pipeline Design Procedure:

Calculate the flows in the laterals and main pipes using the

PHD

Calculate pipe diameters corresponding to the pipe flow using

the Hazen-Williams Equation Formula

Check Maximum Velocity in pipe should not be 3 m/s

Check Headloss due to friction

Choose appropriate route to the storage reservoir or to thedistribution system and add the losses of all sections along

the route to get the total head loss.


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Pipeline Design Procedure:

Compute losses such that the pressures at the reservoir and at the

distr ibution system meet the design cri teria. If pressure are to high

reduce the size of the pipe.

If losses are too large, the reservoir may be too high or the pump

required may be large, redesign the pipelines using larger diameters

until the losses are reasonable.

Determine the location of the valves, fitt ings, etc. Normally air release

valves are located at the peak and sag port ion along the pipeline.

Blow-offs should be located at end points or lowest point. If possible

blow-offs should be near the drainage outfall.


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Hazens William Formula:

hL= 10.667 x Q^1.852

x L

C^ 1.852 x D^ 4.87

Where:

Q = flow in cmsL = Length in m

C = Friction CoefficientD = Diameter in meters

Recommended Pipe C Values(New Pipes)

Pipe Material DiameterRecommended

C-Values

Plastic> 300 mm 150

< 300 mm 140

Iron> 300 mm 140

< 300 mm 130


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EXAMPLE 1

Barangay A100 HH

Barangay B120 HH

Barangay C80 HH

Barangay E350 HH

Barangay F400 HH

Barangay D200 HH

Proposed Source 2 - aDeep WellConfirmed yield, 10 lps

Proposed Source 1Spring, 12 km awayConfirmed yield, 20 lps

Proposed Source 2 - bDeep WellConfirmed yield, 8 lps

reservoir


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EXAMPLE 1

No ROW problem anticipated All identified water sources have confirmed yields, and of acceptable water qualityWater rights can be secured by LGUWater source site are free from environmental and socialconstraints

Proposed Service Area, 5 Barangays(# OF PAX/HH =5.5)

A 550 pax 100 HHB 660 120C 440 80D 1,100 200E 1,925 350F 2,200 400

Proposed Water Sources:

1. Spring5 kms awaysufficient elevationconfirmed yield, 20 lps

2. Groundwater Well no. 1 10 lps, 50 m away

Well no. 2 8 lps, 250 m


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EXAMPLE 1

Population Projections

Water Demand:at 110 liters/cap/dayadd 30% non-revenue water

BarangayName Population Households Population Households Population Households Population Households

A 550 100 584 106 629 114 638 116B 660 120 701 127 755 137 766 139C 440 80 467 85 503 91 510 93D 1,100 200 1,168 212 1,258 229 1,276 232E 1,925 350 2,044 372 2,202 400 2,233 406F 2,200 400 2,336 425 2,516 457 2,552 464

TOTAL 6,875 1,250 7,300 1,327 7,863 1,430 7,975 1,450

Year 1 Year 5 Year 10 Year 15

Water Demand Projection (lps)BarangayName

A 0.91 0.97 1.04 1.06

B 1.09 1.16 1.25 1.27C 0.73 0.77 0.83 0.84D 1.82 1.93 2.08 2.11E 3.19 3.38 3.64 3.70F 3.64 3.87 4.16 4.22

TOTAL 11.38 12.08 13.01 13.20

151 5 10

Growth Rate:Year 5 = 1.21%Year 10 = 1.35%Year 15 = 0.99%


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EXAMPLE 1

Key Questions (1/2)

How many barangays would be servedSocial/politicalWater source availabilityCost constraint

Would the source be sufficient to supply thedemand

First year, immediate and long-terms (design

horizon)Most advantageous source option (groundwater,spring or combination)


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EXAMPLE 1

Key Questions (2/2)

Development PlanStaged implementation or full implementationCost requirement (consider source option)

Investment CostOperation and Maintenance Cost

Probable water tariff

Financial & Economic IndicatorsWillingness-to-connect and willingness-to-pay


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EXAMPLE 1

Other Considerations

Reservoir RequirementsMaybe needed to provide supplemental flowduring peak periods

Or simply to balance pressures during peakflowsNormally sized at 20% to 30% of the averageday demandShould consider fill-and-draw systems or float systems


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END OF PRESENTATION

06_dilg_salintubig - design guidelines for water supply system

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