Water Supply and Open Wells Overview

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Questions and Answers

What should be considered when planning future water supply requirements?

Understanding past consumption patterns only

Future requirements if known (correct)

The current population only

The distance to the nearest water source

Which of the following is a factor in determining the water supply arrangement?

The color of the water

Public opinion about water sources

Whether the supply will be metered (correct)

The age of the existing infrastructure

What type of investigation is necessary for collecting water supply data?

Social impact analysis

Site investigation and yield test (correct)

Historical drought assessments

Census of the surrounding population

Which standard specifies the drinking water quality requirements in India?

IS:10500 - 1991 Signup and view all the answers

What role do engineering department officials have regarding water supply arrangements?

They must be informed about rainfall and supply conditions Signup and view all the answers

What manual is mentioned for the treatment and management of water supply?

Manual on water supply and treatment Signup and view all the answers

What is a key checklist item for preparing water supply proposals?

Details of pumping arrangement Signup and view all the answers

What is an objective of keeping up-to-date with supply conditions from various sources?

To prevent breakdown in supply of adequate water Signup and view all the answers

How many workshops are required per person according to the specified standards?

45 Signup and view all the answers

What is the washing requirement for carriages on broad gauge (BG)?

3600 per carriage Signup and view all the answers

For estimating water requirements at a railway station, how is the number of passengers calculated?

Entraining plus half of detraining Signup and view all the answers

What is the washing requirement for platform cleaning?

10 per sqm Signup and view all the answers

How much water is typically required for a hospital bed?

450 per bed Signup and view all the answers

What is the safe yield of open wells determined by?

Critical velocity and seasonal conditions Signup and view all the answers

What is the approximate number of gardens per hectare stated in the guidelines?

22500 Signup and view all the answers

What should be the capacity of a water source during summer months?

Supply in eight hours Signup and view all the answers

What is the minimum residual pressure required at the ferrule points for a single storey building?

7 m Signup and view all the answers

What is the minimum velocity of underground water in average conditions for effective yield?

750 mm per hour Signup and view all the answers

How often should fire service systems be checked for adequacy?

Occasionally Signup and view all the answers

What is the recommended horizontal separation distance between a water main and an existing sewer line?

3 m Signup and view all the answers

For multi-storeyed buildings needing higher pressure, what is a suggested method of maintaining adequate supply?

Providing boosters to the system Signup and view all the answers

Which of the following statements about the distribution system’s design considerations is true?

It may not exceed a residual pressure of 22 m. Signup and view all the answers

What arrangement is recommended for the main to avoid dead ends?

Grid formation or network Signup and view all the answers

What is the typical pressure range for PSC pipes in water supply mains?

6 Kg/cm2 to 20 Kg/cm2 Signup and view all the answers

Which of the following is NOT an advantage of PVC pipes?

Greatly affected by UV light Signup and view all the answers

What should be the minimum depth for the top of the pipe in areas with severe frost?

1 metre Signup and view all the answers

What is a recommended installation practice for gravity line pipes?

Follow the contour of the ground avoiding abrupt changes in gradient Signup and view all the answers

What should be provided at all summits and sags in a water supply pipeline?

Air valves at summits and scour valves at sags Signup and view all the answers

What is the resistance property of PVC pipes when compared to metals?

Low thermal retentivity Signup and view all the answers

At what working pressures can PVC pipes operate effectively?

From 2 to 10 kg/cm2 Signup and view all the answers

What is a key requirement for laying spigot and socket pipes?

Sockets should face the water flow direction Signup and view all the answers

What happens to PVC pipes when exposed to ultraviolet light?

They undergo accelerated decomposition Signup and view all the answers

What should be ensured for the trench bed when installing pipes?

It should be finished to an even gradient and level Signup and view all the answers

What percentage of the outlay of the water supply scheme do distribution accounts typically cover?

40 to 70% Signup and view all the answers

Who is responsible for submitting reports on the cleaning of tanks?

Section Engineer (Works) Signup and view all the answers

What should be included in the periodical reports regarding the state of tanks?

Condition of painting and corrosion Signup and view all the answers

Which distribution system is recommended for general convenience?

Grid system Signup and view all the answers

What distribution system is deemed adequate only for small water supply systems?

Tree system Signup and view all the answers

The economical diameter of a pipeline is chiefly based on which factors?

Head-losses and velocities Signup and view all the answers

When designing a distribution system, what consumption estimation period is suggested?

10 to 16 hours Signup and view all the answers

What should be guaranteed when junctions or branches are laid in separate mains?

No connection of drinking and other water supplies Signup and view all the answers

The design of a separate distribution system for water unfit for drinking aims to address which aspect?

Avoidable contamination of potable supplies Signup and view all the answers

What system is advised for ensuring water supply from two directions?

Grid system Signup and view all the answers

What is the maximum permissible limit for total dissolved solids in drinking water?

2000 mg/l Signup and view all the answers

Which of the following has no permissible relaxation limit?

Arsenic concentration Signup and view all the answers

What is the undesirable limit for taste and odour in drinking water?

Objectionable Signup and view all the answers

What is the permissible limit for nitrates in drinking water when referring to the maximum concentration?

45 mg/l Signup and view all the answers

Which of the following substances has the lowest permissible limit in drinking water?

Cadmium Signup and view all the answers

What is the main purpose of conducting a recuperation test in a well?

To determine the yield by analyzing drawdown and inflow Signup and view all the answers

Which factor is NOT considered when determining the size and depth of an open well?

Soil temperature of the surrounding area Signup and view all the answers

In sandy soil, what strategy can be utilized if the yield with a drop of 2 meters is insufficient?

Increase the well’s diameter or supplement with a tube well Signup and view all the answers

What effect does increasing the 'drop' in an open well have on the critical velocity?

It increases the critical velocity and may cause blowing of the soil Signup and view all the answers

When improving yield in moorum and porous rock, what is a viable method?

Drive adits into the sides of the well Signup and view all the answers

What should be done to determine if deeper strata in a well are porous?

Perform a bore to ascertain porosity Signup and view all the answers

What is a consequence of not managing surface runoff in the vicinity of a well?

Potential decrease in inflow from porous rock Signup and view all the answers

How does constructing a bund on the upstream side of the well affect yield?

It increases the yield by holding back surface flow Signup and view all the answers

What is the maximum suction lift that may be expected at sea level?

7 meters Signup and view all the answers

Which component should be present near the pump to prevent backflow?

Non-return valve Signup and view all the answers

For what purpose should a foot-valve be included in the suction pipe?

To prevent air from entering Signup and view all the answers

What design aspect should be considered when constructing foundations for pumps?

Load-bearing strength Signup and view all the answers

What is the recommended velocity of water in the delivery pipe?

2.5 m/s Signup and view all the answers

When a driving unit is available, what is the preferred choice for powering pumps?

Electric motor Signup and view all the answers

What is necessary to ensure the suction pipe system functions effectively?

Air-tight construction Signup and view all the answers

What type of joint is required between the pump and the delivery system?

Dismantling joint Signup and view all the answers

What additional valve should be included alongside the delivery valve?

Sluice valve Signup and view all the answers

What may be used when centrifugal pumps cannot be installed close to the water-table?

Airlift pumps Signup and view all the answers

What is the primary focus of a sanitary survey in water supply assessment?

To estimate potential pollution from water sources Signup and view all the answers

When considering the adequacy of a water supply scheme, what factor should NOT be overlooked?

Accessibility to the proposed water source site Signup and view all the answers

Which of the following assessments is essential for determining if treatment of water is required?

Conducting tests for water quality and impurities Signup and view all the answers

Which factor should be incorporated into the total demand assessment for a water supply scheme?

All domestic and ancillary usage needs Signup and view all the answers

What is a significant implication of not considering future water requirements in a scheme?

Insufficient supply during peak demand periods Signup and view all the answers

Which aspect of water source assessment focuses on the need for treatment?

Quality test results for water samples Signup and view all the answers

What key consideration is crucial when determining the water supply for fire needs?

Including fire demand in the total water requirement assessment Signup and view all the answers

Which of the following does NOT contribute to the assessment of fire demand in a water supply scheme?

Estimating the number of fire events in a year Signup and view all the answers

Which factor is vital to evaluate during the treatment line considerations for water supply?

Quality standards of the target water supply Signup and view all the answers

In the context of water supply planning, what should be done to address potential contamination risks?

Conduct regular sanitary surveys of areas near water sources Signup and view all the answers

What is the recommended action for coagulants added to raw water?

They should be added in the correct proportion based on turbidity. Signup and view all the answers

How frequently should the Assistant Engineer conduct inspections of the water purification plant?

Once a year. Signup and view all the answers

What precaution should be taken regarding the storage of disinfectants?

Proper storage and safety precautions must be followed. Signup and view all the answers

What must the Divisional Engineer do during their annual inspection?

Inspect the water works and record notes in the Inspection Register. Signup and view all the answers

What is the purpose of maintaining an Inspection Register at each water purification work?

To enable Inspecting Officers to record notes during inspections. Signup and view all the answers

What is required for cleaning and washing filters according to the specified guidelines?

They must be cleaned and washed as prescribed at regular intervals. Signup and view all the answers

Which staff member is responsible for ensuring prompt action on inspection notes?

Assistant Engineer. Signup and view all the answers

What must each installation maintain alongside the detailed instructions on operation?

Duty lists of the staff posted there. Signup and view all the answers

What is a key aspect of the inspection by the Divisional Engineer?

To inspect in detail and record observations. Signup and view all the answers

What should happen if repairs or replacements are required after inspections?

They should be addressed promptly. Signup and view all the answers

Study Notes

Water Supply

Water supply plans should consider the expected demands, the source type, and potential issues like water quality.
The number of people using the system, their water use habits, and the environment will impact the daily water needs.
The design of the system should accommodate the maximum estimated daily consumption during the busiest hours.
To avoid water shortages, the source needs to be able to provide enough water to meet daily requirements, even during summer months.
The quantity of water required for trains originating from a station is equal to the full capacity of the tanks for all coaches.
For trains scheduled for watering at other stations, only 75% filling capacity may be considered.
Open wells are a common source of water for railway purposes, but their yield depends on the speed of water flow through the soil.

Open Wells

Open wells should be tested before being used for water supply and should be investigated in the dry season to understand soil conditions and water quality.
The safe yield of open wells is limited by the speed at which water can flow through the soil.
The yield of open wells is also known as their "effective yield."

PVC Pipes and their Advantages

The use of polyvinyl chloride (PVC) pipes is recommended for water mains due to their resistance to corrosion, low weight, strength, and easy installation.
They are also resistant to a wide range of chemicals and have good elastic properties.
PVC pipes are less expensive than metal pipes and do not pit or corrode in service.
PVC pipes are not recommended for uses above ground due to their sensitivity to ultraviolet light and temperature fluctuations.

Pipe Laying and Fitting Valves and Meters

To prevent water from flowing back, spigot and socket pipes should be assembled with the sockets facing the direction the water will flow.
The top of pipes should be buried below the surface of the ground, with extra depth in areas with freezing weather.
Air valves should be installed at all summits in a pipe system to release air in the pipes, while scour valves should be installed at all sags to remove sediment that collects in the lines.

Tank Cleaning

Reports on the cleaning of tanks should be submitted to the Assistant Engineer by the Section Engineer.
Tank cleaning reports should include information about the condition of external and internal paint, corrosion, and the date of each cleaning and painting action.

Layout of Distribution Systems

Distribution systems should be designed with the most suitable layout for the specific site, considering factors like head losses and water flow velocities.
The design of these systems should accommodate the maximum estimated daily consumption during the busiest hours, typically in 10 to 16 hours of operation.

Distribution Systems: Residual Pressure and Preventative Maintenance

The residual pressure at the water supply points is an important consideration. The system needs to be designed to ensure adequate pressure even during peak hours.
Preventative maintenance is critical to maintain the quality and efficiency of the distribution system.
It includes cleaning of pipe lines, as well as inspections to identify and address any potential issues.

Different Supply Sources

When separate mains for drinking water and other purposes like irrigation are present, it is vital to prevent the two supplies from mixing.
This involves a careful design of junctions and branches.
The economics of having a separate distribution system for water unfit for drinking purposes should be considered and weighed against the treatment cost of that water and supplying it through a single distribution system.

Protection Against Pollution

To prevent water contamination, water mains should be laid at least 3 m away from existing or proposed drains or sewer lines horizontally.
If proximity to sewer lines is unavoidable, the water main should be laid in a separate trench or on an undisturbed earth shelf located on one side of the sewer, with the water main's bottom placed at least 0.5 meters above the top of the sewer.

Preventing Dead Ends in Distribution Systems

The distribution system should be laid out in a grid formation or network to avoid dead ends.
This ensures water flow throughout the system, reducing the likelihood of stagnation and ensuring efficient supply to all connected points.

Geological Department Consultation

The Geological Department should be consulted in regards to the strata and source at the proposed site for wells.

Determining Well Yield

The yield of a test-well should be assessed by carrying out a recuperation test.
The recuperation test involves pumping the water out of the well until the level is below the normal water table, then measuring the rate at which the water level rises.
The results of the test should be plotted on a graph with draw down as the x-axis and the inflow in liters per hour as the y-axis.

Determining Well Size

The diameter and depth of an open well should be determined based on the maximum daily water requirement, taking into account future demands.
The size of an open well should be considered in light of the normal water table, critical velocity of flow, and suction lift.
The normal water table is the water level in a well that has not been pumped for 24 hours.
The critical velocity of inflow is the maximum speed at which water can enter a well without causing the well to collapse or become unstable.
The suction lift for open wells is limited due to the maximum suction lift of reciprocating pumps (around 7 meters).
For tube wells where centrifugal pumps cannot be installed near the water table, airlift pumps can be used.
Airlift pumps are less efficient than centrifugal pumps and should not be used for capacities exceeding a certain limit.

Improving Well Yields in Sandy Soil

If the yield of a well in sandy soil is insufficient with a 2-meter drop, a larger diameter well should be considered.
Alternatively, a tube-well can be sunk inside the open well to supplement the yield.
Increasing the drop will increase the critical velocity, leading to blowing of the sandy soil and possible subsidence and staining.

Improving Well Yields in Moorum and Porous Rock

If yield is insufficient, deepening the well may improve yield if the lower strata is porous.
This can be determined through boring.
Driving adits into the sides of the well and increasing the number of weep holes can increase the yield.

Open Well Construction

The well's foundation must be strong enough to absorb vibrations and provide a rigid support for the base plate.
The foundation should be designed according to IS:2974 Part IV - 1979.
The suction lift should be minimized, with a maximum suction lift of 7 meters at sea level.
The suction pipe should be airtight with minimal bends and equipped with a foot valve.
A non-return valve (reflux valve) and a delivery valve (sluice or butterfly valve) are required.
The non-return valve should be placed between the pump and the delivery valve.
The size of the valve should match the size of the pipe.
The delivery pipe should be sized to ensure a water velocity of about 2.5 m/s.
A dismantling joint should be provided between the pump and the valves to facilitate maintenance.

Driving Units

Driving units can be electric motors, or oil engines.
Electric motors are preferred due to their economical operation.
Stand-by power can be provided by an electric generator in case of power outages to ensure continuous pumping.
Oil engines can be used when power is not available.

Pumping Machinery Maintenance

A non-return valve at the discharge pipe, supplemented by a sluice valve, should never be closed while the pump is running.
A joint detailed inspection of the pumping machinery by Section Engineer (Works) should be conducted annually.
The pumping machinery should be inspected by the Assistant Engineer every three months.
Stock account showing transactions of stores should be maintained.
A log book for the filtration plant should be maintained.
The Divisional Engineer should inspect the water works in detail annually and record his notes in the Inspection Register.

Water Treatment Process

Coagulants (in dry powder or aqueous solution) should be added in the correct proportion based on the raw water turbidity.
Filters should be cleaned and washed with pure water at prescribed intervals.
Filtered water should be sterilized with liquid chlorine or bleaching powder to the specified dosage.
Disinfectants should be stored properly, and all safety precautions must be taken.

Water Works Staff Responsibilities

The staff in charge should strictly adhere to prescribed rules.
Detailed instructions on the operation of the plant and purification process should be available at every installation along with duty lists of staff.

Water Quality Standards

The standard for water quality should meet the requirements for drinking water specified in Indian Standard - Drinking water - specification (First Revision) IS:10500 - 1991 by BIS.

Water Supply Scheme Checklist

A checklist for water supply schemes should be used and maintained.
This checklist should include sections covering assessment of demand, source of water, and scheme approval details.

Water Supply Scheme Assessment of Demand

The checklist should verify whether the scheme is new or an augmentation of existing arrangements.
It should confirm that the total demand has been assessed, including domestic needs, workshops, offices, and station requirement.
The checklist should ensure that fire demand, if any, loss and wastages, and variations in demand have been considered.
The checklist should cover the characteristics of the water quality, including required and permissible limits.

Water Supply Scheme Source of Water

The checklist should ensure that the quantity/yield is sufficient to meet the requirement.
It should verify that tests for water quality have been performed.
The checklist should assess whether treatment is required to reduce impurities within the permissible range.
It should confirm that a sanitary survey has been conducted to estimate possible pollution or contamination from the source of water.
The checklist should verify that the line of treatment is consistent with the required water quality.
The checklist should assess whether the proposed source has accessibility.

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Description

This quiz explores the fundamentals of water supply systems, focusing on planning, demand assessment, and source evaluation. It delves into the specific requirements for maintaining water availability, especially in relation to railway operations and the use of open wells. Understanding these concepts is crucial for effective water management.