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Maharashtra HSC NSQF Plumber General II study materials
Maharashtra HSC NSQF Plumber General II study resources

Maharashtra HSC NSQF Plumber General II practice questions

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Question 1Occupational Safety, Health and Working Environment

On a plumber's site, which PPE item is specifically required when working inside a freshly laid sewer manhole where hydrogen sulphide may be present?

  1. A high-visibility vest only
  2. A welding shield
  3. A respirator with suitable gas-filter cartridges or supplied air Correct answer.
  4. Leather palm gloves only

Explanation

Confined spaces such as manholes can accumulate hydrogen sulphide, which is toxic and deadens the sense of smell at higher concentrations. Respiratory protection matched to the hazard, plus gas testing before entry, is the control that addresses the inhalation risk directly. Other PPE does not protect the lungs.

Question 2Occupational Safety, Health and Working Environment

A plumber must cut a cast-iron soil pipe with a powered cut-off saw. Which combination best reflects the required eye and face protection?

  1. Safety goggles plus a face shield over them Correct answer.
  2. No eye protection if the cut is short
  3. A single-lens sun shade
  4. Ordinary prescription spectacles

Explanation

Powered cutting of cast iron throws high-velocity fragments and dust, so impact-rated goggles are needed and a face shield adds coverage for the whole face. Everyday prescription spectacles are not impact rated and leave the sides open. Short cuts still generate flying particles.

Question 3Occupational Safety, Health and Working Environment

What is the primary purpose of shoring or trench-box support in a plumber's excavation for an underground drainage line?

  1. To keep the trench dry during rain
  2. To reduce the amount of bedding sand needed
  3. To prevent soil collapse that could bury or crush workers Correct answer.
  4. To improve the appearance of the site

Explanation

Excavation walls can collapse suddenly and the soil weight can crush or suffocate a worker within seconds. Shoring, benching or a trench box is installed to resist that collapse and protect anyone working below. Dewatering and bedding are separate concerns.

Question 4Occupational Safety, Health and Working Environment

Before entering a septic tank or deep inspection chamber, what should be done first?

  1. Send in the newest worker to check conditions
  2. Light a match to check for gas
  3. Start the suction pump while a worker is inside
  4. Test the atmosphere for oxygen and toxic gases and arrange confined-space controls Correct answer.

Explanation

Atmospheric testing for oxygen deficiency and toxic or flammable gases must precede entry, followed by ventilation and a standby person. Never use a flame to test for gas because it can ignite the atmosphere. Untrained workers must not be sent in first.

Question 5Occupational Safety, Health and Working Environment

A plumber is using a solvent cement to join PVC pipes in a small toilet. Which control is most appropriate for the vapour hazard?

  1. Wear a dust mask
  2. Close all windows to keep dust out
  3. Work faster so exposure time is shorter
  4. Keep the door and window open and use local ventilation or a fan Correct answer.

Explanation

Solvent cements release volatile organic vapours that can irritate the eyes and respiratory tract and are flammable. Diluting them with cross-ventilation or local exhaust is the standard control in small rooms. A dust mask does not stop solvent vapour.

Question 6Occupational Safety, Health and Working Environment

What does the term 'toolbox talk' mean in the context of a plumbing work site?

  1. A written purchase order for hand tools
  2. A lecture given only to apprentices at the end of a project
  3. A short briefing at the start of work covering the day's hazards and safe methods Correct answer.
  4. An inspection of the toolbox contents for theft

Explanation

A toolbox talk is a brief, regular safety briefing held at the workplace before or during the shift. It covers the specific hazards of the planned tasks, the controls to use and any changes since the last briefing. It is not an inventory check or a formal lecture.

Question 7Occupational Safety, Health and Working Environment

A plumber must lift a heavy cast-iron bath to move it across a room. Which practice best protects the lower back?

  1. Bend at the waist and twist while lifting
  2. Lift with straight legs and a rounded back
  3. Lift quickly to reduce the time under load
  4. Keep the load close, bend the knees and lift with the legs, and get help if it is too heavy Correct answer.

Explanation

Manual handling injuries to the back are reduced by keeping the load close to the body, maintaining a neutral spine, bending the knees and using leg muscles. Twisting or jerking while loaded sharply increases spinal stress. If the load exceeds safe limits, mechanical aids or a second person should be used.

Question 8Occupational Safety, Health and Working Environment

A plumber is about to solder copper pipe joints indoors with a gas torch. Which combination of precautions is required?

  1. Fire extinguisher nearby, combustible material removed, and hot-work permit where required Correct answer.
  2. Nothing extra, because solder is not hot enough to ignite materials
  3. Only a bucket of water kept nearby
  4. Windows closed to avoid draughts affecting the flame

Explanation

Soldering involves an open flame and hot pipe surfaces, so combustible materials must be cleared or protected, a suitable extinguisher kept ready, and a hot-work permit obtained where the site requires it. Solder melts at temperatures well above the ignition point of many common materials.

Question 9Occupational Safety, Health and Working Environment

Which is the correct way to store a compressed gas oxygen cylinder on a plumbing site?

  1. Keep it loose so it can be moved quickly in an emergency
  2. Lay it horizontally on the ground near the welding area
  3. Store it in a locked wooden cupboard with solvent cements
  4. Store it upright, secured against falling, away from heat and oil, with the valve cap fitted when not in use Correct answer.

Explanation

Oxygen cylinders must stand upright and be chained or otherwise secured so they cannot fall and shear the valve. They should be kept away from heat sources and from oil or grease, which can ignite in the presence of oxygen. The valve protection cap is fitted when the cylinder is not connected.

Question 10Occupational Safety, Health and Working Environment

A worker using a drain-cleaning machine notices the cable beginning to whip. What is the safest immediate action?

  1. Pour water on the cable
  2. Increase speed to clear the blockage quickly
  3. Grip the cable firmly with a gloved hand to steady it
  4. Release the foot pedal or switch off the machine and step back Correct answer.

Explanation

A whipping or kinking drain cable can cause severe lacerations and entanglement, so the power source must be released immediately and the operator should step clear. Gloved hands must never be used to grab a rotating cable because gloves can be pulled in. The blockage should then be reassessed using the proper technique.

Question 11Occupational Safety, Health and Working Environment

Which of the following best describes the safe practice for using a portable electric angle grinder on a wet bathroom floor?

  1. Use it plugged into any nearby socket
  2. Barefoot contact with the wet floor is acceptable if the work is short
  3. Use a residual current device and keep the tool and leads clear of water Correct answer.
  4. Hold the tool with one hand to keep the other free

Explanation

Water on the floor greatly increases the risk of electric shock, so an RCD must protect the circuit and the tool and leads must be kept out of water. Both hands should be used to control the grinder firmly. Barefoot work on a wet floor removes a key layer of protection.

Question 12Occupational Safety, Health and Working Environment

A plumber finds an unlabelled container of clear liquid in the site store. What is the correct action?

  1. Use it as a pipe cleaner if it looks like solvent
  2. Pour a little on the floor to see how it reacts
  3. Treat it as unknown and report it to the supervisor for proper identification and labelling Correct answer.
  4. Smell it to identify the contents

Explanation

Unlabelled containers are a common cause of chemical exposure because the contents cannot be assumed. The safe response is to leave it alone, keep it closed and report it so it can be identified and labelled or disposed of properly. Smelling or testing unknown chemicals risks serious injury.

Question 13Occupational Safety, Health and Working Environment

Why is a permit-to-work system used for certain plumbing tasks such as entering a sewer or working on a live gas line?

  1. To allow workers to skip the toolbox talk
  2. To formally authorise a high-risk task after confirming controls are in place Correct answer.
  3. To replace the need for personal protective equipment
  4. To record the number of hours worked for payroll

Explanation

A permit-to-work is a formal written authorisation issued only after the hazards have been assessed and the controls confirmed, such as isolation, gas testing and standby arrangements. It does not replace PPE or briefings and is not a payroll record. It creates accountability for high-risk work.

Question 14Occupational Safety, Health and Working Environment

A plumber is working alone in a remote pump room. Which arrangement best reduces the risk if they are injured and cannot call for help?

  1. Leave the door open so someone may notice
  2. Work faster to finish before any incident
  3. Rely on a mobile phone with no signal check
  4. Arrange a lone-worker check-in schedule and confirm communication coverage before starting Correct answer.

Explanation

Lone working requires planned communication so that someone notices if the worker fails to check in. Confirming signal coverage and setting a call-in schedule with an escalation step provides that safety net. Leaving a door open is not a reliable alerting method.

Question 15Occupational Safety, Health and Working Environment

Which statement correctly describes the purpose of a safety data sheet (SDS) for a plumbing chemical such as a drain acid?

  1. It is the invoice for purchasing the chemical
  2. It lists only the price and pack size
  3. It is a marketing document describing product benefits
  4. It provides hazard, handling, first-aid and spill-response information for the substance Correct answer.

Explanation

An SDS is the standard source of information on the hazards of a substance and the controls needed, including first aid, spill response, storage and PPE. It is not a sales or commercial document. Workers should consult it before using an unfamiliar chemical.

Question 16Occupational Safety, Health and Working Environment

During a site inspection a plumber sees a trailing extension lead crossing a walkway used by other trades. What is the most appropriate immediate action?

  1. Cut the lead to remove the trip hazard
  2. Ignore it because the lead belongs to another trade
  3. Step over it carefully and continue working
  4. Reroute or cover the lead and report the hazard so it is controlled Correct answer.

Explanation

Trailing leads across walkways are a common trip hazard and can also be damaged, creating an electrical risk. The correct response is to remove or protect the hazard, for example by rerouting or using a cable ramp, and to report it so it is properly managed. Cutting a live lead is dangerous.

Question 17Occupational Safety, Health and Working Environment

A worker complains of dizziness and headache while working in a poorly ventilated basement where a petrol-powered pump is running. What is the most likely cause and correct response?

  1. Heat exhaustion; drink water and continue
  2. Carbon monoxide exposure; stop the engine, move to fresh air and seek medical help Correct answer.
  3. Dehydration; open a bottle of water
  4. Noise exposure; wear ear plugs and continue

Explanation

Petrol engines produce carbon monoxide, an odourless gas that causes headache, dizziness and can be fatal in enclosed spaces. The engine must be stopped and the affected person moved to fresh air with medical assessment. Continuing work in the space risks loss of consciousness.

Question 18Occupational Safety, Health and Working Environment

A plumber is preparing to weld a steel pipe support bracket in a room where the floor is covered with sawdust. Which control sequence is most appropriate?

  1. Open a window and weld without further preparation
  2. Clear or wet down combustibles, use a fire watch and keep an extinguisher ready Correct answer.
  3. Weld first and sweep up afterwards
  4. Cover the sawdust with a plastic sheet and weld

Explanation

Sawdust is highly combustible and can smoulder unnoticed after sparks land. The correct sequence is to remove or wet down the combustible material, assign a fire watch during and after the work, and keep suitable extinguishing equipment ready. A plastic cover can itself burn or trap heat.

Question 19Occupational Safety, Health and Working Environment

Two plumbers must install a pipe run at height on a scaffold. Which arrangement best meets fall-protection principles?

  1. Use a complete scaffold with guardrails and toe boards, and use a ladder or platform for access rather than climbing the frame Correct answer.
  2. Stand on the top guardrail to reach the fixing point
  3. Balance on a bucket placed on the platform
  4. Work without harness because the height is under three metres

Explanation

Fall protection relies on a properly constructed platform with guardrails and safe means of access, so workers never need to climb the frame or overreach. Standing on guardrails or improvised supports removes the very barrier meant to prevent falls. Even low heights can cause serious injury.

Question 20Occupational Safety, Health and Working Environment

A plumber is tasked with rodding a blocked drain that may connect to a sewer line where gases can build up. Which set of controls best reflects a safe system of work?

  1. Seal the manhole cover and work blind
  2. Assess and test the atmosphere, ventilate, use a standby person and wear appropriate PPE Correct answer.
  3. Use a higher-pressure jet without checking the drain direction
  4. Rod the drain alone at night to avoid disturbing others

Explanation

Sewer-connected drains can release toxic and flammable gases, so the safe system combines atmospheric assessment, ventilation, a standby person outside the space and suitable PPE. Working alone at night or sealing the cover removes the ability to detect and respond to gas. High-pressure jetting without checking direction can also injure the operator.

Question 21Trade Tools, Equipment and Materials

Which tool is specifically designed for cutting internal threads in a pipe fitting?

  1. Pipe wrench
  2. Reamer
  3. Die
  4. Tap Correct answer.

Explanation

A tap is a threaded cutting tool used to form internal threads inside a hole or fitting. A die cuts external threads on pipe, while a reamer only enlarges or smooths a hole. Confusing tap and die is a common error, so remember internal equals tap.

Question 22Trade Tools, Equipment and Materials

A plumber needs to measure the outside diameter of a 25 mm GI pipe accurately. Which instrument is most suitable?

  1. Steel rule
  2. Spirit level
  3. Try square
  4. Vernier caliper Correct answer.

Explanation

A vernier caliper measures external and internal diameters to a fraction of a millimetre using its main and vernier scales. A steel rule gives only coarse length readings and cannot grip a round profile reliably. The other tools check squareness or level and cannot measure diameter.

Question 23Trade Tools, Equipment and Materials

Which material is most commonly used for galvanized water supply pipes in domestic plumbing?

  1. Mild steel Correct answer.
  2. Copper
  3. Cast iron
  4. PVC

Explanation

Galvanizing is a zinc coating applied to mild steel to resist corrosion, so GI pipes are mild steel pipes coated with zinc. Copper, cast iron and PVC are separate materials that are not galvanized. The zinc layer protects the steel from rust in water supply lines.

Question 24Trade Tools, Equipment and Materials

Which hand tool is used to hold and turn pipes during assembly and dismantling?

  1. Chisel
  2. File
  3. Hacksaw
  4. Pipe wrench Correct answer.

Explanation

A pipe wrench has serrated jaws that grip round pipe and a long handle for leverage to turn it. A hacksaw cuts, a file smooths edges and a chisel cuts metal or masonry. Only the pipe wrench is designed to grip and rotate pipe.

Question 25Trade Tools, Equipment and Materials

What is the main purpose of applying solvent cement to PVC pipe joints?

  1. To insulate the pipe against heat loss
  2. To colour-code the pipeline
  3. To dissolve the surfaces and fuse them into a leak-proof joint Correct answer.
  4. To lubricate the joint for easy sliding

Explanation

Solvent cement softens the PVC surfaces so they fuse together as the solvent evaporates, creating a strong leak-proof joint. It is not a lubricant and does not provide thermal insulation or colour coding. Correct application with a primer ensures a sound bond.

Question 26Trade Tools, Equipment and Materials

Which PPE item protects a plumber's eyes while cutting or grinding metal pipe?

  1. Respirator
  2. Safety goggles Correct answer.
  3. Ear plugs
  4. Apron

Explanation

Safety goggles shield the eyes from flying metal chips, sparks and dust during cutting and grinding. Ear plugs protect hearing, a respirator protects the lungs and an apron protects the body, but none of these protects the eyes. Eye protection must be worn whenever cutting or grinding.

Question 27Trade Tools, Equipment and Materials

A plumber must cut a 50 mm GI pipe squarely by hand. Which sequence of tools gives the best result?

  1. Pipe wrench, then reamer
  2. Spanner, then sandpaper
  3. Hacksaw, then file the cut edge Correct answer.
  4. Chisel, then hammer the edge

Explanation

A hacksaw makes the cut and a half-round file removes burrs and squares the edge so threads can be cut cleanly. A chisel would deform the pipe, and wrenches or spanners cannot cut pipe. Filing after sawing is standard practice before threading.

Question 28Trade Tools, Equipment and Materials

Why is a pipe reamer used on the inside of a cut pipe before threading?

  1. To apply thread sealant
  2. To flatten the pipe end for a cap
  3. To remove the internal burr and prevent thread damage Correct answer.
  4. To enlarge the bore for higher flow

Explanation

Cutting pipe leaves a burr on the inner edge that can obstruct flow and interfere with threading and dies. Reaming removes this burr and restores a clean bore. A reamer does not enlarge the bore, flatten the end or apply sealant.

Question 29Trade Tools, Equipment and Materials

Which wrench is best suited for tightening the hexagonal nut of a compression fitting on a copper pipe?

  1. Stillson wrench
  2. Basin wrench
  3. Chain wrench
  4. Adjustable spanner Correct answer.

Explanation

An adjustable spanner grips the flat faces of hexagonal nuts without damaging them and suits compression fittings. A chain wrench or Stillson wrench has serrated jaws designed for round pipe and would damage the nut. A basin wrench is for reaching taps in awkward places.

Question 30Trade Tools, Equipment and Materials

A plumber is joining two copper pipes and needs a strong joint without a flame. Which method is most appropriate?

  1. Compression fitting Correct answer.
  2. Solvent welding
  3. Threading
  4. Lead caulking

Explanation

Compression fittings join copper pipe mechanically with a nut, olive and body, requiring no heat or flame. Solvent welding is for plastics, lead caulking is obsolete for copper and threading is used on steel pipe. Compression fittings are ideal where hot work is unsafe.

Question 31Trade Tools, Equipment and Materials

Which property makes stainless steel a preferred material for certain plumbing fittings?

  1. Corrosion resistance Correct answer.
  2. High magnetic strength
  3. Low melting point
  4. High electrical conductivity

Explanation

Stainless steel contains chromium, which forms a passive oxide layer that resists rust and corrosion in water systems. High conductivity, low melting point and magnetism are not the reasons it is chosen for plumbing fittings. Corrosion resistance ensures long service life and water quality.

Question 32Trade Tools, Equipment and Materials

What is the correct purpose of a pipe vice in a plumbing workshop?

  1. To test joints under pressure
  2. To bend pipe to a required angle
  3. To measure the length of pipe
  4. To hold pipe firmly while it is cut or threaded Correct answer.

Explanation

A pipe vice clamps the pipe securely so that cutting, reaming and threading can be done safely and accurately. Bending is done with a bender, measuring with tapes or rules, and pressure testing with a test pump. The vice provides grip only.

Question 33Trade Tools, Equipment and Materials

A plumber has to bend a 15 mm copper tube to a large radius without kinking. Which combination of tools is most suitable?

  1. Spring bender and bending machine Correct answer.
  2. Die and stock
  3. Hacksaw and file
  4. Reamer and vice

Explanation

A bending spring supports the tube wall from inside to prevent collapse, and a bending machine produces a smooth controlled radius. Hacksaws, dies and reamers are for cutting and threading, not bending. Supporting the bore is the key to avoiding kinks.

Question 34Trade Tools, Equipment and Materials

Which type of valve allows flow in only one direction and is used to prevent backflow in a supply line?

  1. Gate valve
  2. Globe valve
  3. Ball valve
  4. Check valve Correct answer.

Explanation

A check valve opens with forward flow and closes automatically when flow reverses, preventing backflow contamination. Gate, globe and ball valves are manually operated for isolation or regulation and do not stop reverse flow on their own. Check valves are therefore used as backflow preventers.

Question 35Trade Tools, Equipment and Materials

A plumber notices that a hacksaw blade keeps jumping out of the kerf while cutting thin-wall pipe. Which action most likely corrects the problem?

  1. Use a coarser blade with fewer teeth per inch
  2. Push harder on the saw
  3. Increase blade tension and use a finer-tooth blade Correct answer.
  4. Remove the blade guard

Explanation

Thin-wall pipe needs fine teeth so several teeth engage the wall and a properly tensioned blade so it tracks straight. A loose or coarse blade snags and jumps, and extra force worsens the problem. Correct tension and tooth pitch give a clean, straight cut.

Question 36Trade Tools, Equipment and Materials

Which sealant is appropriate for sealing the threaded joint of a hot water steel pipe?

  1. Wood putty
  2. Contact adhesive
  3. PTFE tape Correct answer.
  4. PVC solvent cement

Explanation

PTFE tape is chemically inert, withstands hot water and lubricates the threads so the joint seals tightly. PVC cement bonds plastic pipe only, and adhesives or putty are not rated for hot pressurised water. PTFE tape is the standard thread sealant for this service.

Question 37Trade Tools, Equipment and Materials

A plumber is selecting a material for buried drainage pipe carrying soil waste. Which material is most suitable?

  1. Aluminium sheet
  2. Galvanized mild steel
  3. PVC or cast iron Correct answer.
  4. Copper tube

Explanation

PVC and cast iron are the standard materials for soil and waste drainage because they resist corrosion and handle the required flows. Galvanized steel corrodes in soil, copper is costly and not usual for soil drains, and aluminium sheet is not a pipe material. Durability underground favours PVC or cast iron.

Question 38Trade Tools, Equipment and Materials

A plumber must identify an unknown pipe as GI or copper before jointing. Which simple field test gives the most reliable indication?

  1. Check colour and use a magnet Correct answer.
  2. Check the pipe length
  3. Check the pipe diameter
  4. Check the water pressure

Explanation

GI pipe is dull grey steel and is strongly attracted to a magnet, while copper is reddish and non-magnetic. Length, pressure and diameter do not identify material. Combining appearance with a magnet test reliably distinguishes the two in the field.

Question 39Trade Tools, Equipment and Materials

A plumber is threading a 40 mm steel pipe and the die is hard to turn and produces torn threads. Which cause is most likely?

  1. The pipe is too short
  2. The vice is too tight
  3. The pipe end is not chamfered and the die lacks lubrication Correct answer.
  4. The die is too sharp and new

Explanation

A pipe end must be chamfered or tapered so the die starts cleanly, and cutting oil must lubricate the cut to prevent torn threads and overheating. A short pipe or a tight vice does not cause torn threads, and a sharp die cuts better. Chamfering and lubrication are the standard remedies.

Question 40Trade Tools, Equipment and Materials

A plumber finds that a compression joint on a copper pipe weeps at the nut even after tightening. Which analysis is most reasonable before adding more force?

  1. The water pressure is too low
  2. The pipe diameter is too small
  3. The nut is made of brass
  4. The olive is misaligned or the pipe end is not square and clean Correct answer.

Explanation

Compression joints seal when a square, clean pipe end seats correctly in a well-aligned olive inside the fitting. A skewed olive or burred, out-of-square end prevents sealing, and over-tightening may crush the olive. Diameter, low pressure and brass material are not the cause.

Question 41Plumbing Works and Pipe Fitting

Which material is most commonly specified for buried cold-water service lines in Indian domestic plumbing because of its corrosion resistance and long service life?

  1. Cast iron soil pipe
  2. Rigid PVC pipe Correct answer.
  3. Galvanised iron pipe
  4. Copper tube

Explanation

Rigid PVC is widely used for buried cold-water service lines in Indian domestic work because it resists corrosion, resists scale build-up and gives a long, low-maintenance service life at low cost. Galvanised iron corrodes internally over time, cast iron is a drainage material, and copper is rarely used underground in ordinary domestic work because of cost.

Question 42Plumbing Works and Pipe Fitting

A plumber needs to join two PVC water supply pipes permanently in a concealed wall chase. Which jointing method is correct for this material?

  1. Threaded socket with hemp and white lead
  2. Solvent cement welding with a socket fitting Correct answer.
  3. Compression ferrule with rubber olive
  4. Lead-caulked bell and spigot joint

Explanation

PVC is joined by solvent cementing: the pipe end and the socket are cleaned, primed and coated with cement, then pushed together so the softened surfaces fuse into a continuous joint. Threading, caulking and compression ferrules belong to metal systems and are not used for plain PVC pressure pipe.

Question 43Plumbing Works and Pipe Fitting

In a house drainage system, what is the main purpose of the vent pipe connected to the soil stack?

  1. To drain surplus rainwater from the roof
  2. To equalise air pressure in the stack and protect trap seals Correct answer.
  3. To carry kitchen waste to the gully
  4. To supply fresh water to the cistern

Explanation

A vent pipe admits and releases air so that pressure changes in the stack during discharge do not siphon the water seal out of fixture traps. Keeping the trap seal intact is what prevents foul air and sewer gas from entering the building.

Question 44Plumbing Works and Pipe Fitting

Which tool is used to cut an internal thread inside a socket fitting in GI pipe work?

  1. Die stock with dies
  2. Reamer
  3. Taps Correct answer.
  4. Pipe cutter wheel

Explanation

Taps cut internal (female) threads inside sockets and fittings, while dies cut external threads on the pipe end. A pipe cutter simply severs the pipe and a reamer removes the internal burr left by cutting.

Question 45Plumbing Works and Pipe Fitting

A water closet is installed in a bathroom and the finished floor level is fixed. What is the standard practice for setting the height of the WC pan outlet connection to the soil pipe?

  1. Set the outlet so the pan sits level with its base on the finished floor and the connector has a slight fall to the stack Correct answer.
  2. Raise the pan on a mortar plinth so the outlet slopes uphill to the stack
  3. Seal the outlet directly to the stack with no connector and no fall
  4. Connect the outlet horizontally so waste stands in the pipe

Explanation

The pan must rest level on its base on the finished floor, and the outlet connector must fall slightly towards the stack so waste drains away by gravity. An uphill or level outlet allows solids and water to stand in the connector, causing blockages and odour.

Question 46Plumbing Works and Pipe Fitting

What is the correct sequence when making a threaded GI pipe joint using a socket?

  1. Insert a rubber ring in the socket and push the pipe home
  2. Cut thread, apply jointing compound on the thread, screw into the socket, and tighten with a pipe wrench Correct answer.
  3. Heat the socket, force the pipe in, and cool with water
  4. Apply cement, push the pipe in, and wipe the surplus

Explanation

For a threaded GI joint the pipe end is threaded, the thread is cleaned and coated with jointing compound or PTFE tape, and the pipe is screwed into the socket and tightened with a pipe wrench. The compound fills the spiral gap between the threads to make the joint leak-proof.

Question 47Plumbing Works and Pipe Fitting

Which of the following is the correct working pressure test for a newly installed concealed cold-water pipe line before closing the chase?

  1. Fill with water, apply the specified test pressure with a hand pump, and hold it for the required period with no drop Correct answer.
  2. Blow compressed air through the line and listen for leaks
  3. Pour a bucket of water through the line and check for drips at the tap
  4. Run the tap for five minutes and observe the flow

Explanation

A pressure test fills the line with water, raises it to the specified test pressure with a hand pump and holds it for the required period; a steady gauge reading with no visible leakage proves the joints are sound. This must be done before the chase is closed so any defect can be repaired.

Question 48Plumbing Works and Pipe Fitting

What is the primary function of a P-trap fitted below a wash basin?

  1. To reduce the noise of discharging water
  2. To retain a water seal that blocks sewer gas from entering the room Correct answer.
  3. To increase the water flow rate to the drain
  4. To filter hair and soap from the waste

Explanation

The dip of the P-trap holds a measured depth of water that forms a barrier against foul air and gases travelling back from the drainage system. The trap does not filter, boost flow or act as a silencer.

Question 49Plumbing Works and Pipe Fitting

A GI cold-water distribution pipe passes through a brick wall. Which provision best protects the pipe against corrosion and abrasion at the penetration?

  1. Weld the pipe rigidly to the wall reinforcement
  2. Coat the pipe with whitewash before embedding
  3. Bury the pipe directly in the brickwork with no clearance
  4. Wrap the pipe with a sleeve and seal the annular gap with mortar or mastic Correct answer.

Explanation

A sleeve gives a clearance around the pipe so that wall movement and moisture do not abrade or corrode the pipe surface, and sealing the annular gap keeps out water, dust and insects. Rigid embedding or direct contact with brickwork damages the protective coating over time.

Question 50Plumbing Works and Pipe Fitting

While threading a 25 mm GI pipe, the die produces a ragged, torn thread. Which cause is most likely?

  1. The socket is of the wrong size
  2. The pipe vice was tightened too firmly
  3. The die is worn or the pipe was not properly reamed and lubricated Correct answer.
  4. The pipe was cut with a hacksaw instead of a cutter

Explanation

Ragged threads usually result from a blunt or wrongly adjusted die, or from cutting dry on an unreamed pipe end where the burr and scale tear the thread. Correct die setting, reaming and cutting oil give a clean, full-depth thread.