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Punjab PSEB Matric NSQF Plumbing (Assistant Plumber) study materials
Punjab PSEB Matric NSQF Plumbing (Assistant Plumber) study resources

Punjab PSEB Matric NSQF Plumbing (Assistant Plumber) practice questions

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Question 1Plumbing tools, equipment and safe handling

For general pipe work on a site, which PPE combination is the minimum expected before you start cutting GI pipe with a hacksaw?

  1. Ear plugs, face shield and rubber boots
  2. Helmet, welding goggles and leather gauntlets
  3. Cotton cap, apron and sandals
  4. Safety goggles, hand gloves and safety shoes Correct answer.

Explanation

Cutting metal pipe produces flying chips and sharp burrs, so eye protection, hand protection and closed safety footwear are the basic minimum on any plumbing site. Other items such as helmets or ear protection are added only when the specific task demands them.

Question 2Plumbing tools, equipment and safe handling

A pipe wrench is being used to tighten a 25 mm GI union. Which practice keeps the tool and the fitting in good condition?

  1. Strike the wrench handle with a hammer to seat the jaws
  2. Pull the handle towards you so the jaw teeth bite into the pipe
  3. Apply the load with a pipe extension on the handle for extra force
  4. Fit the wrench so the jaws grip the fitting squarely and pull the handle Correct answer.

Explanation

A pipe wrench is designed so that pulling the handle closes the jaws onto the work; the jaws must sit square on the fitting to avoid slipping and rounding the flats. Extensions and hammer blows overload the handle and the adjusting nut.

Question 3Plumbing tools, equipment and safe handling

Which tool is the correct choice for cutting an internal thread on a 20 mm GI pipe on site?

  1. Die stock with a die head Correct answer.
  2. Pipe cutter with a cutting wheel
  3. Chain pipe vice
  4. Flat file with a safe edge

Explanation

External threads on pipe are cut with a die held in a die stock, which is turned onto the pipe end after it is chamfered. A pipe cutter only severs the pipe, and a vice only holds it.

Question 4Plumbing tools, equipment and safe handling

Before using a hand hacksaw to cut a 50 mm CI pipe, what is the correct way to set the blade?

  1. Fit the blade with the teeth facing sideways to clear chips
  2. Fit the blade loosely so it can flex in the cut
  3. Fit the blade with teeth pointing towards the handle
  4. Fit the blade with teeth pointing forward, away from the handle, and tension it firmly Correct answer.

Explanation

A hacksaw blade cuts on the forward stroke, so the teeth must point away from the handle and the blade must be tensioned so it runs straight. A loose or reversed blade wanders in the cut and breaks easily.

Question 5Plumbing tools, equipment and safe handling

A plumber must hold a 100 mm diameter GI pipe firmly while threading it. Which support is appropriate?

  1. Two bricks stacked under the pipe
  2. A bench vice gripping the pipe by its threaded end
  3. A wooden bench with the pipe held by hand
  4. A chain pipe vice or a pipe vice fixed to a sturdy stand Correct answer.

Explanation

Threading applies high torque, so the pipe must be gripped in a proper pipe vice or chain vice that spreads the clamping load and leaves both hands free to turn the die stock. Improvised supports slip and can injure the user.

Question 6Plumbing tools, equipment and safe handling

Why is a pipe cutter preferred over a hacksaw when cutting copper tube for a concealed installation?

  1. It produces a square cut with minimal burr, giving a cleaner joint Correct answer.
  2. It can cut bends and fittings as well as straight tube
  3. It cuts faster through hardened steel
  4. It eliminates the need to ream the tube

Explanation

A wheel-type pipe cutter rolls a square, burr-free cut that seats well in fittings and solders cleanly, which matters for concealed work. A hacksaw cut is rarely square and leaves a burr that must be filed off.

Question 7Plumbing tools, equipment and safe handling

A gas cylinder for brazing is being stored in the workshop. Which arrangement follows safe handling practice?

  1. Cylinders stored next to the paint store to keep them dry
  2. Cylinders lying flat under the workbench with the regulator left on
  3. Cylinders chained to a trolley with the hoses left pressurised
  4. Cylinders upright, secured against falling, with valve caps on and away from heat Correct answer.

Explanation

Compressed gas cylinders must stand upright and be restrained so they cannot fall, with protective caps fitted when not in use, and kept away from heat and ignition sources. Regulators and hoses should be removed and the valves closed.

Question 8Plumbing tools, equipment and safe handling

Which item of PPE is essential when you are soldering copper joints with a blowlamp in a confined toilet?

  1. A leather apron
  2. Non-conductive rubber matting
  3. Flame-retardant gloves and eye protection, plus adequate ventilation Correct answer.
  4. A dust mask rated for fine particles

Explanation

Blowlamp work produces a hot flame, sparks and flux fumes, so gloves, eye protection and ventilation are the essentials in a small room. A dust mask does not stop flux fumes and an apron alone leaves eyes and hands exposed.

Question 9Plumbing tools, equipment and safe handling

Which tool is designed specifically for bending a 15 mm copper tube by hand without kinking it?

  1. Spirit level
  2. Stillson wrench
  3. Tube reamer
  4. Spring bender inserted into the tube Correct answer.

Explanation

A bending spring is pushed inside the tube (or slipped over it) to support the wall so the tube bends smoothly without collapsing. The spring is then withdrawn by twisting it out.

Question 10Plumbing tools, equipment and safe handling

A plumber needs to check the fall of a 100 mm soil pipe over a 6 m run. Which tool gives the most reliable result?

  1. A plumb bob
  2. A steel measuring tape held horizontally
  3. A try square
  4. A spirit level with a graduated fall attachment or a laser level Correct answer.

Explanation

Fall is a small gradient over a long run, so it is set with a spirit level fitted with a fall gauge or with a laser level, then measured against the pipe. A tape or plumb bob cannot show a gradient of a few millimetres per metre.

Question 11Plumbing tools, equipment and safe handling

What is the purpose of a pipe reamer after cutting GI pipe with a wheel cutter?

  1. To cut the external thread on the pipe
  2. To straighten a bent length of pipe
  3. To enlarge the pipe bore to the next size
  4. To remove the internal burr so flow is not restricted and threads form cleanly Correct answer.

Explanation

A wheel cutter leaves a raised internal burr that reduces the bore and disturbs flow; the reamer removes it and also helps chamfer the end before threading. It does not change the pipe size.

Question 12Plumbing tools, equipment and safe handling

A hacksaw blade marked 18 TPI is chosen for a job. For which material is this blade most suitable?

  1. Stainless steel sheet of 0.8 mm
  2. Thin-wall copper tube of 1 mm wall
  3. Thick-walled cast iron pipe and solid bar Correct answer.
  4. PVC conduit of 2 mm wall

Explanation

Coarse teeth (about 18 TPI) give the clearance needed for thick sections such as cast iron pipe and solid bar. Thin walls need fine teeth (24 to 32 TPI) so that at least two or three teeth stay in contact with the work.

Question 13Plumbing tools, equipment and safe handling

A plumber is chiselling a chase in a brick wall for a concealed pipe. Which combination of controls is most appropriate?

  1. Goggles, dust mask, gloves and hearing protection, with the area screened off Correct answer.
  2. No PPE, provided the work is done quickly
  3. Goggles only, because the chisel is hand held
  4. Dust mask only, because the main hazard is dust

Explanation

Chiselling brick creates flying chips, silica dust and impact noise, so eye, respiratory, hand and hearing protection are all justified, and screening protects others nearby. Hand tools still generate enough dust and noise to require controls.

Question 14Plumbing tools, equipment and safe handling

Which statement about the safe use of an electric pipe-threading machine is correct?

  1. Gloves should be worn loosely so they can be pulled off quickly
  2. The die head may be adjusted while the machine is running
  3. The pipe must be securely clamped and the machine guarded before starting Correct answer.
  4. Loose clothing is acceptable if the operator stands to one side

Explanation

Rotating machinery can draw in clothing and hands, so the pipe must be clamped, guards kept in place and adjustments made only with the machine stopped. Loose gloves and sleeves are a serious entanglement risk.

Question 15Plumbing tools, equipment and safe handling

A caulking tool and a yarning iron are used in which plumbing operation?

  1. Joining copper tube by soldering
  2. Cutting threads on GI pipe
  3. Lead-wiping and caulked joints on cast iron soil pipe Correct answer.
  4. Testing a drain for air tightness

Explanation

Yarning irons pack the jointing material into the socket and caulking tools tamp it down in lead and caulked cast iron joints. They are traditional jointing tools, not cutting or testing tools.

Question 16Plumbing tools, equipment and safe handling

Which action is correct before using a spirit level that has been dropped on site?

  1. Use it as it is, since the bubble always settles in the middle
  2. Shake it to free the bubble
  3. Fill the vial with water to make the bubble clearer
  4. Check it against a known level surface, then reverse it end for end to confirm the bubble repeats Correct answer.

Explanation

A dropped level may have a shifted vial, so it must be checked by reversing it on the same surface: if the bubble reads the same both ways, the vial is true. Never open or fill a vial.

Question 17Plumbing tools, equipment and safe handling

When using a hand-held power drill to fix pipe clips to a brick wall, which practice reduces the risk of injury?

  1. Use a blunt bit with extra pressure to speed up drilling
  2. Stand on a bucket to reach high clips
  3. Wear eye protection, keep the drill bit sharp and let the drill do the work Correct answer.
  4. Hold the drill with one hand and steady the bit with the other

Explanation

Sharp bits, moderate feed pressure and eye protection keep the drill under control and reduce the chance of the bit snatching or breaking. Never guide a rotating bit with the hand or work from an unstable support.

Question 18Plumbing tools, equipment and safe handling

Which tool would you select to cut an access opening in a plasterboard ceiling for a concealed pipe without damaging surrounding board?

  1. Pipe cutter
  2. Stillson wrench
  3. Pad saw or plasterboard saw Correct answer.
  4. Bolt cutter

Explanation

A pad saw or plasterboard saw has a narrow blade that can be plunged into the board and steered to cut a controlled opening. Bolt cutters, wrenches and pipe cutters are for metal work and would cause damage.

Question 19Plumbing tools, equipment and safe handling

A plumber needs to remove a rounded, corroded nut on a tap connector. Which tool gives the best chance of success?

  1. A hacksaw applied to the nut
  2. A pipe wrench applied to the pipe body
  3. A six-point socket or a locking plier designed for rounded nuts Correct answer.
  4. An adjustable wrench with worn jaws

Explanation

A six-point socket or a locking plier with hardened jaws grips all the flats and bites into a rounded nut. Worn adjustable jaws slip, and cutting the nut risks damaging the fitting and the pipe.

Question 20Plumbing tools, equipment and safe handling

What is the correct way to store a hacksaw and other edged tools at the end of a shift?

  1. Oil them and leave them on the scaffold
  2. Hang them by the blade on a nail
  3. Clean them, fit blade guards or sheaths and return them to the tool box Correct answer.
  4. Leave them on the floor near the work area

Explanation

Edged tools should be cleaned, guarded and stored in a designated place so the teeth are protected and nobody is cut when reaching for them. Leaving tools on the floor or scaffold creates both damage and trip hazards.

Question 21Plumbing tools, equipment and safe handling

A plumber must lift a 3 m length of 100 mm cast iron pipe onto a pipe stand. Which handling method is correct?

  1. Drag it along the floor to the stand
  2. Use two persons or a lifting aid, keep the back straight and bend the knees Correct answer.
  3. Lift it alone with the back bent and twist to place it
  4. Roll it up a plank onto the stand

Explanation

Cast iron pipe of this size is heavy and awkward, so a team lift or mechanical aid is needed with good lifting posture to protect the spine. Dragging damages the pipe and the floor, and rolling up a plank is uncontrolled.

Question 22Plumbing tools, equipment and safe handling

Which statement correctly describes the use of a crow's foot or basin wrench when tightening a tap backnut under a basin?

  1. It measures the torque applied to the nut
  2. It reaches into the confined space and grips the nut from below Correct answer.
  3. It is a type of pipe cutter for small copper tube
  4. It is used to cut the supply pipe to length

Explanation

A basin wrench has a long shank and a pivoting jaw so the nut can be reached and turned from below in the narrow space behind the basin. It is a gripping tool, not a cutting or measuring tool.

Question 23Plumbing tools, equipment and safe handling

A site store holds both a pipe vice and a bench vice. For holding a 40 mm GI pipe to cut a thread, why is the pipe vice the better choice?

  1. It has larger, serrated jaws shaped to grip round pipe without crushing it Correct answer.
  2. It has a built-in die for cutting threads
  3. It can be used to bend the pipe as well
  4. It is lighter and can be carried in a tool bag

Explanation

A pipe vice is built with wide, shaped jaws that hold round sections securely against rotation without crushing the wall, which is exactly what threading demands. A bench vice is designed for flat work and smaller clamping loads.

Question 24Plumbing tools, equipment and safe handling

What is the main reason for wearing hearing protection when using a disc cutter on cast iron pipe?

  1. To improve concentration on the cut line
  2. To protect against sparks entering the ear canal
  3. To reduce exposure to high noise levels that can cause permanent hearing loss Correct answer.
  4. To keep dust out of the ears

Explanation

A disc cutter produces noise well above the level at which hearing protection is required, and prolonged exposure causes irreversible hearing loss. Dust and sparks are controlled by eye and respiratory protection, not by ear defenders.

Question 25Pipes, fittings, joints and plumbing materials

Which material is most commonly used for the water supply service pipe laid underground from the street main to a building in modern Indian plumbing practice?

  1. Rigid PVC pipe
  2. Unplasticised PVC (uPVC) or HDPE pipe Correct answer.
  3. Galvanised mild steel pipe
  4. Cast iron soil pipe

Explanation

uPVC and HDPE are the standard materials for underground service connections because they resist corrosion, have smooth bores and are easily jointed. They are approved for potable water supply lines and handle soil loads well. Galvanised steel tends to corrode, and cast iron is reserved for drainage rather than pressure supply.

Question 26Pipes, fittings, joints and plumbing materials

A plumber needs to join two lengths of 15 mm copper tube for a hot water line inside a wall. Which jointing method gives a permanent, pressure-tight joint suitable for concealed work?

  1. Compression fitting with brass olives
  2. Threaded coupling with hemp
  3. Push-fit plastic fitting
  4. Lead-free solder capillary joint Correct answer.

Explanation

A soldered capillary joint fuses the fitting and tube into a single metallic bond, making it permanent and suitable for concealment. Compression fittings rely on mechanical seals that can loosen and are generally avoided in inaccessible locations. Push-fit and threaded joints are not appropriate for copper hot water lines in walls.

Question 27Pipes, fittings, joints and plumbing materials

What does the nominal bore (NB) designation of a pipe indicate?

  1. The maximum working pressure in bar
  2. The wall thickness in millimetres
  3. The exact outside diameter in millimetres
  4. A nominal size used for reference, not the exact bore or outside diameter Correct answer.

Explanation

Nominal bore is a reference size that groups pipes of a given approximate internal diameter; the actual bore and outside diameter vary with schedule and standard. It is not a precise dimension and does not indicate pressure rating. Plumbers must consult the relevant standard table for actual dimensions.

Question 28Pipes, fittings, joints and plumbing materials

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

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

Explanation

A reducer is specifically designed to join a larger pipe to a smaller one in line. Elbows change direction, tees create a branch, and unions allow future disconnection. Only the reducer performs the diameter change function.

Question 29Pipes, fittings, joints and plumbing materials

In a soil and waste system, why are trap seals required at each fixture?

  1. To filter solid waste before it enters the drain
  2. To increase water pressure at the fixture
  3. To reduce the noise of flowing water
  4. To prevent sewer gases from entering the building Correct answer.

Explanation

The water seal in a trap blocks the passage of foul air and gases from the drainage system into occupied spaces. Without a seal, sewer gas could enter the building and create health and odour problems. Traps do not filter waste or affect supply pressure.

Question 30Pipes, fittings, joints and plumbing materials

A plumber is installing a CI (cast iron) soil stack and needs a joint that allows slight movement due to thermal expansion. Which joint type is traditionally used?

  1. Compression ring joint
  2. Solvent cement joint
  3. Lead-caulked socket joint Correct answer.
  4. Rigid welded joint

Explanation

Traditional cast iron soil pipe uses socket and spigot joints with lead caulking or modern elastomeric gaskets, which accommodate slight movement. Welding and solvent cement are not applicable to cast iron soil pipe. Compression ring joints are used for copper and plastic, not CI soil pipe.

Question 31Pipes, fittings, joints and plumbing materials

Which plastic material is most suitable for hot water distribution lines up to about 80 degrees Celsius?

  1. CPVC Correct answer.
  2. PVC sewer pipe
  3. HDPE
  4. uPVC

Explanation

Chlorinated polyvinyl chloride (CPVC) has a higher temperature rating than standard uPVC and is approved for hot water distribution. uPVC softens at higher temperatures, while HDPE is normally used for cold water and sewerage. PVC sewer pipe is not rated for potable hot water.

Question 32Pipes, fittings, joints and plumbing materials

What is the primary function of a P-trap in a wash basin waste connection?

  1. To prevent backflow of potable water
  2. To store water as a seal against foul gases Correct answer.
  3. To increase the flow velocity of waste water
  4. To support the basin from below

Explanation

The P-trap retains a water seal that prevents sewer gases from rising into the fixture and room. It is a drainage component and does not affect supply backflow or structural support. Flow velocity is not increased by the trap.

Question 33Pipes, fittings, joints and plumbing materials

Which type of valve is best suited for isolating a section of a domestic water supply line, allowing quick shut-off with a quarter turn?

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

Explanation

A ball valve uses a rotating drilled sphere to give quick quarter-turn isolation with minimal pressure loss when open. Gate valves require multiple turns and globe valves are used for throttling. Check valves allow flow in one direction only and cannot isolate manually.

Question 34Pipes, fittings, joints and plumbing materials

When solvent-cementing two PVC pipes, what is the correct sequence of operations?

  1. Apply cement, then primer, then push together
  2. Clean, apply primer, apply cement, then push and twist together Correct answer.
  3. Apply primer only, then push together
  4. Heat the pipe ends, then push together

Explanation

PVC solvent welding requires cleaning the surfaces, applying primer to soften the plastic, then applying cement and assembling with a slight twist to spread the cement evenly. This produces a fused, leak-free joint. Primer alone or heat fusion is not the correct method for PVC solvent joints.

Question 35Pipes, fittings, joints and plumbing materials

What is the main advantage of using a compression fitting on copper tube in a visible location?

  1. It is stronger than a soldered joint
  2. It is suitable for gas lines at high pressure
  3. It requires no tightening
  4. It can be dismantled and remade without cutting the tube Correct answer.

Explanation

Compression fittings use a nut and olive to grip the tube, allowing the joint to be loosened and remade for maintenance without cutting. They are not stronger than soldered joints and are not the preferred choice for high-pressure gas. They must be tightened properly to seal.

Question 36Pipes, fittings, joints and plumbing materials

Which pipe material is preferred for underground drainage because of its resistance to chemicals and smooth internal bore, and is commonly joined with rubber ring push-fit joints?

  1. Copper
  2. Asbestos cement
  3. Galvanised steel
  4. uPVC Correct answer.

Explanation

uPVC drainage pipe is widely used underground because it resists many chemicals, has a smooth bore for good flow, and uses elastomeric ring push-fit joints for speed. Steel and copper corrode in soil, and asbestos cement is no longer acceptable due to health hazards.

Question 37Pipes, fittings, joints and plumbing materials

A plumber observes that a water closet pan is connected to the soil pipe with a pan connector that has a flexible rubber sleeve. What is the main purpose of this connector?

  1. To allow slight misalignment between the pan outlet and the soil pipe Correct answer.
  2. To increase the flush volume
  3. To prevent water hammer
  4. To filter solid waste

Explanation

Flexible pan connectors accommodate small offsets and misalignments between the WC outlet and the soil pipe, simplifying installation. They do not change flush volume, prevent water hammer, or filter waste. Their role is purely to make a secure, slightly flexible connection.

Question 38Pipes, fittings, joints and plumbing materials

Which of the following is a characteristic of a gate valve compared with a globe valve in a water supply line?

  1. Globe valve offers lower resistance to flow when fully open
  2. Globe valve cannot be used for water
  3. Gate valve is designed mainly for throttling
  4. Gate valve offers lower resistance to flow when fully open Correct answer.

Explanation

A gate valve has a straight-through passage when fully open, so it causes very little pressure loss. Globe valves have a more tortuous path and are better for throttling but create higher resistance. Gate valves are not intended for throttling.

Question 39Pipes, fittings, joints and plumbing materials

What does the term 'schedule' refer to in steel pipe specification?

  1. The type of thread on the ends
  2. The colour code of the pipe
  3. The wall thickness classification Correct answer.
  4. The length of each pipe section

Explanation

In steel pipe standards, schedule (such as Sch 40 or Sch 80) denotes wall thickness, which determines pressure rating for a given nominal size. It is not a colour code, length, or thread type. Thicker schedules carry higher pressure.

Question 40Pipes, fittings, joints and plumbing materials

A plumber needs to connect a copper tube to a galvanised steel pipe. Which precaution is most important to prevent corrosion?

  1. Use a rubber hose between them
  2. Use a dielectric union to separate the dissimilar metals Correct answer.
  3. Solder the copper directly to the steel
  4. Apply more thread tape

Explanation

Dissimilar metals in contact with an electrolyte create galvanic corrosion; a dielectric union breaks the electrical path between copper and steel. Direct soldering of copper to steel is impractical and worsens corrosion. Rubber hose is not a pressure-rated permanent solution, and thread tape does not stop galvanic action.

Question 41Pipes, fittings, joints and plumbing materials

Which type of fitting would you use to change the direction of a pipeline by 90 degrees?

  1. Coupling
  2. Bend or elbow Correct answer.
  3. Reducer
  4. Cap

Explanation

A bend or elbow is designed to turn the pipeline through a specified angle such as 90 degrees. Couplings join straight lengths, reducers change diameter, and caps close off a pipe end. Only the elbow or bend changes direction.

Question 42Pipes, fittings, joints and plumbing materials

Why is a vent pipe (soil vent) provided in a drainage system?

  1. To allow air into the system and protect trap seals from siphonage Correct answer.
  2. To increase the flow of sewage
  3. To supply water to the fixtures
  4. To drain rainwater from the roof

Explanation

The vent pipe admits air into the drainage system so that pressure changes during flow do not siphon water out of trap seals. It also helps foul air escape above roof level. It does not supply water, drain rainwater, or increase sewage flow.

Question 43Pipes, fittings, joints and plumbing materials

Which jointing method is used for HDPE pipes in underground water mains where a strong, leak-free, monolithic joint is required?

  1. Lead caulked joint
  2. Solvent cement joint
  3. Threaded joint
  4. Butt fusion welding Correct answer.

Explanation

HDPE is joined by heat fusion, including butt fusion, which melts the pipe ends and fuses them into a continuous joint as strong as the pipe. HDPE cannot be solvent-cemented, and threading or lead caulking is not applicable. Butt fusion is standard for buried HDPE mains.

Question 44Pipes, fittings, joints and plumbing materials

What is the purpose of a check valve in a plumbing system?

  1. To allow flow in one direction only Correct answer.
  2. To regulate the temperature of water
  3. To filter suspended particles
  4. To reduce the pressure of water

Explanation

A check valve permits flow in one direction and prevents reverse flow, protecting against backflow and protecting pumps. It does not regulate temperature, reduce pressure by design, or filter particles. Its function is directional control.

Question 45Pipes, fittings, joints and plumbing materials

A plumber is choosing between a cast iron and a PVC soil pipe for an internal stack. Which statement is correct?

  1. PVC is quieter than cast iron
  2. PVC requires lead caulking
  3. Cast iron is quieter in operation but heavier and costlier to install Correct answer.
  4. Cast iron cannot be used for soil stacks

Explanation

Cast iron soil pipe has greater mass and therefore reduces noise from flowing waste, but it is heavy, costly, and needs careful support. PVC is lighter and cheaper but noisier. Cast iron is a traditional soil stack material, and PVC uses solvent or ring joints, not lead caulking.

Question 46Pipes, fittings, joints and plumbing materials

Which of the following best describes a 'boss white' or jointing compound used in plumbing?

  1. A type of plastic pipe
  2. A tool for bending pipes
  3. A paste applied to threaded joints to help seal them Correct answer.
  4. A soldering flux for copper

Explanation

Boss white is a traditional jointing paste applied to threaded pipe joints, often with hemp, to help create a seal. It is not a pipe material, flux, or tool. Modern alternatives include PTFE tape and anaerobic sealants.

Question 47Pipes, fittings, joints and plumbing materials

What is the main reason for using PTFE tape on threaded pipe joints?

  1. To join pipes of different diameters
  2. To increase the strength of the pipe
  3. To lubricate the threads and fill the spiral gap to prevent leaks Correct answer.
  4. To prevent galvanic corrosion

Explanation

PTFE tape lubricates the threads so the joint tightens fully and fills the spiral clearance between male and female threads to stop leaks. It does not strengthen the pipe, stop galvanic corrosion, or change diameters. It is a thread sealant, not a structural component.

Question 48Pipes, fittings, joints and plumbing materials

Which statement about the pressure rating of a pipe is correct?

  1. It is the same for all pipes of a given nominal bore
  2. It depends on material, wall thickness, and temperature Correct answer.
  3. It decreases as wall thickness increases
  4. It is determined only by the pipe length

Explanation

Pressure rating is a function of the pipe material's strength, the wall thickness, and the operating temperature, since strength falls as temperature rises. Nominal bore alone does not fix the rating, and longer pipes do not have lower ratings. Thicker walls increase, not decrease, pressure capacity.

Question 49Pipes, fittings, joints and plumbing materials

A plumber is installing a water supply line and needs to make a branch connection to supply a wash basin while continuing the main run. Which fitting is appropriate?

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

Explanation

A tee has three openings and allows a branch to be taken off a straight run while the main line continues. Elbows change direction, reducers change diameter, and unions allow disconnection. The tee is the correct branch fitting.

Question 50Pipes, fittings, joints and plumbing materials

Which material is used to make a socket-and-spigot joint on a cast iron soil pipe flexible enough to absorb small ground movement?

  1. A coating of solvent cement applied to the spigot
  2. Molten lead run into the hub over a gasket
  3. A rubber ring gasket compressed inside the hub Correct answer.
  4. Lead wool packed over a dry cement base

Explanation

Modern cast iron soil pipes use push-fit rubber ring gaskets seated in the hub; the spigot slides in and compresses the ring, giving a watertight joint that tolerates slight movement and thermal expansion. Traditional methods used lead or cement, but these are rigid and do not absorb movement.