Types of Pipes and Trench Depths for Sewerage
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Questions and Answers

What type of motors should be used in locations where there is a risk of igniting inflammable gases?

  • Electric motors
  • Weatherproof and flame-proof diesel engines (correct)
  • Hybrid motors
  • Standard gasoline engines

    • What is the minimum distance that engines should be placed from openings in relation to wind direction?

  • 3 meters
  • 4 meters
  • 1 meter
  • 2 meters (correct)

    • What is the recommended width of the trench for a pipe diameter of 20 cm laid at a depth of 110 cm?

  • 60 cm
  • 50 cm (correct)
  • 70 cm
  • 40 cm

    • What type of ventilation is suggested for manholes to aid in displacing flammable gases?

    <p>Forced ventilation with a blower</p> Signup and view all the answers

    What should happen to any obstructions found in stormwater drains during the periodical cleaning process?

    <p>They should be removed with drain cleaning tools</p> Signup and view all the answers

    What is the primary purpose of the underground masonry tank in aqua privy latrines?

    <p>To facilitate anaerobic digestion</p> Signup and view all the answers

    What type of pipes are suitable for use in unstable or made-up grounds?

    <p>Cast Iron Pipes</p> Signup and view all the answers

    What should be used to ensure the covers of inspection chambers are properly replaced?

    <p>Bedding in suitable grease or other materials</p> Signup and view all the answers

    What is the recommended minimum water seal above the crown level of the inlet pipe in the digestion tank?

    <p>50mm</p> Signup and view all the answers

    Which of the following pipes is not suitable for carrying acid effluents or sewage under certain conditions?

    <p>Unplasticised PVC Pipes</p> Signup and view all the answers

    What is the recommended slope of the pipelines from the collection chamber to the digester?

    <p>1 in 20</p> Signup and view all the answers

    For pipe installations in basements or crossings of water courses, which pipe type is particularly useful?

    <p>Cast Iron Pipes</p> Signup and view all the answers

    What should be done with any pipes or drains leading to drainage sumps after the work is completed?

    <p>They should be filled with sand and consolidated.</p> Signup and view all the answers

    How frequently should the settled sludge at the bottom of the digestion tank be cleared?

    <p>Once in two years</p> Signup and view all the answers

    What should be avoided in the water closet of bio-latrines to maintain efficiency?

    <p>Water taps</p> Signup and view all the answers

    What is the minimum total width of the trench at the top for a depth exceeding 90 cm?

    <p>75 cm</p> Signup and view all the answers

    Which of the following materials is commonly used for house drainage systems?

    <p>Asbestos Cement</p> Signup and view all the answers

    What is the maximum amount of water recommended per capita for flushing in bio-latrines?

    <p>1.5 to 2 litres</p> Signup and view all the answers

    Which of the following is typically not a component of an aqua privy latrine?

    <p>Underwater toilets</p> Signup and view all the answers

    What is the added width of the trench for pipe diameters laid at depths greater than 120 cm?

    <p>40 cm</p> Signup and view all the answers

    What should be considered when determining the plinth level of latrines?

    <p>Invert level of the outlet pipe</p> Signup and view all the answers

    What happens to the effluent from aqua privy latrines after digestion?

    <p>It is absorbed through sub-surface irrigation</p> Signup and view all the answers

    In combined digesters, where does the sewage flow first after collection?

    <p>To a chamber attached to each water closet</p> Signup and view all the answers

    What type of toilet systems are approved for use on the Railways?

    <p>Flush toilets with septic tank systems</p> Signup and view all the answers

    What must be kept in sufficient detail and accuracy for sewer location?

    <p>Records of the location and depth of all sewers</p> Signup and view all the answers

    How frequently should sewer line gangs clean and flush sewers?

    <p>At least twice every month</p> Signup and view all the answers

    What is the minimum retention time required for digestion in septic tanks?

    <p>30 days</p> Signup and view all the answers

    What must be ensured during the design of a sewerage system?

    <p>Maintenance requirements</p> Signup and view all the answers

    What is a requirement for the maintenance of open sullage drains?

    <p>Cleaning should be done at least twice a month</p> Signup and view all the answers

    What should be done to soak-pits to ensure they are effective?

    <p>Dug up and cleaned at least once a month</p> Signup and view all the answers

    What type of toilets require sanitation according to the guidelines?

    <p>Dry (Service type) toilets</p> Signup and view all the answers

    What should be done to manholes prior to entry by personnel?

    <p>Leave them open for gas to escape</p> Signup and view all the answers

    What is the purpose of converting septic tanks into digesters?

    <p>To minimize flushing for effective digestion</p> Signup and view all the answers

    What should be done to ensure safety before workers enter a gully trap?

    <p>Gas tests should be repeated and the atmosphere cleared.</p> Signup and view all the answers

    Which department is responsible for conservancy arrangements?

    <p>Any of the Medical, Operating, or Engineering Departments</p> Signup and view all the answers

    When should irregularities in the working of the conservancy arrangements be reported?

    <p>Promptly when noticed</p> Signup and view all the answers

    What precaution should be taken if gas or oxygen deficiency cannot be ventilated adequately?

    <p>Workers must wear masks and avoid sources of ignition.</p> Signup and view all the answers

    What is the main purpose of maintaining adequate ventilation during work?

    <p>To minimize the risk of toxic gas build-up.</p> Signup and view all the answers

    What action is necessary if dangerous gases are detected in a sewer?

    <p>Artificial ventilation methods must be employed.</p> Signup and view all the answers

    Why should gas tests be repeated frequently?

    <p>To ensure the atmosphere remains safe.</p> Signup and view all the answers

    What is a crucial step before allowing workers into deep manholes or sewers?

    <p>Training in oxygen hose equipment use.</p> Signup and view all the answers

    In what circumstance should masks be mandatory for workers?

    <p>If there is any indication of gas or oxygen deficiency.</p> Signup and view all the answers

    What is the recommended action for handling sources of ignition while working in a hazardous area?

    <p>All sources of ignition must be avoided.</p> Signup and view all the answers

    What is primarily conveyed by a sewer system?

    <p>Sewage and other water-borne wastes</p> Signup and view all the answers

    Which of the following does not fit the definition of 'drain'?

    <p>A system for clean water distribution</p> Signup and view all the answers

    In the context of drainage and sewerage, what does 'sewerage' refer to?

    <p>The collection and conveyance of sewage</p> Signup and view all the answers

    Which of the following codes or practices would provide guidelines for building drainage?

    <p>IS 1742: 1983</p> Signup and view all the answers

    What defines a 'drainage' system?

    <p>A network for removing unwanted liquids</p> Signup and view all the answers

    Which of the following is an essential component of sewage management systems?

    <p>Septic tanks</p> Signup and view all the answers

    What is the definition of a 'manhole' in sewage systems?

    <p>An access point for sewer maintenance</p> Signup and view all the answers

    What is the primary function of the IS 1172: 1983 standard?

    <p>Code for water supply requirements</p> Signup and view all the answers

    What is a critical precaution for workers descending into a manhole shaft?

    <p>Test each ladder step carefully</p> Signup and view all the answers

    What type of lighting is recommended for work in environments with hazardous gases?

    <p>Gas-proof electric lighting</p> Signup and view all the answers

    Which method is vital for ensuring a safe work environment in sewer manholes?

    <p>Using non-sparking tools</p> Signup and view all the answers

    How often should the presence of noxious gases be tested in sewer manholes?

    <p>At the start and end of each shift</p> Signup and view all the answers

    What precaution should be taken regarding obstructed access plates in gullies?

    <p>Remove and flush out the traps thoroughly</p> Signup and view all the answers

    What is the minimum slope required for the pan in bio-latrines?

    <p>40 degrees</p> Signup and view all the answers

    What type of grating should be installed before the entry of water into the digesters to prevent foreign matter?

    <p>25-50 mm spaced grating</p> Signup and view all the answers

    What is the minimum retention period required for anaerobic digestion?

    <p>30 days</p> Signup and view all the answers

    Which characteristic of effluent indicates satisfactory functioning of anaerobic digesters?

    <p>Effluent is odourless</p> Signup and view all the answers

    What should not be mixed with the water in the toilet pan to prevent issues?

    <p>Foreign matter like garbage</p> Signup and view all the answers

    What is the preferred method of flushing in non-residential toilets?

    <p>Coach handles for controlled water release</p> Signup and view all the answers

    What must be ensured about the outlet drains in anaerobic digesters?

    <p>They should have proper slope and rounded corners</p> Signup and view all the answers

    What is a characteristic of effluent from septic tanks compared to digesters?

    <p>It undergoes primary treatment for only 2-7 days</p> Signup and view all the answers

    How should ventilation be addressed in bio-latrines?

    <p>Adequate ventilation should be provided</p> Signup and view all the answers

    What is crucial for ensuring effective waste disposal systems?

    <p>Design with prevention of pollution in mind</p> Signup and view all the answers

    What type of toilet system should be used where an underground sewerage system can be connected during a water shortage?

    <p>Flush type toilets with modern cisterns</p> Signup and view all the answers

    In situations where an underground sewerage system is not available, what is the recommended toilet system for built-up areas?

    <p>Bio-latrines</p> Signup and view all the answers

    What type of flushing mechanism is advised against for urinals?

    <p>Automatic flushing cisterns</p> Signup and view all the answers

    What type of toilet system is suggested for roadside stations with limited population?

    <p>Bio-latrines or septic tanks</p> Signup and view all the answers

    Which type of toilet is approved for use in railway sanitation systems?

    <p>Standard flush toilets</p> Signup and view all the answers

    What guidelines must be followed regarding fire hydrants and sewer flushing?

    <p>Sewers may be flushed using the nearest fire hydrant if accessible</p> Signup and view all the answers

    Which type of toilet system should be avoided in areas with no water supply?

    <p>Standard flush toilets</p> Signup and view all the answers

    Which toilet flushing mechanism is recommended to ensure usage of less water?

    <p>Low-volume cisterns</p> Signup and view all the answers

    What primarily determines the size of a sanitary sewer system?

    <p>The projected population and per capita sewage</p> Signup and view all the answers

    What is the recommended approach for sanitizing toilets in railway systems?

    <p>Sanitize on a top priority program basis</p> Signup and view all the answers

    Which of the following is essential for ensuring suspended solids do not block a sewer?

    <p>Achieving a minimum self-cleansing velocity</p> Signup and view all the answers

    What is indicated by the invert and crown gradient lines in sewer profiles?

    <p>The proposed sewer lines along with necessary gradients</p> Signup and view all the answers

    What is the recommended range for velocity of flow in stormwater sewer systems?

    <p>1 to 2 meters per second</p> Signup and view all the answers

    What factors should be considered when estimating the quantity of sewage?

    <p>Future population growth and per capita sewage generation</p> Signup and view all the answers

    What does the self-cleansing velocity primarily depend on?

    <p>The particle size and specific weight of solids</p> Signup and view all the answers

    Which statement is true regarding stormwater and sanitary sewers?

    <p>Stormwater should never enter sanitary sewer systems</p> Signup and view all the answers

    In determining the alignment for sewer installation, what is accurately prepared?

    <p>A survey plan showcasing ground levels and soil conditions</p> Signup and view all the answers

    What should be done to ensure that large volumes of stormwater are effectively managed?

    <p>Designing independent stormwater sewer systems</p> Signup and view all the answers

    What role do peak and average flows play in the sizing of sanitary sewers?

    <p>They are critical for understanding overall system load</p> Signup and view all the answers

    Study Notes

    Types of Pipes for Sewerage Systems

    • Cast Iron Pipes: Suitable for unstable ground, made-up ground, and situations where pipes are suspended, like basements or crossings of water courses. They can handle high velocity (2.4 m/s) flows.
    • Asbestos Cement Pipes: Commonly used for house drainage systems. Not recommended for underground situations or for carrying acid effluents or sewage in conditions that promote hydrogen sulfide production.
    • PVC Pipes: Unplasticised PVC pipes can be used for drainage purposes.

    Trench Width and Depth for Sewer Pipes

    • Depth up to 120 cm: Trench width = Diameter of pipe + 30 cm
    • Depth above 120 cm: Trench width = Diameter of pipe + 40 cm
    • All depths exceeding 90 cm: Total width of trench at the top must be at least 75 cm.

    Trench Considerations

    • Support: All pipes, ducts, cables, mains, and other services exposed in the trench should be supported with timber and/or chain or rope slings.
    • Drainage Sumps: Sumps should be located outside the trench or at the sides of manholes. Pipes leading to sumps should be filled with sand after work completion.

    Laying of Sewer Pipes

    • Excavation: Follow construction safety practices. Remove surface earth containing grass roots and decaying vegetable matter before laying pipes.
    • Laying: Lay pipes according to good practice. Not suitable in areas where water tables are high or ground slopes are flat.

    Aqua Privy Latrines

    • Components: Underground masonry tank with latrine pans fixed on top. Pan outlet is 7.5 to 10 cm below the flow line in the tank.
    • Operation: Excreta is digested in the masonry tank and cleared through a manhole. Effluent can be absorbed through sub-surface irrigation or alternative means.
    • Flow: Gravity flow from the toilet to the digester is required.
    • Combined Digesters: Sewage collects in a chamber attached to each water closet and then flows to a combined digester.
    • Slope: Pipe slope from the collection chamber to the digester should be at least 1:20.
    • Water Seal: A 50 mm water seal above the inlet pipe's crown level should be maintained in the digestion tank.
    • Plinth Level: Determined working backwards from the invert level of the digestion tank outlet pipe.
    • Sludge Removal: Sludge at the bottom of the digestion tank should be cleared every two years.

    Bio-Latrines

    • Purpose: Improved aqua privies for managing small to larger quantities of sewage.
    • Water Requirement: Need 1.5 to 2 liters per capita for flushing.
    • Design: Standard drawings available from RDSO.
    • Key Considerations: No water tap should be provided in the water closet to avoid digester flooding.

    Approved Toilet Systems for Railways

    • Flush Toilets with Underground Sewerage: Approved system.
    • Flush Toilets with Septic Tank Systems: Must be equipped with soakpits/filter-beds for effluent.
    • Bio- Latrines: Approved system.
    • Aqua Privy Latrines: Approved system.
    • Dry Toilets: All service type toilets should be sanitized.
    • Septic Tanks: Should be fitted with prescribed soakpit/filter-bed or converted to digesters.

    Conservancy and Sanitary Arrangements

    • Responsibility: Handled by Medical, Operating, or Engineering Departments.
    • Irregularities: Report any problems promptly to the responsible officials.

    Maintenance of Sewerage System

    • Design: Consider maintenance requirements during design.
    • Ventilation: Provide adequate ventilation to minimize gas hazards. Open manholes regularly to allow gas escape.
    • Gully Traps: Examine and replace these regularly.
    • Sewer Cleaning: Cleaning and flushing should occur at least twice a month or more often if needed.
    • Records: Keep detailed and accurate records about sewer locations and depths.
    • Sewer Line Gangs: Responsible for cleaning and flushing sewers at least twice a month. Open manholes for a few hours to allow gas escape before entry.
    • Manhole Entry: Use masks and oxygen hose equipment if dangerous gas or oxygen deficiency is present. Do not flush gully deposits into the system.
    • Defects: Repair any defects found during inspection or tests.
    • Inspection Chambers & Gullies: Replace covers and bed them in grease or suitable materials.
    • Painting: Paint ladders, rings in deep manholes and manhole covers with approved paints.

    Open Sullage Drains

    • Maintenance: Maintain in good condition. Clean and flush at least twice a month or more frequently.
    • Soak-Pits: Clean soak-pits at least once a month and fill with fresh broken stones, bricks, or cinder.

    Covered Stormwater Drains

    • Maintenance: Periodically rodded using drain rods and a rubber or leather plunger. Flush with clean water after rodding. Remove any obstructions.

    Drainage & Sewerage

    • References : For information regarding plumbing services, drainage, and sanitation, refer to the National Building Code of India (1983), relevant BIS Codes, and the Ministry of Urban Development's Manual on Sewerage and Sewage Treatment.
    • Drainage System: Designed separately from sanitary sewers.
    • Types of Sewers:
      • Drain: For stormwater or wastewater.
      • Sewer: Carries sewage or other water-borne waste.
      • Sanitary Sewer: Exclusively for sewage.
      • Stormwater Sewer: Dedicated to stormwater drainage.
    • Factors that influence sanitary sewer size:
      • Amount of sewage.
      • Peak & average flow variation.
      • Limiting flow velocities.
      • Area's topography.
      • Construction materials.
    • Factors that influence stormwater sewer size:
      • Stormwater runoff.
      • Optimal flow velocity.
      • Construction materials.
    • Alignment of Sewers:
      • Determined from a site survey plan at a scale of 100 meters to 1 cm.
      • Plan shows the proposed sewer lines, ground levels, and soil conditions for establishing grades and cost estimation.
      • Profiles show the invert and crown gradient lines.
    • Velocity of Flow:
      • Maintain minimum velocity of 1 meter per second and a maximum of 2 meters per second.
      • On steep slopes, drop manholes may be required.
    • Self-Cleansing Velocity:
      • Important to avoid sediment build-up and blockages.
      • Depends on particle size and specific weight of suspended solids.

    Anaerobic Digesters

    • Indicators of Satisfactory Performance:
      • Odorless effluent.
      • No attraction to flies or mosquitos.
      • Effluent pH not lower than 7.0.

    Toilet Systems

    • Conservation of Water:
      • Importance of water conservation due to scarcity in India.
      • Proper maintenance of water closet flushing systems.
      • Use of "coach" handles in toilets for controlled water usage.
      • Use of dripping ferrules in urinals instead of automatic flushing cisterns.
    • Recommended Toilet Systems:
      • Sewerage System Available:
        • Flush type toilets with low-flow cisterns.
        • "Coach" handle flushing for residential and non-residential toilets.
      • No Sewerage System Available:
        • Bio-latrines in built-up areas or where soak pits/filter beds are not feasible.
        • Bio-latrine or septic tank system with coach handles in sparsely inhabited areas.
      • Urinals:
        • Use of dripping ferrules instead of automatic flushing cisterns.

    Sewer Maintenance

    • Sewage Blockage Removal:
      • Use of firehose from nearby hydrant for flushing.
      • Rodding from the next manhole.
      • Use of permitted safety lights (not ordinary flashlights), rubber boots, and non-sparking tools for safety.
    • Manhole Inspections:
      • Two workers available for assisting anyone descending deep manholes.
      • Careful ladder step inspection.
      • Portable air blowers for ventilation in manholes with potential noxious gases.
    • General Cleaning:
      • Clean and remove blockage with appropriate tools.
      • Flush the system thoroughly after cleaning.
      • Clean gullies by removing access plates, plunging, and flushing with clean water.

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    Description

    This quiz explores various types of pipes used in sewerage systems, including cast iron, asbestos cement, and PVC pipes. It also covers trench width and depth specifications essential for proper installation. Test your knowledge on these critical components of sewerage construction.

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