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Punjab PSEB Sr. Sec. NSQF Plumbing (Advanced Plumbing Technician) study materials
Punjab PSEB Sr. Sec. NSQF Plumbing (Advanced Plumbing Technician) study resources

Punjab PSEB Sr. Sec. NSQF Plumbing (Advanced Plumbing Technician) practice questions

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Question 1Occupational Health, Safety and Workplace Practices

A technician is about to cut a 100 mm cast-iron soil pipe with an abrasive cut-off saw on a site where other trades are working nearby. Which personal protective equipment is required for this cut?

  1. Safety goggles alone, since the wheel guard contains the sparks
  2. Ear defenders alone, since the guard stops the particles
  3. Face shield over spectacles plus hearing protection Correct answer.
  4. A dust mask and cotton gloves, since the main risk is fine dust

Explanation

An abrasive cut-off saw throws hot abrasive particles, metal fragments and sparks well beyond the guard and produces noise levels that commonly exceed 85 dB(A). Impact-rated eye protection worn under a full face shield protects the eyes and the whole face, and hearing protection prevents noise-induced hearing loss. A wheel guard is a machine control, not personal protection, so it never removes the need for either item.

Question 2Occupational Health, Safety and Workplace Practices

Two technicians must move a 3 m length of 150 mm cast-iron pipe from a rack to a trench edge about 15 m away. Which handling method is safest?

  1. Drag the pipe along the ground with a rope to avoid any lifting
  2. Use a pipe trolley or carry it at waist height with two people Correct answer.
  3. Roll the pipe over the trench edge and let it drop to the bottom
  4. Each technician lifts one end and carries it at shoulder height

Explanation

Cast iron is dense, so a 3 m length is far heavier than it looks and shoulder-height carrying raises the load moment on the spine while blocking the view of the route. Mechanical aids such as a pipe trolley are preferred, and where manual lifting is unavoidable the load should be shared, kept close to the body at about waist height, and the route planned. Dragging damages the protective coating, and dropping the pipe into a trench endangers anyone working below.

Question 3Occupational Health, Safety and Workplace Practices

A technician needs to reach a ceiling void to run a short pipe run and will use a leaning ladder to get there. Which ladder set-up is correct?

  1. Set it at about 75 degrees and tie the stiles to the wall Correct answer.
  2. Stand it on loose spoil so the feet can bed into the ground
  3. Set it at 45 degrees so the rungs are easier to climb under the void
  4. Set it almost vertical against the wall so it cannot slip outwards

Explanation

The safe leaning angle is roughly 75 degrees, which corresponds to one unit out from the wall for every four units of height, and the ladder must be secured at the top so it cannot slip or be pushed sideways. Feet must rest on firm, level ground, and the ladder should extend about one metre above the landing point. Near-vertical and 45-degree set-ups both allow the ladder to slide or tip.

Question 4Occupational Health, Safety and Workplace Practices

A technician is to replace the element in an electric immersion heater that is hard-wired to its own circuit. What is the correct isolation procedure before the cover is removed?

  1. Isolate at the breaker, lock and tag it, and prove the circuit dead Correct answer.
  2. Switch off at the wall-mounted thermostat and begin work at once
  3. Ask a colleague to stand at the consumer unit and warn if it is switched on
  4. Turn the thermostat to its lowest setting and drain the cylinder first

Explanation

Safe isolation means switching off the correct protective device, locking it in the off position with a personal lock and tag, and then proving the conductors dead with a tester that has been proved before and after the test. A thermostat is a control device and does not isolate the supply, and a colleague standing by the board gives no guarantee against another person restoring power. Draining the cylinder is a plumbing step, not an electrical safeguard.

Question 5Occupational Health, Safety and Workplace Practices

A technician must use a 230 V portable grinder to dress a pipe joint in a damp plant room. Which control most reduces the risk of a fatal electric shock?

  1. Standing on a dry timber board laid over the wet concrete floor
  2. Working quickly so the time spent in the damp plant room stays short
  3. Supplying the tool through a 30 mA RCD and checking the lead Correct answer.
  4. Wearing rubber-soled boots and dry cotton gloves throughout the whole task

Explanation

A 30 mA residual current device disconnects the supply within milliseconds if current leaks to earth, which is the control that actually limits the duration and magnitude of a shock; a damaged or wet supply lead is the most common trigger, so it must be inspected before use. Insulating footwear, gloves and dry standing boards only reduce the chance of a current path and are unreliable when floors are wet. Rushing the job also increases the chance of a mistake.

Question 6Occupational Health, Safety and Workplace Practices

A technician has just finished soldering a joint with a propane torch in a roof void containing timber and old pipe lagging. What fire precaution must be maintained after the flame is out?

  1. Keep a fire watch for at least 30 to 60 minutes after the flame is out Correct answer.
  2. Rely on the torch's flame-failure device to prevent any risk of fire
  3. Open all roof vents so that any smouldering material is cooled by draughts
  4. Wet down the timber once and leave the void straight after packing up

Explanation

Heat conducts along metal pipe and into lagging, so smouldering can start minutes after the torch is switched off and may not be visible at once. A fire watch of at least 30 to 60 minutes in the work area, with a suitable extinguisher to hand, is the standard hot-work control. Draughts from open vents supply oxygen and can spread a fire rather than cool it.

Question 7Occupational Health, Safety and Workplace Practices

While replacing a corroded service pipe in a 1950s house, a technician finds the pipe is made of lead. Which precaution is correct for this work?

  1. Heat the pipe gently first so the lead softens and cannot become airborne
  2. Wear a simple dust mask only while hacksawing the pipe to length
  3. Wet-cut or use a P3 mask and gloves, and never dry-sweep the dust Correct answer.
  4. Dry-brush the pipe ends, since lead dust is too heavy to be inhaled

Explanation

Lead is a cumulative poison that damages the nervous system and kidneys, and scraping, grinding or dry sweeping creates fine respirable dust and contaminated waste. Wet cutting methods, an FFP3 (P3) respirator, gloves and strict hand washing before eating or smoking keep exposure low. Heating lead produces fume, which is even more readily absorbed than dust.

Question 8Occupational Health, Safety and Workplace Practices

A technician is asked to use an unfamiliar two-part chemical drain-cleaning product in a basement. What should be consulted first, before the container is opened?

  1. The manufacturer's website gallery showing the product in use
  2. The wholesaler's price list, which lists the strength of the product
  3. A colleague who has used a similar product on another site
  4. The safety data sheet and the label instructions for the product Correct answer.

Explanation

The safety data sheet is the primary source of hazard information for a chemical, covering its composition, health effects, required personal protective equipment, first-aid measures and incompatible substances. Drain cleaners often contain caustic soda or sulphuric acid, and mixing them with other chemicals can cause violent boiling, spattering or toxic gas. The label repeats the key handling and emergency information in short form for use at the point of work.

Question 9Occupational Health, Safety and Workplace Practices

A technician must enter a 1.2 m deep inspection chamber to rod a blocked drain serving a block of flats. Which statement about the entry is correct?

  1. A lit taper held at the cover is a reliable test for flammable gas
  2. The atmosphere must be tested before entry and monitored continuously Correct answer.
  3. Holding your breath during the descent removes the need for gas testing
  4. Chambers under 1.5 m deep are exempt from confined space controls

Explanation

A drainage chamber is a confined space whatever its depth, because sewage generates hydrogen sulphide and methane and consumes oxygen, and these conditions can change while the technician is inside. A calibrated multi-gas meter must be used before entry and kept running throughout, with a top man, rescue harness and tripod, and breathing apparatus available. A flame test is itself an ignition source and gives no reading of oxygen or hydrogen sulphide.

Question 10Occupational Health, Safety and Workplace Practices

A drainage trench 1.8 m deep is being excavated in sandy soil alongside a road, and a technician will need to work in it. Which control is required before entry?

  1. Only the spoil heap needs to be moved further back from the trench edge
  2. No extra control is needed if the trench is entered for under ten minutes
  3. Sides battered, shored or boxed, with spoil set back from the edge Correct answer.
  4. A ladder placed inside the trench gives adequate protection from collapse

Explanation

Sandy soil and road loading make collapse likely, and a cubic metre of soil weighs well over a tonne, so a person trapped by it can be crushed or asphyxiated within seconds. Trenches deeper than about 1.2 to 1.5 m require the sides to be battered to a safe slope, supported by shoring, or protected by a proprietary trench box, and spoil, materials and plant must be kept back from the edge. Short duration of entry does not reduce the collapse risk.

Question 11Occupational Health, Safety and Workplace Practices

A plumbing contractor issues 110 V centre-tapped-to-earth tools and a site transformer for work on a construction site. Why does this arrangement reduce the severity of an electric shock compared with a 230 V tool?

  1. It makes the tool safe to use inside a flammable atmosphere.
  2. It removes the need to inspect and test the tool leads and plugs.
  3. It limits the maximum voltage to earth to 55 V. Correct answer.
  4. It lets a 230 V tool run at half speed so that it draws less current.

Explanation

A 110 V centre-tapped-to-earth supply gives a maximum of 55 V between either live conductor and earth, so the current that can flow through a person under fault conditions is much lower than on a 230 V system. It does not make a tool intrinsically safe in a flammable atmosphere, and routine inspection of leads and plugs is still required.

Question 12Occupational Health, Safety and Workplace Practices

A plumbing workshop keeps a 19 kg LPG cylinder for torch work. How should the cylinder be stored when it is not in use?

  1. Upright, secured and in a ventilated outdoor store. Correct answer.
  2. On its side in the back of the van with the regulator fitted.
  3. Standing beside the bench with the valve left open to save time.
  4. Lying flat inside a locked timber cupboard under the workbench.

Explanation

LPG is heavier than air and forms an explosive mixture in low areas, so a leaking cylinder indoors can accumulate gas at floor level. Cylinders are therefore kept upright and secured so that the valve is protected, with the valve closed, in a ventilated store away from ignition sources and occupied areas.

Question 13Occupational Health, Safety and Workplace Practices

A technician is solvent-welding PVC drainage pipe in a small, unventilated ground-floor bathroom. The primer and cement give off strong vapour. Which immediate control is most important?

  1. Standing the tin on a warm boiler casing to keep the cement flowing.
  2. Wearing a dust mask and keeping the door closed to stop draughts.
  3. Working faster so that the tin stays open for less time.
  4. Forced ventilation, removal of ignition sources, and a suitable respirator. Correct answer.

Explanation

Solvent cements and primers contain volatile flammable solvents whose vapour is heavier than air and can reach an explosive concentration in a small room. The priority is to remove vapour at source by ventilation and to keep flames, sparks and hot surfaces away; a respirator protects against inhalation but does not control the fire risk.

Question 14Occupational Health, Safety and Workplace Practices

A technician must reach a high-level pipe run above a stairwell and a mobile access tower has been supplied. Which condition must be met before the tower is climbed?

  1. The tower is pushed close to the wall while a second person holds the top.
  2. A ladder is placed on the platform to gain the last metre of height.
  3. All castors locked, the tower level, and guardrails and toe boards fitted. Correct answer.
  4. Only the two top guardrails are fitted so that materials can be passed up.

Explanation

A mobile tower is a work platform, so it must be stable before it is climbed: castors locked, ground firm and level, and a complete guardrail and toe board system in place. Towers must never be moved with a person or materials on the platform, and a ladder must not be placed on the platform to gain extra height.

Question 15Occupational Health, Safety and Workplace Practices

A technician uses an angle grinder for several hours a day dressing cast-iron pipe ends and notices tingling, numbness and whitening in the fingers. What do these symptoms indicate and what should be done?

  1. Normal tiredness that will settle after a weekend's rest, so no action is needed.
  2. Early hand-arm vibration syndrome; reduce trigger time, report it and arrange health surveillance. Correct answer.
  3. Dehydration from the working environment, so the technician should drink more water and continue.
  4. Electric shock from the grinder, so the tool should be provided with a better earth.

Explanation

Tingling, numbness and blanching of the fingers after prolonged use of vibrating tools are the early signs of hand-arm vibration syndrome, which can become permanent once established. Exposure should be reduced by limiting trigger time, using low-vibration tools and taking breaks, and the symptoms must be reported so that health surveillance can be arranged.

Question 16Occupational Health, Safety and Workplace Practices

A method statement for chasing pipe routes in a concrete ceiling lists 'issue P2 dust masks and goggles' as the first control for the silica dust hazard. How should this control measure be assessed?

  1. It is acceptable because PPE protects the individual worker directly.
  2. It is the correct first control because dust cannot be avoided when chasing concrete.
  3. It is acceptable provided the masks are fit-tested and changed every day.
  4. It is inadequate: suppress or extract the dust at source, and treat PPE as the last line of defence. Correct answer.

Explanation

Under the hierarchy of control, dust should first be eliminated or reduced at source, for example by wet suppression or on-tool extraction, before relying on administrative measures and PPE. A respirator protects only the wearer and depends on correct fit and use, so it is the last line of defence, not the first control.

Question 17Plumbing Tools, Materials and Fittings

In a galvanised iron (GI) water supply line, which fitting is screwed onto the ends of two pipes of equal diameter to continue the run in a straight line?

  1. 90° elbow
  2. Concentric reducer
  3. Socket Correct answer.
  4. Equal tee

Explanation

A socket, also called a coupling, has female threads at both ends and is run onto the two pipe ends so that the line continues straight. An elbow turns the line through a fixed angle and a tee opens a branch, so neither can carry a straight run forward. A reducer is used only where the bore changes.

Question 18Plumbing Tools, Materials and Fittings

Which tool is used by a plumber to cut external threads on the end of a GI pipe before it is screwed into a fitting?

  1. Pipe cutter
  2. Reamer
  3. Stock and die Correct answer.
  4. Flaring tool set

Explanation

A stock and die carries hardened die heads that are rotated onto the pipe end, which is first clamped in a pipe vice, cutting a tapered external thread for screwed fittings. A pipe cutter only severs the pipe to length and a reamer only cleans the bore. A flaring tool is used on soft copper for flare joints, not for cutting threads.

Question 19Plumbing Tools, Materials and Fittings

Which of the following pipes is the correct choice for an internal plumbing line carrying hot water at 60–80 °C?

  1. Rigid PVC
  2. HDPE
  3. uPVC
  4. CPVC Correct answer.

Explanation

CPVC is chlorinated polyvinyl chloride and keeps its pressure strength up to roughly 90 °C, so it is accepted for hot water distribution. uPVC and rigid PVC soften at around 60 °C and sag under hot water pressure. HDPE is normally restricted to cold water and underground service.

Question 20Plumbing Tools, Materials and Fittings

A copper tube has to be connected to a galvanised steel pipe in a water line. Which fitting breaks the metallic contact between the two pipes and prevents galvanic corrosion?

  1. Concentric reducer
  2. Dielectric union Correct answer.
  3. Brass hex nipple
  4. Compression union

Explanation

When copper and galvanised steel are in contact in the presence of water, a galvanic cell forms and the steel, being anodic, corrodes quickly. A dielectric union contains an insulating gasket or sleeve that interrupts the electrical path between the two metals, so the couple cannot drive corrosion. Ordinary brass or steel fittings still leave the metals electrically connected.

Question 21Plumbing Tools, Materials and Fittings

In which direction should PTFE tape be wrapped on a male pipe thread?

  1. Only on the first two threads
  2. Anticlockwise from the pipe end
  3. Clockwise from the pipe end Correct answer.
  4. Lengthwise along the thread

Explanation

The tape is wound in the same sense that the mating fitting turns when tightened, that is clockwise as seen from the end of the male thread. Wound this way the tape is pulled into the thread gap rather than unwound. Winding it the other way makes the fitting push the tape out of the joint as it is screwed on.

Question 22Plumbing Tools, Materials and Fittings

Which valve gives quick quarter-turn isolation with full bore and minimum pressure loss on a domestic water line?

  1. Gate valve
  2. Globe valve
  3. Ball valve Correct answer.
  4. Swing check valve

Explanation

A ball valve has a bored spherical plug turned through 90° by a lever, so it isolates fully in a quarter turn with little flow resistance. A gate valve needs many turns of the handwheel, and a globe valve is intended for throttling rather than quick isolation. A swing check valve allows flow in one direction only and cannot be used to shut off the line.

Question 23Plumbing Tools, Materials and Fittings

PPR (polypropylene random copolymer) pipes and fittings are joined in the field by which method?

  1. Heat fusion welding Correct answer.
  2. Solvent cement and primer
  3. Compression rings
  4. Screwed threads with PTFE tape

Explanation

PPR is a thermoplastic that is neither solvent cemented nor reliably threaded; the pipe end and the fitting socket are both melted on a heated fusion tool and pushed together. On cooling the two melt zones fuse into a single continuous wall, giving a joint as strong as the pipe. Solvent cement does not dissolve polypropylene.

Question 24Plumbing Tools, Materials and Fittings

After cutting a copper tube with a wheel-type pipe cutter, why is the end reamed before jointing?

  1. To remove the internal burr Correct answer.
  2. To harden the cut edge
  3. To widen the tube end for the fitting
  4. To mark the insertion depth

Explanation

The cutter wheel squeezes the metal and leaves a sharp burr on the inside of the tube, which narrows the bore, creates turbulence and erosion-corrosion, and can stop the tube seating fully in the fitting. Reaming restores the full bore and a clean edge. The outside end is usually also filed square before soldering or compression jointing.

Question 25Plumbing Tools, Materials and Fittings

A quick-closing solenoid valve at the end of a long horizontal line bangs loudly each time it shuts. Which device is fitted close to the valve to absorb the pressure surge?

  1. Temperature relief valve
  2. Vacuum breaker
  3. Pressure-reducing valve
  4. Water hammer arrestor Correct answer.

Explanation

When a fast-closing valve stops a moving column of water, the kinetic energy becomes a pressure surge that travels back along the pipe and produces the banging known as water hammer. An arrestor, or air chamber, provides a compressible cushion of air near the valve that absorbs the surge. Reducing valves, vacuum breakers and relief valves control pressure, backflow and temperature respectively, not shock.

Question 26Plumbing Tools, Materials and Fittings

Two fixed GI pipes at the same level must be joined, and neither pipe can be rotated. Which fitting allows the joint to be drawn up without turning either pipe?

  1. A straight coupling
  2. A three-piece union Correct answer.
  3. A reducing socket
  4. A hexagon nipple

Explanation

A three-piece union consists of two tail pieces and a central nut, so the tails are screwed into the fixed pipe ends and the nut is then tightened to pull the joint together without rotating either pipe. A coupling or socket is a single body that must itself be turned onto the thread of one pipe, which is impossible when both pipes are already fixed. A nipple simply extends a threaded connection.

Question 27Plumbing Tools, Materials and Fittings

In a GI water supply line, a 25 mm pipe has to continue as a 15 mm pipe. Which fitting is screwed onto the pipe end to make this change of size?

  1. A nipple
  2. A reducer Correct answer.
  3. A coupling
  4. A union

Explanation

A reducer is threaded with a larger bore at one end and a smaller bore at the other, so it screws onto the 25 mm pipe and accepts the 15 mm pipe. A coupling joins two pipes of the same nominal size and a union is a dismantling joint, so neither of them changes the diameter.

Question 28Plumbing Tools, Materials and Fittings

Which tool does a plumber use to grip and turn a GI fitting onto the threaded end of a pipe?

  1. A hand die stock
  2. A flaring block
  3. A pipe wrench Correct answer.
  4. A wheel-type tube cutter

Explanation

A pipe wrench (Stillson) has hardened serrated jaws and an adjustable opening, so it bites on a pipe or fitting and applies the turning force needed to screw it home. A die stock cuts external threads, a tube cutter parts the pipe and a flaring block forms flare ends.

Question 29Plumbing Tools, Materials and Fittings

Which copper–zinc alloy is widely used for taps, valves and plumbing fittings because it machines easily, takes a clean thread and resists corrosion?

  1. Cast iron
  2. Lead
  3. Mild steel
  4. Brass Correct answer.

Explanation

Brass is an alloy of copper and zinc that casts and machines well, accepts a clean thread and resists corrosion in water services, which is why taps, valves and many fittings are made from it. Cast iron, mild steel and lead are not copper–zinc alloys and each has different corrosion and working behaviour.

Question 30Plumbing Tools, Materials and Fittings

Which component of a brass compression fitting is crushed between the fitting body and the nut to seal against the copper tube?

  1. An O-ring inside the nut
  2. A capillary solder ring
  3. A fibre tap washer
  4. The olive (ferrule) Correct answer.

Explanation

When the nut is tightened onto the body it squeezes the soft copper or brass olive onto the outside of the tube, deforming it into a watertight seal. Fibre washers belong in tap connectors, a solder ring belongs to a capillary joint, and an O-ring is typical of push-fit fittings.

Question 31Plumbing Tools, Materials and Fittings

Which valve should be fitted on the discharge side of a booster pump so that water cannot run back through the pump when it stops?

  1. A globe valve
  2. A check (reflux) valve Correct answer.
  3. An air release valve
  4. A gate valve

Explanation

A check valve opens with flow in one direction and closes automatically as soon as flow reverses, so water cannot run back through the pump and make it spin backwards. Gate and globe valves are hand-operated isolating valves and an air release valve is used to vent trapped air, not to stop reverse flow.

Question 32Plumbing Tools, Materials and Fittings

At the foot of a vertical 100 mm soil stack the pipe turns into a horizontal drain. Which fitting gives a smooth, sweeping change of direction at this point?

  1. A rest bend Correct answer.
  2. A 90° square elbow
  3. A socket coupler
  4. A sanitary tee

Explanation

A rest bend is a long-radius bend, usually 87.5°, placed at the base of a soil stack so that solids and water change from vertical to horizontal flow smoothly without settling and blocking. A square elbow makes a sharp turn that encourages chokage, while a tee or coupler does not turn the line at the base.

Question 33Plumbing Tools, Materials and Fittings

Soft copper tube is to be connected to a flare fitting on a small water line. Which tool forms the 45° cone at the end of the tube?

  1. A swaging punch
  2. A deburring tool
  3. A tube bender
  4. A flaring block with a yoke and cone Correct answer.

Explanation

A flaring block clamps the tube squarely and a cone on the yoke is screwed down to press the tube end out into a 45° flare, which the flare nut then pulls against the fitting seat. A bender forms bends, a deburring tool removes the internal burr and a swaging punch expands a tube so another tube can be inserted.

Question 34Plumbing Tools, Materials and Fittings

Which joint is made simply by pushing the lubricated spigot end of a uPVC drainage pipe into the socket so that a rubber ring inside the socket is compressed?

  1. A heat-fusion joint
  2. A threaded joint
  3. A ring-seal push-fit joint Correct answer.
  4. A solvent-cement joint

Explanation

In a ring-seal joint a rubber sealing ring sits in a groove inside the socket; pushing the lubricated spigot in compresses the ring to give a flexible, watertight joint that also absorbs slight ground movement. Solvent cement, threading and heat fusion all need chemicals, dies or heating equipment rather than simple insertion.

Question 35Plumbing Tools, Materials and Fittings

A new 15 mm branch must be taken from an existing 50 mm PVC water main at a chosen point, without cutting out a full section of the main. Which fitting is used?

  1. A 50 × 15 mm reducer
  2. A 50 mm end cap
  3. A saddle clamp with a tapped outlet Correct answer.
  4. A 50 mm straight coupling

Explanation

A saddle clamp is strapped around the main and its tapped outlet is drilled through the pipe wall, so a branch can be taken at any convenient point without cutting in a tee. Reducers, couplings and end caps must all be inserted as part of the line and cannot create an outlet.

Question 36Plumbing Tools, Materials and Fittings

A length of hard-drawn copper tube keeps springing back and cracking when it is bent. What is the correct treatment before bending?

  1. Case-harden it by heating and quenching in oil
  2. Chill it in a refrigerator before bending
  3. Anneal it by heating to a dull red and cooling Correct answer.
  4. Hammer it along its length to soften it

Explanation

Hard-drawn copper is work-hardened, so it must be annealed by heating to a dull red and then cooling or quenching, which restores the soft ductile structure needed for a clean bend. Quenching in oil, hammering or chilling all leave the tube hard or brittle, and it will still crack or spring back.

Question 37Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

BSPT pipe threads are cut with a taper of 1 in 16. What does this taper achieve when the joint is made up?

  1. The joint seals only after PTFE tape is wrapped over it
  2. The pipe end seats metal-to-metal against a shoulder in the fitting
  3. The threads wedge together and seal along their flanks Correct answer.
  4. The thread can be cut in one pass with a fixed die

Explanation

A tapered thread increases in diameter along its length, so as the male thread is screwed into the female thread the flanks crush together and close the spiral leakage path. This wedging action is what makes a screwed joint with correctly cut BSPT threads capable of holding pressure once a suitable sealant is used.

Question 38Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

What is the main function of the primer applied to PVC pipe and fitting surfaces before solvent cement?

  1. It reacts with the cement to speed up evaporation of the solvent
  2. It softens and etches the surfaces so the cement can fuse them Correct answer.
  3. It lubricates the pipe so it slides into the socket easily
  4. It fills the clearance gap between the pipe and the socket

Explanation

Primer contains aggressive solvents that remove surface glaze, oil and contamination and partially soften the PVC. The softened surfaces allow the cement to dissolve and intermingle the plastic so that, after the solvent evaporates, the pipe and fitting become one continuous material.

Question 39Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

During capillary soldering of a copper tube and fitting, why is flux applied to the cleaned surfaces?

  1. It raises the tube temperature to the melting point of the solder
  2. It stops solder from entering the socket so the bore stays clear
  3. It fills the joint gap and acts as the jointing metal
  4. It removes oxide film and lets molten solder wet the copper Correct answer.

Explanation

Copper oxidises quickly when heated, and solder will not wet or flow over an oxide film. Flux dissolves the oxides and shields the metal from air until the solder is drawn into the joint clearance by capillary action.

Question 40Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

Which statement correctly distinguishes brazing from soldering when joining copper pipework?

  1. Soldering always produces a stronger joint than brazing on copper tube
  2. Brazing tolerates dirty copper because the flux burns away all scale
  3. Brazing uses a filler melting above 450 °C drawn in by capillary action Correct answer.
  4. Brazing uses a filler metal that melts below 450 °C and flows by gravity

Explanation

The accepted dividing line between soldering and brazing is a filler melting temperature of about 450 °C. Brazing fillers such as copper-phosphorus or silver alloys melt above that value, and like solder they are pulled into a correctly clearanced joint by capillary action rather than by gravity.

Question 41Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

When making up a screwed joint on galvanised steel pipe with PTFE tape, what is the correct practice?

  1. Wrap the tape clockwise on the male thread, leaving the first thread bare Correct answer.
  2. Wrap the tape over the whole male thread right up to the pipe end
  3. Apply the tape after tightening and work it into the open gap
  4. Wrap the tape anticlockwise on the female thread and fill the socket

Explanation

PTFE tape is wrapped in the direction of thread travel, clockwise when viewed from the pipe end, so tightening pulls the tape into the thread rather than unwinding it. Leaving the first one or two threads bare stops tape from being pushed into the pipe bore and contaminating the water.

Question 42Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

In socket fusion jointing of PP-R pipe, the parts are heated to about 260 °C and pushed together. What must be done immediately after the pipes are joined?

  1. Quench the joint in cold water to set the melt quickly
  2. Rotate the pipe a quarter turn to spread the molten plastic
  3. Wipe the bead of melted plastic away with a dry cloth
  4. Hold the joint steady and let it cool before any bending or turning Correct answer.

Explanation

Molten polypropylene has almost no strength, so the joint must be held aligned and undisturbed while it cools and crystallises. Bending, twisting or pressurising the joint during this period produces voids and a weak weld that may fail in service.

Question 43Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

A 40 mm PVC solvent-cemented joint assembled at 20 °C was pressure-tested 30 minutes later and pulled apart. What is the most likely cause?

  1. The pipe was given a quarter turn as it was inserted
  2. Too much cement was applied to the fitting socket
  3. The pipe end was reamed and chamfered before assembly
  4. The joint was tested before the cement had fully cured Correct answer.

Explanation

Solvent cement joints gain strength only as the solvent evaporates and the plastic re-forms; at 20 °C a 40 mm joint needs a much longer cure than 30 minutes before pressure testing. Testing early forces water into a joint that has not developed its full bond and can push it apart.

Question 44Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

Which practice produces a sound capillary solder joint on copper tube?

  1. Touch solder to the joint before the copper reaches solder temperature
  2. Leave a wide clearance between tube and fitting so solder can flow
  3. Heat the tube only and keep the flame off the fitting body
  4. Heat the fitting evenly and touch solder to the gap when the metal melts it Correct answer.

Explanation

Capillary soldering depends on the whole joint area reaching solder melting temperature so the filler flows freely into a close clearance. Heating the fitting evenly and testing with the solder at the mouth of the joint gives a reliable indication that the tube and socket are both hot enough.

Question 45Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

After brazing a copper-to-brass joint with a silver-based filler, a glassy residue remains around the fitting. Why must this residue be removed?

  1. It is brazing flux, which is corrosive and can eat into the joint Correct answer.
  2. It is hardened filler metal that would block the waterway
  3. It must be left in place to protect the joint from corrosion
  4. It insulates the pipe so the joint never cools down

Explanation

Silver brazing fluxes are chemically active and remain corrosive, particularly in the presence of moisture, so any residue must be taken off after the joint has cooled. Warm water and a brush or a mild scouring action is normally enough to remove it completely.

Question 46Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

Why should a back-up wrench be used on the fitting when tightening a screwed steel pipe joint?

  1. It keeps the pipe aligned until the sealant has set hard
  2. It holds the fitting against rotation so the pipe is not over-stressed Correct answer.
  3. It cuts the thread a little deeper as the joint is tightened
  4. It forces PTFE tape down into the roots of the thread

Explanation

Tightening a screwed joint applies torque to both the pipe and the fitting. Holding the fitting with a second wrench keeps that torque within the joint instead of twisting the pipe and straining the length of pipe or an upstream fitting, which can crack or loosen it.

Question 47Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

When cutting a BSPT thread on galvanised steel pipe with a die head, what is the main purpose of applying thread-cutting oil to the pipe and die?

  1. To strip the galvanised coating before the die starts cutting
  2. To swell the pipe so the thread fits more tightly
  3. To seal the finished joint against water pressure
  4. To cool the die and flush chips from the cut Correct answer.

Explanation

Thread-cutting oil lubricates and cools the die while carrying chips out of the cut. This gives a cleaner thread and reduces wear on the die. The oil is not a joint sealant and must not be relied on to stop leaks.

Question 48Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

Before soldering a copper tube into a capillary fitting, why is the cut end reamed?

  1. To remove oxide from the outside of the tube before fluxing
  2. To taper the tube end so it slides into the fitting more easily
  3. To roughen the outside surface so the solder grips better
  4. To remove the internal burr and keep the bore clear Correct answer.

Explanation

Reaming removes the raised burr left inside the tube by the cutter wheel. If the burr is left, it narrows the bore and can trap debris or cause turbulence. Reaming does not clean the outside of the tube; that is done with abrasive cloth before fluxing.

Question 49Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

What must be done to the pipe end and fitting socket immediately before solvent cement is applied to a PVC joint?

  1. Clean and dry both surfaces, then dry-fit and mark the depth Correct answer.
  2. Wrap the pipe end with PTFE tape so the cement can grip
  3. Coat both surfaces with oil so the cement does not set too quickly
  4. Heat the pipe end until it softens and then push it into the socket

Explanation

Solvent cement needs clean, dry, oil-free surfaces to dissolve and fuse the PVC. A dry fit checks that the pipe reaches the socket stop and shows how much insertion depth to mark. Oil, tape, or heat would prevent a proper solvent weld.

Question 50Pipe Joining and Fabrication (threading, soldering, brazing, solvent cement, fusion)

A fitter starts a die head on the end of a steel pipe at an angle and continues cutting the thread. What is the most likely result?

  1. A thread that automatically straightens as the die feeds along the pipe
  2. A skewed thread that will not make up square and is likely to leak Correct answer.
  3. A pipe that work-hardens so the die cannot finish the cut
  4. A stronger thread, because more metal is removed at the start

Explanation

The die must be started square to the pipe axis so the thread is cut concentrically. Starting at an angle produces a thread that runs off the axis, so the fitting sits crooked and the joint does not seal reliably. A die does not straighten itself once the cut has started off-square.