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SOLAS Plumbing practice questions

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Question 1Health, Safety and Welfare on Plumbing Sites

On a plumbing refurbishment in a occupied building, which document must be completed before hot work such as soldering copper pipe begins, in order to control ignition risk?

  1. A hot work permit issued by the site controller Correct answer.
  2. A toolbox talk attendance sheet
  3. A COSHH assessment for the flux
  4. A manual handling risk assessment

Explanation

Hot work such as soldering, brazing or grinding creates ignition sources and must be controlled by a formal hot work permit system that records the location, fire precautions and fire watch arrangements. The permit is issued by an authorised person after the area has been checked and combustible materials removed or protected. Other assessments may also be needed, but they do not authorise the ignition source.

Question 2Health, Safety and Welfare on Plumbing Sites

A plumber must cut a section of cast iron soil pipe in a basement plant room. Which combination of controls best reflects the hierarchy of control for the dust produced?

  1. Wear a disposable dust mask and work quickly
  2. Wet the floor afterwards and open the plant room door
  3. Use a suitable extraction unit at the cut, supplemented by RPE if residual exposure remains Correct answer.
  4. Ask a colleague to stand nearby and warn people

Explanation

The hierarchy of control requires eliminating or reducing exposure at source before relying on personal protection. Local exhaust extraction captures dust at the cut point, and respiratory protective equipment is a last line of defence for any residual exposure. Simply issuing a mask without source controls does not follow the hierarchy.

Question 3Health, Safety and Welfare on Plumbing Sites

When a plumber discovers a suspect asbestos-containing board behind a pipe boxing in a pre-2000 building, what is the correct immediate action?

  1. Continue working and note it on the handover sheet
  2. Break off a small sample and bag it for the client
  3. Seal the board with tape and carry on with the task
  4. Stop work, isolate the area and report to the duty holder Correct answer.

Explanation

Suspect asbestos must be presumed to contain asbestos until proven otherwise, so work in the area must stop and the affected zone must be isolated to prevent fibre release. The duty holder or building manager must be informed so that a competent survey and, if needed, licensed removal can be arranged. Disturbing or sampling the material without training and controls is prohibited.

Question 4Health, Safety and Welfare on Plumbing Sites

Which statement correctly describes the purpose of a permit-to-work system for confined space entry during a drainage installation?

  1. It transfers legal responsibility to the permit issuer
  2. It guarantees the space is safe for the whole shift
  3. It replaces the need for atmospheric testing
  4. It records the persons authorised to enter and the precautions in place Correct answer.

Explanation

A permit-to-work is a formal record that authorises specific people to carry out defined work under stated precautions, and it documents isolation, testing and rescue arrangements. It supports safe systems of work but does not substitute for testing or remove anyone's legal duties. Conditions must be re-verified before and during entry.

Question 5Health, Safety and Welfare on Plumbing Sites

A plumber is about to use a gas-powered soldering torch in a small bathroom with the door closed. Which control most directly prevents a build-up of carbon monoxide?

  1. Using a longer torch hose
  2. Working in shorter bursts of ten minutes
  3. Providing forced or natural ventilation to the work area Correct answer.
  4. Wearing a half-mask respirator

Explanation

Carbon monoxide from an open flame or fuel-burning tool accumulates when the space is poorly ventilated, so providing ventilation removes the hazard at source. Respirators do not supply oxygen or filter carbon monoxide, and shortening the task only reduces exposure time without removing the risk. Ventilation is the primary engineering control.

Question 6Health, Safety and Welfare on Plumbing Sites

Which item of personal protective equipment is specifically required when handling and pouring a two-part chemical drain sealant?

  1. A high-visibility vest
  2. Chemical-resistant gloves and eye protection Correct answer.
  3. A bump cap
  4. Steel-toe boots only

Explanation

Two-part chemical products can cause skin burns and serious eye damage, so the safety data sheet will require chemical-resistant gloves and suitable eye or face protection. High-visibility clothing, toe protection and bump caps address different hazards such as vehicle movement, dropped loads and head strikes. The assessment should always be checked against the specific SDS.

Question 7Health, Safety and Welfare on Plumbing Sites

What is the minimum action a plumber should take when a 110 mm soil pipe must be carried up a ladder to a first-floor scaffold?

  1. Hoist or lift it mechanically rather than carrying it on the ladder Correct answer.
  2. Ask a colleague to push it up from below while climbing
  3. Cut it into shorter pieces and throw them up
  4. Carry it one-handed to keep the other hand on the ladder

Explanation

Carrying long or awkward loads on a ladder prevents the three points of contact needed for safe climbing and increases the risk of falls and dropped objects. Mechanical hoisting or a suitable lifting arrangement keeps both hands free and controls the load. Manual handling should be avoided where reasonably practicable.

Question 8Health, Safety and Welfare on Plumbing Sites

Before using a cartridge-operated nail gun to fix pipe clips to a concrete soffit, which check is most important for preventing a through-shot injury?

  1. Checking that the base material and cartridge power are suitable for the fixing Correct answer.
  2. Confirming the cartridge colour matches the brand
  3. Asking the client whether noise is acceptable
  4. Wearing ear defenders

Explanation

Through-shots occur when the cartridge power is excessive for the base material or the material is too thin or soft to stop the fastener. Selecting the correct cartridge and confirming the substrate is suitable is the key control before firing. Hearing protection and noise consultation are relevant but do not prevent penetration injuries.

Question 9Health, Safety and Welfare on Plumbing Sites

Which of the following best describes the correct use of a residual current device (RCD) with portable 230 V tools on a plumbing site?

  1. It should only be used outdoors
  2. It removes the need for visual inspection of plugs and leads
  3. It allows damaged leads to remain in use until the end of the shift
  4. It should be tested before use and used with 110 V or otherwise reduced-voltage equipment where practicable Correct answer.

Explanation

Site practice favours reduced low voltage such as 110 V centre-tapped-to-earth supplies, with RCD protection as an additional safeguard where 230 V equipment is used. The RCD must be tested using its test button and inspected regularly, and it never justifies using damaged leads. Visual checks of plugs and leads remain essential.

Question 10Health, Safety and Welfare on Plumbing Sites

A plumber is working alone in a plant room and needs to use a step ladder to reach a valve. Which practice is acceptable?

  1. Standing on the top two steps to gain extra height
  2. Placing the ladder on a loose board to level it
  3. Over-reaching sideways while keeping both feet on the step
  4. Using the ladder only for light work of short duration with the ladder set up correctly Correct answer.

Explanation

Step ladders are suitable for light work of short duration when they are stable, fully opened and on a firm level surface. Standing on the top steps, over-reaching or improvising with loose packing all compromise stability. Where the task is longer or heavier, a safer access platform should be provided.

Question 11Health, Safety and Welfare on Plumbing Sites

Which arrangement is the correct way to store compressed gas cylinders on a plumbing site?

  1. Lying horizontally in a locked store with valves open
  2. Upright and secured against falling, with valves closed and caps fitted where provided Correct answer.
  3. Stored loose in the site cabin to prevent theft
  4. Chained to a scaffold standard next to the hot work area

Explanation

Cylinders should be stored upright, secured to prevent them falling, with valves closed and protective caps fitted where provided. They should be kept away from ignition sources and separated according to the gas type and relevant guidance. Leaving valves open or storing cylinders loose creates serious uncontrolled release and impact risks.

Question 12Health, Safety and Welfare on Plumbing Sites

What is the primary purpose of a site induction for a plumber arriving on a new construction project?

  1. To explain site-specific hazards, rules and emergency arrangements Correct answer.
  2. To replace the need for task-specific risk assessments
  3. To confirm the operative's trade qualifications in detail
  4. To record the operative's working hours for payroll

Explanation

A site induction communicates the particular hazards, traffic routes, welfare arrangements and emergency procedures of that site, which a new arrival cannot know in advance. It complements, but does not replace, task-specific assessments and method statements. Qualification checks and payroll are separate processes.

Question 13Health, Safety and Welfare on Plumbing Sites

A plumber needs to enter a below-ground inspection chamber to rod a blocked drain. Which sequence best reflects a safe system of work?

  1. Test the atmosphere, then enter without any further checks
  2. Isolate and ventilate, test the atmosphere, then enter with a rescue plan and a competent person watching Correct answer.
  3. Ask a colleague to hold the cover open and enter alone
  4. Enter quickly to reduce the time spent in the chamber

Explanation

Confined space entry requires the hazard to be controlled first by isolation and ventilation, followed by atmospheric testing before entry. A competent person should remain outside, and a rescue plan with suitable equipment must be in place before anyone enters. Entering quickly or alone without these controls risks asphyxiation or drowning.

Question 14Health, Safety and Welfare on Plumbing Sites

Which statement about welfare facilities on a plumbing site is correct?

  1. Drinking water may be provided only if the site has more than twenty workers
  2. Washing facilities are needed only when lead pipe is being worked on
  3. Suitable toilets, washing facilities and drinking water must be provided from the start of the work Correct answer.
  4. Welfare provision can be deferred until the first fix is complete

Explanation

Suitable and sufficient welfare facilities, including toilets, washing facilities, drinking water and a place to rest and eat, must be provided from the outset of the work. Provision does not depend on the number of workers or the stage of the project. Plumbers handling soil, chemicals or lead have a particular need for washing facilities.

Question 15Health, Safety and Welfare on Plumbing Sites

When working with lead pipe and lead solder, which control is most important for preventing lead entering the body?

  1. Using a longer hacksaw blade
  2. Wearing a high-visibility vest
  3. Good personal hygiene, including washing hands before eating and drinking Correct answer.
  4. Working only in the afternoon

Explanation

Lead enters the body mainly by ingestion from contaminated hands, food, drink and smoking, and by inhalation of fume or dust. Strict hygiene, separate washing and no eating in the work area are therefore central controls, supported by extraction and RPE where fume is generated. Clothing choices and blade length do not address the exposure route.

Question 16Health, Safety and Welfare on Plumbing Sites

Which of the following is the correct interpretation of a safety data sheet for a solvent-based pipe cement?

  1. It only needs to be read by the site manager
  2. It is a substitute for a COSHH assessment
  3. It provides hazard, handling and first-aid information that informs the COSHH assessment Correct answer.
  4. It guarantees the product is safe if used outdoors

Explanation

The safety data sheet supplies hazard classification, exposure controls, first-aid and storage information that the employer uses to build the COSHH assessment. It does not itself constitute the assessment, because the assessment must also consider how the product is used on that site. Anyone using the substance needs access to the relevant information.

Question 17Health, Safety and Welfare on Plumbing Sites

Which action best demonstrates the correct response to a minor cut sustained while handling sheet metal ducting?

  1. Clean and dress the wound, report it and record it in the accident book Correct answer.
  2. Ignore it if bleeding stops within a minute
  3. Cover the cut with a plaster and continue, reporting it at the end of the week
  4. Rinse the cut with solvent to disinfect it

Explanation

Even minor injuries should be cleaned and dressed to prevent infection, and must be reported and recorded so that trends and causes can be identified. Prompt reporting also protects the worker if the injury later worsens. Using solvent on a wound causes further tissue damage.

Question 18Health, Safety and Welfare on Plumbing Sites

A plumber is asked to work in a room where a gas boiler has just been commissioned and a strong smell of gas is present. What is the correct immediate action?

  1. Light a match to locate the leak
  2. Turn the boiler up to burn off the gas
  3. Stop work, avoid operating switches, evacuate and raise the alarm Correct answer.
  4. Open a window and continue with the pipework

Explanation

A strong smell of gas indicates a leak that could form an explosive atmosphere, so work must stop and the area evacuated without operating electrical switches or flames. The alarm should be raised and the gas supply isolated by a competent person. Any ignition source, including a match or a boiler, must be avoided.

Question 19Health, Safety and Welfare on Plumbing Sites

Which method is appropriate for controlling the risk of falling when installing rainwater downpipes at the edge of a two-storey building?

  1. Using a suitable access platform or edge protection with the work planned from a safe position Correct answer.
  2. Leaning out from an open window while holding the pipe
  3. Balancing on a window sill with a colleague holding the ladder
  4. Standing on the top rung of a leaning ladder

Explanation

Work at height must be planned so that it can be carried out from a safe position, using a suitable platform, scaffold or edge protection rather than improvised balancing. Ladders are acceptable only for low-risk, short-duration work where a safer option is not justified. Leaning out of windows or standing on sills provides no fall protection.

Question 20Health, Safety and Welfare on Plumbing Sites

Which statement correctly describes the legal position when a self-employed plumber works alone on a domestic job?

  1. The self-employed plumber must protect themselves and others affected by their work Correct answer.
  2. The householder is responsible for all site safety
  3. Self-employed workers have no health and safety duties
  4. Duties only apply if the job exceeds one day

Explanation

Health and safety duties apply to self-employed people who conduct an undertaking, and they must protect themselves and anyone else affected by their work. Duration of the job and employment status do not remove these duties. The householder may have some duties as a client or domestic duty holder, but cannot absorb the plumber's responsibilities.

Question 21Health, Safety and Welfare on Plumbing Sites

Which control is most appropriate for reducing noise exposure when using a core drill on a concrete wall for several hours?

  1. Warning signs at the site entrance
  2. Rotating workers every ten minutes
  3. Providing ear defenders as the only control
  4. Selecting quieter equipment and using engineering controls, with hearing protection as a last resort Correct answer.

Explanation

Noise should be controlled at source by choosing quieter methods and using engineering measures such as enclosures or damping before relying on hearing protection. Job rotation and warning signs do not reduce the noise reaching the ears. Hearing protection is the final layer where exposure cannot be reduced sufficiently.

Question 22Health, Safety and Welfare on Plumbing Sites

A plumber is using a petrol-driven cut-off saw in a partially enclosed basement. Which hazard is most likely to be underestimated and requires specific control?

  1. Sunburn from daylight
  2. Slips from polished floors
  3. Noise from the client's radio
  4. Carbon monoxide from the exhaust Correct answer.

Explanation

Petrol engines produce carbon monoxide, which is colourless and odourless and can accumulate rapidly in enclosed or poorly ventilated spaces, causing unconsciousness and death. Specific controls include avoiding petrol equipment indoors, using ventilation and monitoring where appropriate. The other options are either not relevant to the task or trivial by comparison.

Question 23Health, Safety and Welfare on Plumbing Sites

Which of these behaviours best supports a positive health and safety culture among a plumbing gang?

  1. Leaving safety discussions to the supervisor alone
  2. Keeping quiet about minor defects to avoid delaying the job
  3. Reporting near misses and unsafe conditions without fear of blame Correct answer.
  4. Only reporting accidents that require time off work

Explanation

A positive culture depends on open reporting of near misses and unsafe conditions so that causes can be addressed before harm occurs. Blame-free reporting encourages workers to speak up, whereas hiding defects or reporting only serious injuries allows hazards to persist. Safety is a shared responsibility rather than the supervisor's alone.

Question 24Health, Safety and Welfare on Plumbing Sites

Which statement best explains why a plumber should check for buried services before digging a trench for a new below-ground drainage run?

  1. To decide which type of pipe to order
  2. To satisfy the client's insurance policy only
  3. To confirm the trench will be deep enough for the pipe
  4. To avoid striking electricity, gas or water services and causing injury or supply loss Correct answer.

Explanation

Striking a buried electricity cable, gas main or water pipe can cause fatal injury, fire, flooding or widespread supply loss. Service plans, cable avoidance tools and safe digging practice are used to locate and avoid services before excavation. The check is a safety control, not merely an administrative or ordering step.

Question 25Plumbing Science, Materials and Pipework Systems

In a marine freshwater cooling circuit, which material is most commonly specified for the seawater side of a shell-and-tube heat exchanger because of its resistance to chloride pitting and crevice corrosion?

  1. Austenitic 304 stainless steel
  2. Grey cast iron
  3. Galvanised mild steel
  4. 90/10 copper-nickel alloy Correct answer.

Explanation

Copper-nickel alloys, particularly 90/10 CuNi, are the standard choice for seawater-wetted surfaces because the nickel content stabilises the protective oxide film and resists chloride pitting and crevice attack. 304 stainless is vulnerable to chloride stress-corrosion cracking and pitting in seawater, and ferrous materials corrode rapidly without protection.

Question 26Plumbing Science, Materials and Pipework Systems

A pipe is described on a drawing as DN 80. What does this designation specify?

  1. The wall thickness grade of the pipe
  2. The outside diameter in millimetres exactly
  3. The internal bore in inches converted to millimetres
  4. A nominal size used for reference, not an exact dimension Correct answer.

Explanation

DN (diamètre nominal) is a dimensionless nominal size reference used to classify pipe and fittings; it does not correspond exactly to either bore or outside diameter. Actual dimensions are governed by the relevant standard and the schedule or wall thickness selected.

Question 27Plumbing Science, Materials and Pipework Systems

Which property of a plumbing material is measured by its resistance to indentation under a specified load and is used to compare the hardness of copper and copper alloys?

  1. Brinell hardness Correct answer.
  2. Modulus of elasticity
  3. Thermal conductivity
  4. Tensile strength

Explanation

Brinell hardness expresses resistance to indentation by a hardened ball under a defined load and is widely quoted for copper alloys. Tensile strength measures resistance to pulling apart, elasticity measures stiffness, and conductivity measures heat transfer, none of which describe indentation resistance.

Question 28Plumbing Science, Materials and Pipework Systems

In a potable water system on board, which pipe material is generally prohibited because lead can leach into drinking water?

  1. Lead-lined or lead-containing pipe Correct answer.
  2. Copper with lead-free solder
  3. 316L stainless steel
  4. Cross-linked polyethylene (PEX)

Explanation

Lead and lead-containing alloys are prohibited in potable water systems because lead leaches into the water and presents a serious health hazard. PEX, lead-free soldered copper, and 316L stainless are all accepted materials for potable service.

Question 29Plumbing Science, Materials and Pipework Systems

What is the primary purpose of a pipe schedule number such as Schedule 40 or Schedule 80?

  1. To identify the pipe's colour coding
  2. To indicate the pipe's end connection type
  3. To define the wall thickness relative to the nominal size Correct answer.
  4. To specify the maximum working temperature

Explanation

Schedule numbers define wall thickness for a given nominal size, with higher schedules giving thicker walls and higher pressure ratings. Colour coding, temperature limits, and end connection type are specified separately.

Question 30Plumbing Science, Materials and Pipework Systems

Which type of valve is best suited for throttling flow in a seawater cooling line where gradual regulation is required?

  1. Butterfly valve used fully open
  2. Globe valve Correct answer.
  3. Gate valve
  4. Non-return valve

Explanation

A globe valve has a contoured plug and seat that allows controlled throttling with good flow regulation. Gate valves are intended for isolation and suffer seat erosion when partly open, non-return valves only prevent backflow, and a fully open butterfly valve provides no regulation.

Question 31Plumbing Science, Materials and Pipework Systems

Which jointing method is normally used for small-bore copper pipe in a ship's freshwater system where a permanent, high-integrity joint is required?

  1. Capillary brazing or lead-free soldering Correct answer.
  2. Compression fittings only
  3. Push-fit plastic connectors
  4. Flanged connections

Explanation

Capillary joints using lead-free solder or brazing produce a permanent, high-integrity metallurgical bond for small-bore copper pipe. Push-fit and compression fittings are mechanical and less permanent, and flanges are used for larger or removable connections.

Question 32Plumbing Science, Materials and Pipework Systems

Which material is used for the body of a valve handling seawater because it resists galvanic corrosion when coupled with copper-nickel pipework?

  1. Cast iron
  2. Zinc-coated steel
  3. Aluminium bronze Correct answer.
  4. Mild steel

Explanation

Aluminium bronze is close to copper-nickel in the galvanic series, so a valve body of this alloy minimises galvanic corrosion when coupled to CuNi pipework in seawater. Mild steel, zinc-coated steel, and cast iron are much more anodic and would corrode rapidly.

Question 33Plumbing Science, Materials and Pipework Systems

A copper pipe carrying seawater is connected to a carbon steel bracket. What is the most likely corrosion mechanism at the junction?

  1. Crevice corrosion of the steel only
  2. Galvanic corrosion of the steel Correct answer.
  3. Stress-corrosion cracking of the copper
  4. Erosion-corrosion of the copper

Explanation

Copper and carbon steel form a galvanic couple in which the more noble copper acts as cathode and the anodic steel corrodes preferentially, especially in a conductive seawater environment. Stress-corrosion cracking and erosion-corrosion are not driven by the dissimilar-metal contact described.

Question 34Plumbing Science, Materials and Pipework Systems

What is the function of an expansion loop or expansion joint in a long run of hot water pipework?

  1. To absorb thermal movement and prevent excessive stress Correct answer.
  2. To increase the flow velocity in the line
  3. To act as a non-return device
  4. To provide a drain point at the lowest level

Explanation

Heated pipework expands, and an expansion loop or joint accommodates that movement so that thermal stresses and loads on anchors and equipment remain within acceptable limits. It does not affect velocity, drainage, or flow direction.

Question 35Plumbing Science, Materials and Pipework Systems

A section of pipework must be isolated for maintenance while the system remains under pressure. Which arrangement is most appropriate?

  1. A non-return valve
  2. A pressure relief valve
  3. A single gate valve
  4. Two isolation valves with a drain between them Correct answer.

Explanation

Double block-and-bleed isolation, using two valves with a drain between them, allows the section to be positively isolated and verified by opening the drain. A single valve may pass leakage, and non-return or relief valves do not provide isolation.

Question 36Plumbing Science, Materials and Pipework Systems

Which non-destructive test is most suitable for detecting internal porosity and lack of fusion in a welded pipe butt joint?

  1. Magnetic particle testing
  2. Visual inspection
  3. Dye penetrant testing
  4. Radiographic testing Correct answer.

Explanation

Radiographic testing reveals internal volumetric defects such as porosity and lack of fusion within the weld. Visual and dye penetrant methods detect only surface defects, and magnetic particle testing applies only to ferromagnetic materials and is surface/near-surface.

Question 37Plumbing Science, Materials and Pipework Systems

What is the main reason for specifying a higher Schedule pipe in a high-pressure compressed air line?

  1. To reduce the outside diameter of the pipe
  2. To increase wall thickness and pressure containment Correct answer.
  3. To improve the thermal conductivity
  4. To allow the use of push-fit joints

Explanation

A higher schedule number increases wall thickness for the same nominal size, raising the pressure containment capability of the pipe. It does not change the outside diameter, thermal conductivity, or the suitability of push-fit joints.

Question 38Plumbing Science, Materials and Pipework Systems

Which material is commonly used for flexible hose assemblies in a ship's low-pressure seawater and freshwater systems because it accommodates vibration?

  1. Braided stainless steel over a polymeric liner Correct answer.
  2. Solid copper tube
  3. Rigid cast iron
  4. Galvanised steel pipe

Explanation

Braided stainless steel over a polymeric liner provides flexibility to accommodate vibration and misalignment while retaining pressure capability. Rigid cast iron, solid copper, and galvanised steel are inflexible and transmit vibration to connected equipment.

Question 39Plumbing Science, Materials and Pipework Systems

A seawater pipe shows localised deep pitting beneath a rubber gasket at a flange face. Which mechanism best explains this?

  1. Uniform corrosion across the whole surface
  2. Galvanic corrosion from a dissimilar metal
  3. Erosion-corrosion from high velocity
  4. Crevice corrosion due to stagnant seawater in the gap Correct answer.

Explanation

Stagnant seawater trapped in the gap under a gasket becomes oxygen-depleted and forms a differential aeration cell, causing localised crevice corrosion. Uniform corrosion would affect the whole surface, erosion needs high velocity, and galvanic corrosion requires a dissimilar metal couple.

Question 40Plumbing Science, Materials and Pipework Systems

Which factor most strongly determines the pressure rating of a given thermoplastic pipe in a seawater system?

  1. The colour of the pipe
  2. The operating temperature and wall thickness Correct answer.
  3. The length of the pipe run
  4. The number of support brackets

Explanation

Thermoplastic pipe pressure ratings derate with increasing temperature, and the wall thickness (SDR) determines how much pressure the pipe can contain. Colour, run length, and support spacing do not set the pressure rating.

Question 41Plumbing Science, Materials and Pipework Systems

In a closed-loop freshwater heating system, what is the purpose of an air separator or automatic air vent?

  1. To remove entrained air that would cause poor circulation and corrosion Correct answer.
  2. To increase the system pressure above the relief setting
  3. To soften the water and prevent scale
  4. To provide a drain point for flushing

Explanation

Entrained air in a closed heating loop causes air locks, poor circulation, and corrosion, so an air separator or automatic vent removes it. It does not raise pressure, soften water, or serve as a drain.

Question 42Plumbing Science, Materials and Pipework Systems

Which pipe support arrangement is most appropriate for a long horizontal run of copper pipe subject to thermal expansion?

  1. Suspend the pipe with wire without any supports
  2. Use sliding supports with anchors at fixed points to guide expansion Correct answer.
  3. Support only at the two ends of the run
  4. Rigidly clamp every support to prevent any movement

Explanation

Sliding supports allow the pipe to move axially while anchors at fixed points direct expansion into the designed loops or joints, preventing excessive stress. Fully rigid clamping restrains expansion and can buckle or overstress the pipe, and inadequate support causes sag.

Question 43Plumbing Science, Materials and Pipework Systems

Which statement correctly describes the difference between a soldered and a brazed copper joint?

  1. Brazing is only used for plastic pipe
  2. Soldering uses filler that melts above 450 °C
  3. Brazing uses a filler that melts above 450 °C, giving a stronger joint than soldering Correct answer.
  4. Soldering requires no flux under any circumstances

Explanation

Brazing filler metals melt above approximately 450 °C, whereas soldering fillers melt below that temperature, so brazed joints are generally stronger and more heat-resistant. Soldering is not restricted to plastic pipe, and flux is often required to prevent oxidation.

Question 44Plumbing Science, Materials and Pipework Systems

What is the principal reason for using dielectric (insulating) unions between copper pipework and a steel tank?

  1. To increase the flow rate through the pipe
  2. To interrupt the galvanic couple and reduce corrosion of the steel Correct answer.
  3. To provide a pressure relief point
  4. To allow the pipe to expand freely

Explanation

A dielectric union breaks the electrical continuity between dissimilar metals, interrupting the galvanic cell that would otherwise drive corrosion of the anodic steel. It does not affect flow rate, thermal expansion, or pressure relief.

Question 45Plumbing Science, Materials and Pipework Systems

A pump suction line is being designed to avoid cavitation. Which piping practice is most important?

  1. Installing a non-return valve immediately at the suction inlet
  2. Keeping suction pipework short, large-bore, and free of high fittings losses Correct answer.
  3. Fitting a globe valve at the pump suction for throttling
  4. Reducing the suction pipe diameter to increase velocity

Explanation

Cavitation occurs when the pressure at the pump inlet falls below the vapour pressure of the liquid, so the suction line should be short, generously sized, and free of unnecessary fittings to minimise pressure loss. Throttling at the suction, reducing diameter, and adding resistance all worsen cavitation.

Question 46Plumbing Science, Materials and Pipework Systems

Two pipelines of identical bore carry the same fluid; one has twice the volumetric flow of the other. According to Darcy-Weisbach, how does the friction head loss change?

  1. It doubles
  2. It stays the same
  3. It halves
  4. It increases by a factor of about four Correct answer.

Explanation

Friction head loss is proportional to the square of velocity, so doubling the flow in the same bore quadruples the loss. Doubling, no change, or halving would apply only if the relationship were linear or inverse.

Question 47Plumbing Science, Materials and Pipework Systems

A copper-nickel seawater pipe is joined to a titanium heat exchanger tube plate. Which measure best controls galvanic corrosion of the CuNi?

  1. Increase the flow velocity through the joint
  2. Coat only the titanium surface with paint
  3. Remove all anodes from the system
  4. Use an insulating gasket and a sacrificial anode on the CuNi side Correct answer.

Explanation

Titanium is strongly cathodic to copper-nickel, so the CuNi becomes the anode and corrodes; an insulating gasket breaks the couple and a sacrificial anode protects the CuNi. Increasing velocity worsens attack, coating only the cathode is ineffective, and removing anodes removes protection.

Question 48Plumbing Science, Materials and Pipework Systems

Which statement about the hydrostatic test pressure for a newly installed pipework system is correct?

  1. It is normally set at a defined multiple of the design pressure and held for a specified period Correct answer.
  2. It replaces the need for any non-destructive weld inspection
  3. It is always equal to the normal working pressure
  4. It is applied only to plastic pipework

Explanation

Hydrostatic testing applies a pressure that is a defined multiple of the design pressure (commonly 1.5 times, subject to the applicable standard) and holds it for a specified period to reveal leaks and weaknesses. It is not limited to normal working pressure, is not restricted to plastic pipe, and does not replace weld inspection.

Question 49Plumbing Science, Materials and Pipework Systems

In a gravity-fed freshwater tank discharge line, the available head is limited. Which change most effectively increases the discharge flow without altering the tank height?

  1. Installing a globe valve partly closed
  2. Increasing the pipe bore to reduce friction loss Correct answer.
  3. Fitting a smaller-bore outlet
  4. Adding elbows to lengthen the route

Explanation

With a fixed head, flow is limited by friction loss in the line, so increasing the bore reduces loss and raises the discharge rate. Adding elbows, reducing bore, or throttling all increase resistance and reduce flow.

Question 50Plumbing Science, Materials and Pipework Systems

In a ship's copper-nickel seawater line, which pipe support detail most directly prevents crevice corrosion at the pipe surface?

  1. Welding a steel lug to the pipe and bolting it to the deck
  2. Using a plastic-lined or non-metallic clamp with a bedding strip Correct answer.
  3. Fitting a galvanised steel saddle clamped directly onto the pipe
  4. Packing the gap between pipe and clamp with greased steel wool

Explanation

Crevice corrosion in copper-nickel seawater service is driven by stagnant seawater trapped in tight gaps with depleted oxygen. A non-metallic lined clamp or bedding strip keeps the pipe surface exposed and free of trapped electrolyte. Direct metal contact also risks galvanic attack and mechanical damage to the pipe wall.