RBSE SS Voc Plumbing flashcards
RBSE SS Voc Plumbing · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Pipe wrench sizing
- A pipe wrench is sized by the pipe diameter it grips, not its overall length; a 350 mm wrench suits about 50 mm pipe. Pull the handle toward you for a firm bite.
- Basin wrench purpose
- A long, spring-loaded wrench with a pivoting jaw that reaches behind a lavatory bowl to loosen trap nuts and supply couplings where a standard wrench cannot fit.
- Reaming after cutting
- Removing the internal burr left by a tube cutter or hacksaw. A burr narrows the bore, increases turbulence, and promotes corrosion, so ream every cut before jointing.
- Die stock threading
- A hand tool holding a die that cuts external threads on steel pipe. Oil the die and reverse a quarter turn after each full turn to break chips and avoid torn threads.
- uPVC versus CPVC
- uPVC is rigid unplasticised PVC for soil, waste, and vent lines. CPVC is chlorinated PVC that also handles hot water up to roughly 80 to 90 degrees Celsius.
- PPR fusion jointing
- Polypropylene random pipe is joined by heating both pipe and fitting and pushing them together. The fused joint is stronger than the pipe wall and suits hot and cold supply.
- Solvent cement hazards
- PVC solvent cement is flammable and releases volatile organic compounds. Use it only with ventilation, away from flame, and wear gloves and eye protection.
- Confined space entry test
- Before entering a manhole or sump, test oxygen (19.5 to 23.5 percent), flammable gas, hydrogen sulphide, and carbon monoxide. Keep an attendant outside with a harness and tripod.
- Direct versus indirect supply
- Direct supply feeds fixtures from mains pressure. Indirect supply fills a storage tank from the mains, then gravity or a booster pump feeds the fixtures.
- Water hammer arrestor
- A device that absorbs the pressure surge when a valve closes suddenly. It is an air chamber or mechanical shock absorber installed close to the fixture.
- Backflow prevention
- Protection against reverse flow that could contaminate potable water. An air gap, reduced-pressure zone assembly, or double check valve is fitted at the cross-connection.
- Supply pipe velocity limit
- Water velocity in supply pipes is kept below about 1.5 to 2.0 metres per second. Higher velocity causes noise, erosion, and water hammer.
- Fixture unit values
- A fixture unit rates the load a fixture places on the drainage system. Typical values are 4 to 6 for a WC, 1 for a basin, and 2 for a sink or bath.
- Floor trap water seal
- A floor trap, often called a nahani trap, has a 50 mm water seal and a 50 to 75 mm outlet. It drains floor washing water and blocks sewer gas.
- Running flush cistern cause
- A cistern that keeps running usually has a worn float valve washer, a mis-set float arm, or a leaking flush valve seat, letting water pass continuously.
- WC trapway seal
- The water closet trapway must retain a water seal of at least 50 mm. This seal stops sewer gas entering the room while allowing waste to pass.
- Two-pipe drainage system
- Soil from water closets and waste from sinks and basins discharge into separate stacks. A one-pipe system combines them into a single stack with venting.
- Stack vent function
- The soil vent pipe continues full bore above the roof. It relieves pressure in the stack and discharges sewer gas above the building, protecting trap seals.
- Drain gradient rule
- Horizontal drains are laid at about 1 in 60 to 1 in 100 for 100 mm pipe. Too flat allows solids to settle; too steep leaves liquids behind.
- Inspection chamber placement
- An inspection chamber or manhole is provided at changes of direction, at junctions, and at intervals of 45 to 90 metres along a straight drain run.
- Isometric riser diagram
- A three-dimensional single-line drawing of pipework showing sizes, gradients, and fittings. It is the main working drawing for supply and drainage layouts.
- Invert level meaning
- The invert level is the height of the inside bottom of a pipe above a stated datum. Successive invert levels drop by the pipe gradient along the run.
- Drawing line conventions
- Solid thick lines show visible pipe, dashed lines show concealed or under-slab pipe, and centre lines mark pipe axes or symmetry. Symbols indicate valves, drains, and vents.
- Quantity take-off wastage
- When measuring pipe and fittings from drawings, add wastage allowances, commonly 5 to 10 percent on pipe and 2 to 5 percent on fittings, to cover offcuts and breakage.
- Rate analysis components
- A unit rate is built from material cost, labour cost, plant and tools, overheads, and contractor profit. It converts measured quantities into a priced bill.
- Bill of quantities content
- A BOQ lists each item with description, unit (metre, number, kilogram), quantity, rate, and amount. Measured quantities must agree with the drawings.
- Solvent joint leak repair
- A leaking solvent-welded joint cannot be tightened. Cut out the fitting and remake the connection using a coupling and new solvent cement.
- Water meter leak test
- Shut every fixture and watch the water meter. A moving dial indicates a hidden leak, often a running cistern, a dripping tap, or a buried supply line.
- Dye test for leaks
- Add dye to a cistern or trap and observe downstream. Dye appearing where it should not locates a broken seal or a cross-connection between systems.
- Trap arm vent limit
- The trap arm, the pipe between trap and vent, is limited in length, commonly 1.5 to 2.4 metres depending on size. A longer arm risks self-siphonage.
- Vent terminal height
- A vent pipe must terminate at least 150 mm above the roof surface and at least 3 metres from an operable window or fresh air intake.
- Legionella temperature control
- Store hot water at 60 degrees Celsius or above and distribute it at 50 degrees Celsius or above. Lukewarm water and dead legs allow Legionella to multiply.