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Haryana BSEH Senior Secondary NSQF Plumbing study materials
Haryana BSEH Senior Secondary NSQF Plumbing study resources

Haryana BSEH Senior Secondary NSQF Plumbing practice questions

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Question 1Occupational Safety, Health and Hygiene in Plumbing Work

Before entering a newly installed underground drainage manhole to clear a blockage, which precaution is most important for preventing a fatal gas hazard?

  1. Wearing a cotton face mask and entering immediately after the cover is removed
  2. Entering quickly after splashing water on the chamber walls to settle the dust
  3. Testing the atmosphere for oxygen and toxic gases before entry and providing forced ventilation Correct answer.
  4. Carrying a lit candle to check whether the flame stays alive inside the chamber

Explanation

Confined spaces such as manholes and septic chambers can accumulate hydrogen sulphide, methane and carbon dioxide while oxygen is depleted, so the atmosphere must be tested with a calibrated multi-gas meter and ventilated before anyone enters. Entry is permitted only with a permit, a standby person and rescue arrangements. A physical test of the air is the only reliable way to confirm it is safe to breathe.

Question 2Occupational Safety, Health and Hygiene in Plumbing Work

A plumber must cut and thread galvanised steel pipe using a powered pipe-threading machine. Which practice best controls the risk of entanglement and cuts?

  1. Secure the pipe in the machine, keep guards in place and clear metal chips only after the machine stops Correct answer.
  2. Wear loose-sleeved overalls so the arms move freely near the rotating dies
  3. Remove the machine guard to see the dies clearly and keep the machine running while clearing chips
  4. Hold the pipe by hand instead of clamping it, so it can be released quickly if it binds

Explanation

Rotating pipe and threading dies can catch clothing and draw a hand into the machine, so the pipe must be clamped, guards kept fitted and chips removed with a hook or brush only after the spindle has stopped. Loose clothing and hand-holding defeat these controls. Clearing chips on a running machine is a common cause of severe hand injury.

Question 3Occupational Safety, Health and Hygiene in Plumbing Work

While soldering copper pipe with a lead-free solder and flux in a small bathroom, what is the main health precaution the plumber should take?

  1. Store the flux open beside the flame so it stays warm and flows better
  2. Work in a well-ventilated area and avoid breathing flux fumes, using local extraction where possible Correct answer.
  3. Seal the door and windows to keep the flame steady and prevent draughts
  4. Wear a full-face welding shield because the flame is brighter than an arc

Explanation

Soldering fluxes give off irritating and potentially harmful fumes, particularly in small enclosed rooms, so the work area needs ventilation or local exhaust extraction and the plumber should keep their head out of the plume. Flux containers must be kept closed and away from the flame. A welding shield is not the control for fume exposure.

Question 4Occupational Safety, Health and Hygiene in Plumbing Work

Which action best protects a plumber's hearing when using a hammer drill on a concrete wall for a long period?

  1. Place cotton wool loosely in the ear canals to soften the sound
  2. Rely on the natural ability of the ear to adjust after the first few minutes
  3. Wear ear defenders rated for the noise level and limit continuous exposure time Correct answer.
  4. Turn up music on earphones so the drill noise is masked

Explanation

Prolonged exposure to high noise levels from hammer drills causes permanent noise-induced hearing loss, so suitable hearing protection with an adequate attenuation rating should be worn and exposure duration limited. Cotton wool gives negligible attenuation and earphones add to the noise dose. The ear does not become protected by getting used to noise.

Question 5Occupational Safety, Health and Hygiene in Plumbing Work

A plumber must carry a length of 4-metre PVC pipe up an external ladder to a first-floor site. Which method is safest?

  1. Throw the pipe up to a colleague standing on the scaffold edge
  2. Carry the pipe vertically on the shoulder while climbing, without securing it
  3. Hoist the pipe by rope from the ground after climbing with both hands free, keeping the area below clear Correct answer.
  4. Climb with the pipe held under one arm so both hands are partly free

Explanation

Maintaining three points of contact on a ladder is essential, so long pipes should be hoisted separately by rope or lifted mechanically while the climber keeps both hands free, with the drop zone below controlled. Carrying or throwing long lengths creates falling-object and fall-from-height risks. The pipe should also be secured against wind once at height.

Question 6Occupational Safety, Health and Hygiene in Plumbing Work

When lifting a heavy cast-iron soil pipe fitting from the ground with another worker, which technique reduces the risk of back injury?

  1. Lift with a jerking motion to get the load moving quickly past the knees
  2. Keep the load close to the body, bend the knees, keep the back straight and lift smoothly with a coordinated team Correct answer.
  3. Bend at the waist with straight legs and twist the trunk while lifting
  4. Hold the load at arm's length so it does not touch the clothing

Explanation

Safe lifting keeps the load close to the body, uses the leg muscles with a straight back and avoids twisting, and a two-person lift must be coordinated so one person calls the lift. Holding a load at arm's length greatly increases the spinal load. Jerking and twisting are common causes of acute back injury.

Question 7Occupational Safety, Health and Hygiene in Plumbing Work

A plumber is using a two-part chemical drain-cleaning product in a blocked kitchen waste pipe. Which combination of controls is most appropriate?

  1. Wear gloves and eye protection, follow the manufacturer's dilution and never mix with other chemicals such as bleach Correct answer.
  2. Work without eye protection because the chemical is only poured into the drain
  3. Add bleach to the drain cleaner to improve the reaction and clear grease
  4. Mix the two parts in a closed bottle to build pressure for clearing the blockage faster

Explanation

Drain-cleaning chemicals are corrosive or strongly alkaline and can cause severe burns and eye injury, so gloves and goggles are needed, the product must be used exactly as directed, and it must never be mixed with other chemicals. Mixing an acid cleaner with bleach or an alkaline product can release toxic chlorine gas or cause a violent reaction. Sealed containers can rupture under gas pressure.

Question 8Occupational Safety, Health and Hygiene in Plumbing Work

Which is the correct way to store and use a compressed oxygen and fuel-gas set for brazing pipework on site?

  1. Grease the oxygen regulator threads to make the connection easier to tighten
  2. Store the fuel-gas cylinder next to the oxygen cylinder with the caps removed for quick use
  3. Lay both cylinders flat on the floor so they cannot topple and roll them to the work position
  4. Keep cylinders upright and secured, store oxygen and fuel gas apart, and use flashback arrestors on both hoses Correct answer.

Explanation

Compressed-gas cylinders must be kept upright and secured against falling, with oxygen and fuel gas separated and protected from ignition sources, and flashback arrestors fitted at the regulator or torch to stop a flame travelling back into the cylinder. Oil or grease on oxygen fittings can cause spontaneous ignition. Cylinders are never rolled or laid down for convenience.

Question 9Occupational Safety, Health and Hygiene in Plumbing Work

A plumber needs to work on a section of copper pipe that may still contain water and is connected to an electric immersion heater circuit. What is the correct first step before cutting the pipe?

  1. Wrap the pipe in insulating tape and cut it with a powered disc cutter
  2. Cut the pipe quickly with a hacksaw while a colleague holds a bucket underneath
  3. Isolate and lock off the electrical supply, drain the pipe and confirm it is depressurised before cutting Correct answer.
  4. Loosen the nearest compression fitting slightly to let water trickle out while cutting

Explanation

Before cutting into any pipework, the electrical supply to associated equipment such as immersion heaters and pumps must be isolated and locked off, and the section drained and proved depressurised. Cutting a live circuit or a pressurised pipe can cause electric shock, scalding or flooding. Insulating tape does not isolate a circuit.

Question 10Occupational Safety, Health and Hygiene in Plumbing Work

Which statement correctly describes the purpose of a permit-to-work system for plumbing work in a confined space such as a pump chamber?

  1. It replaces the need for a gas test because the signature confirms the space is safe
  2. It is only required when the chamber is more than three metres deep
  3. It is a formality that only records how long the job took after the work is finished
  4. It formally authorises the work, records the precautions taken and ensures the space is tested, ventilated and monitored with rescue arrangements in place Correct answer.

Explanation

A permit-to-work is a formal control that authorises specific work after precautions have been verified, records the isolation, atmosphere testing, ventilation and standby arrangements, and is closed out when the job ends. It supplements, but never replaces, gas testing and rescue planning. Depth alone is not the criterion for confined-space entry controls.

Question 11Occupational Safety, Health and Hygiene in Plumbing Work

A plumber is using a portable electric angle grinder to cut a cast-iron pipe on a wet site. Which measure most directly reduces the risk of electric shock?

  1. Stand on the wet ground in rubber sandals to insulate the feet
  2. Run the grinder from the nearest socket without checking whether it is RCD protected
  3. Hold the tool with one hand so the other hand can feel for current
  4. Use a residual current device (RCD) protected supply and inspect the tool and cable for damage before use Correct answer.

Explanation

Portable electric tools used in wet or damp conditions must be supplied through a residual current device that trips quickly on earth leakage, and the tool, plug and cable must be inspected for damage before use. Rubber sandals give no reliable insulation and one-handed use reduces control. An unprotected socket offers no additional protection against a fault.

Question 12Occupational Safety, Health and Hygiene in Plumbing Work

During excavation of a trench for an underground drainage line, which practice best prevents collapse injuries to workers in the trench?

  1. Enter the trench only briefly without shoring, because short exposure is harmless
  2. Keep excavated spoil and materials piled on the trench edge to save space on site
  3. Shore or batter the trench sides, keep spoil back from the edge and inspect the excavation regularly, especially after rain Correct answer.
  4. Rely on the trench being less than two metres deep as a guarantee against collapse

Explanation

Trench walls can collapse suddenly even at shallow depth, so the sides must be supported or battered back to a safe angle, spoil and materials kept clear of the edge to avoid surcharge loading, and the excavation inspected by a competent person at intervals and after rain. Brief entry into an unsupported trench is still a serious risk. Depth alone does not make a trench safe.

Question 13Occupational Safety, Health and Hygiene in Plumbing Work

Which practice is correct for handling and disposing of the debris and old materials removed while replacing a lead water service pipe?

  1. Keep lead offcuts in the tool bag with food and drinks for convenience
  2. Melt the lead on site to recover it and pour it into a mould without respiratory protection
  3. Burn the old lead pipe with general waste to reduce its volume
  4. Store lead offcuts in a labelled container, wash hands before eating and dispose of them through an authorised route Correct answer.

Explanation

Lead is a cumulative poison that enters the body by ingestion and inhalation, so offcuts must be kept in a labelled container, hands washed before eating or smoking, and waste consigned to an authorised disposal route. Burning or melting lead releases toxic fume. Storing lead with food creates a direct ingestion route.

Question 14Occupational Safety, Health and Hygiene in Plumbing Work

A plumber is preparing to use a gas torch to solder joints near a timber stud partition and a can of solvent cement. Which combination of controls is required?

  1. Starting work immediately and checking for smouldering after leaving the site the next day
  2. Opening the solvent cement can near the flame so the vapour disperses the heat
  3. A bucket of water only, placed three metres away from the work
  4. A fire watch, removal or shielding of combustibles, and a suitable fire extinguisher at hand Correct answer.

Explanation

Hot-work with a gas torch can ignite timber, dust and solvent vapours, so combustibles must be removed or protected with fire-resisting shields, a fire extinguisher kept immediately available and a fire watch maintained during and after the work. Solvent cement vapour is flammable and must never be released near a flame. Post-work checks are needed, not a next-day inspection only.

Question 15Occupational Safety, Health and Hygiene in Plumbing Work

Two plumbers are working in a plant room where a pump has been isolated for maintenance. Which arrangement best reflects the principle of lockout/tagout before work begins?

  1. The supervisor removes the fuse and keeps it in a pocket without telling anyone
  2. Each worker applies a personal lock to the isolation point and holds the only key, with a tag showing who is working Correct answer.
  3. A single padlock is shared and its key left in the plant room so anyone can restore power if needed
  4. The isolating switch is taped over with a paper notice, and the pump is restarted briefly to confirm it is working

Explanation

Lockout/tagout requires that each person working on the equipment applies their own lock and retains the key, so power cannot be restored while anyone is exposed, with tags identifying the person and the reason. A shared key or unrecorded fuse removal allows unexpected re-energisation. Restarting isolated equipment to test it while work is in progress is dangerous.

Question 16Occupational Safety, Health and Hygiene in Plumbing Work

A worker collapses inside a drainage manhole during a blockage-clearing job. Which immediate response is correct?

  1. Lower a rope to the casualty and ask them to tie it on themselves while waiting for the fire service
  2. Send a second worker down immediately without breathing apparatus to pull the casualty out
  3. Raise the alarm, keep others out, and perform a rescue using breathing apparatus and a harness with a retrieval line from outside the space Correct answer.
  4. Ventilate the manhole for two minutes and then enter without any respiratory protection

Explanation

Most fatalities in confined-space rescues involve would-be rescuers who enter without protection, so the correct response is to raise the alarm, prevent unprotected entry and carry out a rescue from outside using suitable breathing apparatus and a retrieval system. A collapsed casualty cannot be relied on to secure a rope. Short ventilation does not make an unknown atmosphere safe for entry.

Question 17Plumbing Tools, Materials and Pipe Fittings

Which material is most commonly specified for domestic hot and cold water supply piping because it resists corrosion and has a smooth bore?

  1. Asbestos cement
  2. Copper Correct answer.
  3. Cast iron
  4. Galvanised mild steel

Explanation

Copper is the standard choice for domestic hot and cold supply lines because it resists corrosion, tolerates heat, and its smooth bore keeps friction losses low. Galvanised steel, cast iron and asbestos cement are used for other services or are obsolete for this purpose.

Question 18Plumbing Tools, Materials and Pipe Fittings

A plumber needs a fitting to join two lengths of GI pipe in a straight run so the joint can be opened later for maintenance. Which fitting suits this requirement?

  1. Reducer
  2. Union Correct answer.
  3. Cap
  4. Elbow

Explanation

A union consists of three parts and allows a straight joint to be dismantled without cutting or unscrewing the pipe lengths on either side. An elbow changes direction, a reducer changes bore, and a cap closes a pipe end.

Question 19Plumbing Tools, Materials and Pipe Fittings

Which tool is used to cut an internal thread in a pipe fitting?

  1. Flaring tool
  2. Tap Correct answer.
  3. Die stock
  4. Pipe cutter

Explanation

A tap cuts internal threads, such as those inside a socket or fitting, while a die cuts external threads on pipe ends. Pipe cutters and flaring tools perform entirely different operations.

Question 20Plumbing Tools, Materials and Pipe Fittings

What is the standard purpose of a P-trap fitted below a wash basin?

  1. To increase water pressure at the outlet
  2. To support the weight of the basin
  3. To filter solid waste before it enters the drain
  4. To retain a water seal that blocks sewer gas Correct answer.

Explanation

The bend of a P-trap holds a small body of water that seals the pipe and prevents foul gases from the drainage system entering the room. The depth of the seal is what matters, not filtration, pressure or structural support.

Question 21Plumbing Tools, Materials and Pipe Fittings

Which pipe material is joined by solvent cement welding?

  1. uPVC Correct answer.
  2. Copper
  3. Lead
  4. Galvanised iron

Explanation

uPVC and CPVC pipes are joined with solvent cement, which softens the surfaces so they fuse into a continuous joint. GI, copper and lead are joined by threading, soldering or wiping respectively.

Question 22Plumbing Tools, Materials and Pipe Fittings

What does the nominal bore (NB) marked on a GI pipe indicate?

  1. A size designation close to, but not exactly, the internal diameter Correct answer.
  2. The outside diameter of the pipe in millimetres
  3. The maximum working pressure of the pipe
  4. The length of each standard pipe length

Explanation

Nominal bore is a size label used for reference and is only approximately equal to the internal diameter; actual outside diameter and wall thickness vary with the schedule. It is neither a length nor a pressure rating.

Question 23Plumbing Tools, Materials and Pipe Fittings

A hacksaw blade is being selected for cutting a thin-walled copper tube neatly. Which specification is most suitable?

  1. 6 teeth per inch blade
  2. 32 teeth per inch blade Correct answer.
  3. 24 teeth per inch blade
  4. 18 teeth per inch blade

Explanation

Fine-tooth blades of about 32 teeth per inch cut thin-walled tube cleanly because several teeth stay in contact with the wall and prevent snagging or tearing. Coarse blades catch on thin sections and deform the tube.

Question 24Plumbing Tools, Materials and Pipe Fittings

During threading, a plumber applies cutting oil to the pipe end. What is the main purpose of this oil?

  1. To increase the depth of thread cut by the die
  2. To cool and lubricate the die, giving cleaner threads and longer die life Correct answer.
  3. To soften the pipe so the die cuts more easily
  4. To seal the thread against leakage after assembly

Explanation

Cutting oil reduces friction and heat at the die, which produces cleaner threads and prolongs die life. Thread sealing is done later with jointing compound or tape, and oil does not change thread depth or soften steel.

Question 25Plumbing Tools, Materials and Pipe Fittings

A galvanised iron water main is being laid underground and the joint must resist corrosion in soil. Which jointing method is preferred?

  1. Solvent cement joint
  2. Butt weld without any coating
  3. Flared compression joint
  4. Screwed and socketed joint with jointing compound Correct answer.

Explanation

Underground GI mains are normally joined by screwing into sockets with jointing compound, and the joint is then protected against soil corrosion. Solvent cement does not act on steel, and a bare butt weld would corrode quickly.

Question 26Plumbing Tools, Materials and Pipe Fittings

A plumber must bend a 15 mm soft copper tube to a gentle offset without kinking it. Which method is correct?

  1. Fill it with dry sand and hammer it over a sharp edge
  2. Heat it to red heat and bend it over the knee
  3. Cut a wedge, bend the tube and braze the gap closed
  4. Bend it cold over a bending spring or internal bender Correct answer.

Explanation

Soft copper is bent cold using an external bending spring or an internal bending tool that supports the wall and prevents collapse. Sharp edges, excessive heat or cutting the wall would damage or weaken the tube.

Question 27Plumbing Tools, Materials and Pipe Fittings

A plumber is choosing a valve that must allow flow control in either direction and give a visible indication of whether it is open or closed. Which valve suits this best?

  1. Float valve
  2. Gate valve Correct answer.
  3. Check valve
  4. Pressure relief valve

Explanation

A gate valve is operated by a handwheel and its stem position shows whether the gate is open or shut, and it can be used for isolating flow in either direction. Check valves are one-way, relief valves are safety devices, and float valves respond to tank level.

Question 28Plumbing Tools, Materials and Pipe Fittings

Which fitting is used to connect a small-bore branch pipe to a larger main run without cutting the main into two pieces?

  1. Cross
  2. Tee
  3. Saddle clamp with ferrule Correct answer.
  4. Bend

Explanation

A saddle clamp fixed around the main with a ferrule allows a branch to be taken off without cutting the main run. A tee requires cutting the main, a cross makes a four-way junction, and a bend only changes direction.

Question 29Plumbing Tools, Materials and Pipe Fittings

A threaded GI joint leaks at the thread after assembly. Which is the most likely cause?

  1. The socket was made of uPVC
  2. Too few threads engaged because the pipe was under-threaded Correct answer.
  3. The jointing compound was applied to the outside of the socket
  4. The pipe was cut with a wheel cutter

Explanation

A screwed joint relies on a sufficient length of tapered thread engaging inside the socket with jointing compound to seal. Under-threading leaves too few engaged threads, so the joint cannot tighten and seal. The cutting method and the socket material do not cause this leak.

Question 30Plumbing Tools, Materials and Pipe Fittings

What is the purpose of a back-nut and socket arrangement on a low-pressure GI supply pipe?

  1. To provide a long screw connection that can be adjusted for alignment and dismantling Correct answer.
  2. To reduce the bore of the pipe at the joint
  3. To increase the flow velocity in the pipe
  4. To convert the pipe into a drain line

Explanation

A back-nut and socket combination gives a long screwed connection that can be adjusted and later dismantled for maintenance. It does not alter the bore or the hydraulic performance of the line.

Question 31Plumbing Tools, Materials and Pipe Fittings

Which statement correctly describes the difference between a coupling and a reducing socket?

  1. A coupling joins equal-bore pipes and a reducing socket joins different-bore pipes Correct answer.
  2. Both join equal-bore pipes but differ only in length
  3. A coupling is used only on copper and a reducing socket only on GI
  4. A coupling joins different-bore pipes and a reducing socket joins equal-bore pipes

Explanation

A coupling is a straight fitting for two pipes of the same nominal bore, while a reducing socket has different thread sizes at its two ends for pipes of unequal bore. Length and material do not define the difference.

Question 32Plumbing Tools, Materials and Pipe Fittings

A plumber is selecting a pipe material for a concealed hot water line operating at about 70 degrees Celsius. Which material is least suitable?

  1. uPVC Correct answer.
  2. PEX
  3. Copper
  4. CPVC

Explanation

uPVC softens and loses strength at elevated temperatures and is intended for cold water and drainage service. CPVC, PEX and copper are all rated for hot water at the stated temperature.

Question 33Plumbing Tools, Materials and Pipe Fittings

A drainage stack in a multi-storey building requires a fitting that allows a branch to enter at 45 degrees while maintaining smooth flow. Which fitting is appropriate?

  1. Straight coupling
  2. Blind flange
  3. 45 degree junction (Y-branch) Correct answer.
  4. Reducing bush

Explanation

A 45 degree junction, often called a Y-branch, brings a branch into the stack at a shallow angle so waste flows smoothly and the risk of blockage is reduced. Couplings, bushes and flanges do not create angled branches.

Question 34Plumbing Tools, Materials and Pipe Fittings

Which tool is used to check that a pipe end has been cut square before threading?

  1. Spirit level
  2. Try square Correct answer.
  3. Vice
  4. Pipe wrench

Explanation

A try square placed against the pipe end shows whether the cut face is at right angles to the axis; an out-of-square end causes the die to start crooked and produces a tapered thread. Levels, vices and wrenches do not check squareness of a cut.

Question 35Plumbing Tools, Materials and Pipe Fittings

During pressure testing of a newly installed concealed supply line, the test pressure is normally set at which value relative to working pressure?

  1. Equal to the working pressure
  2. Half the working pressure
  3. About one and a half times the working pressure Correct answer.
  4. Twice the working pressure for all pipe materials

Explanation

Concealed supply pipework is normally tested at roughly one and a half times the working pressure for a specified period so that joints are proved without over-stressing the material. Testing at half or exactly working pressure would not reveal weak joints.

Question 36Plumbing Tools, Materials and Pipe Fittings

A GI pipe run shows a pinhole leak at a threaded joint that was sealed with excessive jointing compound. Which explanation best accounts for the failure?

  1. Excess compound reacted with the zinc coating to form a hole
  2. Excess compound prevented the threads from fully engaging, leaving a loose joint Correct answer.
  3. The compound dissolved the pipe wall from outside
  4. The compound increased the bore pressure at the joint

Explanation

Jointing compound is a sealant, not a filler; a heavy excess stops the male and female threads from seating metal to metal, so the joint stays loose and weeps. Compound does not react with zinc to perforate the wall or dissolve steel.

Question 37Plumbing Tools, Materials and Pipe Fittings

A plumber must connect a copper tube to a GI pipe in a supply line. Which arrangement best avoids galvanic corrosion at the junction?

  1. Brass or dielectric union between the two metals Correct answer.
  2. Wrapping the joint with PTFE tape only
  3. Soldering the copper directly into the GI socket
  4. Direct metal-to-metal screwed connection

Explanation

Copper and galvanised steel are dissimilar metals, and direct contact in the presence of water sets up galvanic corrosion. A brass or dielectric union separates the metals and breaks the electrical path that drives the corrosion.

Question 38Plumbing Tools, Materials and Pipe Fittings

A drainage system uses a 100 mm soil pipe with a 75 mm branch. Which fitting is required at the junction?

  1. 75 mm bend
  2. 100 mm straight coupling
  3. 100 mm inspection bend
  4. 100 x 75 mm reducing junction Correct answer.

Explanation

A reducing junction has a 100 mm run with a 75 mm branch outlet, which is exactly what is needed when a smaller branch joins a larger soil stack. A straight coupling, a bend or an inspection bend makes no branch connection.

Question 39Plumbing Tools, Materials and Pipe Fittings

In a building where the supply pressure is high, a plumber fits a pressure-reducing valve downstream of the main. What is the main effect on the installation?

  1. It removes air from the supply line
  2. It acts as a non-return valve
  3. It raises the flow rate at every tap
  4. It limits downstream pressure to a set value and protects fittings Correct answer.

Explanation

A pressure-reducing valve holds the downstream pressure at an adjustable set value, protecting taps, cisterns and appliances from excessive pressure. It does not increase flow, de-aerate the line, or by itself prevent reverse flow.

Question 40Plumbing Tools, Materials and Pipe Fittings

A plumber has a choice of a wheel cutter and a hacksaw for cutting a 50 mm GI pipe that will be threaded. Why is the wheel cutter preferred?

  1. It work-hardens the pipe so threading is easier
  2. It cuts faster than a hacksaw but leaves a rough edge
  3. It removes the galvanised coating completely
  4. It leaves a square end with minimal burr, giving a better thread start Correct answer.

Explanation

A wheel cutter produces a square, clean cut with little burr, so the die starts true and cuts an even thread. A hacksaw cut is harder to keep square and leaves a rougher edge that can make the thread crooked.

Question 41Pipe Joining, Threading, Bending and Fixing Techniques

In NSQF plumbing practice, which tool is used to cut an external thread on a galvanised iron pipe?

  1. Pipe cutter wheel
  2. Flaring block
  3. Reamer
  4. Die stock with a pipe die Correct answer.

Explanation

A die stock holds the pipe die and cuts the external thread on the pipe end. The pipe cutter scores and severs the pipe, the reamer removes the internal burr, and a flaring block forms a flare on soft copper. Threading therefore requires the die and its stock.

Question 42Pipe Joining, Threading, Bending and Fixing Techniques

After cutting a GI pipe with a pipe cutter, why must the bore be reamed before threading?

  1. To make the pipe end perfectly square to its axis
  2. To remove the internal burr that restricts flow and damages the die Correct answer.
  3. To increase the wall thickness at the pipe end
  4. To soften the metal so the die cuts more easily

Explanation

The cutter wheel pushes metal inward, leaving a raised burr inside the bore. This burr narrows the waterway, traps debris, and can catch the die and tear the thread. Reaming restores a clean bore before threading.

Question 43Pipe Joining, Threading, Bending and Fixing Techniques

Which thread form is the standard taper thread used on GI water supply pipes in Indian practice?

  1. Metric coarse thread
  2. Unified fine thread
  3. Square thread
  4. BSP taper thread Correct answer.

Explanation

Water and gas pipes in Indian practice use the British Standard Pipe taper thread, which seals by wedging into a matching internal taper. Metric, unified, and square threads are used on fasteners or machine parts, not on pipe joints.

Question 44Pipe Joining, Threading, Bending and Fixing Techniques

What is the purpose of applying a thin coat of linseed oil or cutting oil while threading a GI pipe?

  1. To seal the thread against leakage
  2. To make the die cut a deeper thread
  3. To prevent the pipe from rusting after installation
  4. To lubricate and cool the die, giving cleaner threads Correct answer.

Explanation

Cutting oil reduces friction and heat between the die and the pipe, which produces smoother threads and longer die life. It is not a jointing compound and does not affect the depth of thread cut.

Question 45Pipe Joining, Threading, Bending and Fixing Techniques

In a socket joint of GI pipe, what is the correct sequence for making the joint?

  1. Apply compound to the socket, then force the plain pipe end into it
  2. Thread the pipe, apply jointing compound on the male thread, and screw into the socket Correct answer.
  3. Wrap the socket externally with tape and push the pipe in
  4. Weld the pipe end into the socket without threading

Explanation

A screwed socket joint relies on the tapered external thread engaging the internal thread, with jointing compound or PTFE tape on the male thread to seal the spiral gap. The pipe must be threaded; a plain end cannot hold in a socket.

Question 46Pipe Joining, Threading, Bending and Fixing Techniques

Which fitting is used to join two pipes of different diameters in a straight run?

  1. Reducer socket Correct answer.
  2. Union
  3. Tee
  4. Elbow

Explanation

A reducer socket has one end sized for the larger pipe and the other for the smaller pipe, allowing a straight change of diameter. An elbow changes direction, a tee branches the line, and a union allows dismantling.

Question 47Pipe Joining, Threading, Bending and Fixing Techniques

Which bending method is suitable for bending a GI pipe without filling it with sand?

  1. Heating to white heat and striking with a hammer
  2. Rotary or roll bending on a pipe bender with a forming shoe Correct answer.
  3. Cold bending with no support at all
  4. Hammer bending over a bare knee

Explanation

A pipe bender with a forming shoe supports the walls and bends the pipe progressively around a controlled radius, limiting ovality and wrinkling. Unsupported methods such as hammering over a knee collapse the bore and kink the wall.

Question 48Pipe Joining, Threading, Bending and Fixing Techniques

What does the term 'making off' a pipe joint mean on site?

  1. Removing the protective coating from the pipe
  2. Completing and tightening the joint so it is ready for testing Correct answer.
  3. Marking the pipe for bending
  4. Cutting the pipe to its final length

Explanation

Making off means finishing the joint assembly, tightening it to the correct engagement, and cleaning off surplus compound so it is ready for pressure testing. Cutting, marking, and coating removal are separate preparatory operations.

Question 49Pipe Joining, Threading, Bending and Fixing Techniques

A plumber threads a 25 mm GI pipe and finds the thread is stripped and shallow. Which cause is most likely?

  1. The cutting oil was applied generously
  2. The pipe was reamed too deeply
  3. The pipe vice was tightened firmly
  4. The die was worn or the pipe was undersized for the die setting Correct answer.

Explanation

Shallow, torn threads usually indicate a worn or badly adjusted die, or a pipe whose outside diameter is below the die's range. Reaming, lubrication, and vice grip do not affect thread depth in this way.

Question 50Pipe Joining, Threading, Bending and Fixing Techniques

Why is it important to avoid over-tightening a screwed GI joint?

  1. It reduces the flow through the pipe
  2. It makes the joint impossible to paint
  3. It can split the socket or crack the pipe wall Correct answer.
  4. It changes the thread from taper to parallel

Explanation

Excessive torque on a taper thread wedges the male end too far into the socket, generating hoop stress that can split the fitting or crack the pipe. Flow, paint adhesion, and thread form are not affected by tightening force.