Sri Lanka NVQ L3 Plumber flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ladder 4:1 rule

For every four metres of ladder height, the base sits one metre out from the wall. The ladder extends about one metre above the landing and is secured at the top before use.

Confined space entry rule

Any manhole, sump or septic tank is treated as oxygen-deficient until tested. Test the atmosphere, ventilate, use a permit, a standby person and rescue equipment before entry.

RCD protection value

Portable electrical tools on site should be protected by a residual current device rated at 30 mA. It disconnects quickly enough to reduce the risk of fatal shock.

Solvent cement fire hazard

Primer and solvent cement give off flammable, narcotic vapours. Keep ignition sources away, ventilate the space, and store cans closed and labelled.

BSP thread taper

BSP pipe threads are tapered at about 1 in 16. A correctly cut thread allows a female fitting to engage roughly three to four turns by hand before tightening.

Copper bend radius rule

The minimum bend radius for annealed copper is about three to four times the outside diameter. The pipe must be re-rounded after bending so the bore is not restricted.

Pressure gauge selection

Choose a test gauge whose range is about 1.5 to 2 times the test pressure. This puts the reading near mid-scale, where accuracy is best and over-pressurisation is visible.

Drawing revision control

Only the latest revision with the current issue date is used for construction. Superseded drawings are removed from site so old dimensions cannot be built by mistake.

Invert level definition

The invert level is the level of the inside bottom (soffit) of a drain. Cover level minus invert level gives the depth of excavation at that point.

Gradient 1 in 60

A fall of one unit per 60 units of run, equal to about 1.67 percent or 16.7 mm per metre. Fall in millimetres equals run in metres multiplied by 16.7.

Riser diagram purpose

A riser diagram shows vertical stacks, fixture connections, vents and the drain connection in diagrammatic form. It is not to scale and complements the floor plan.

Centre-line setting out

Mark the centre line of the fixture or stack first, then offset half the pipe outside diameter to each side. Marking only one edge causes misalignment.

Sleeve sizing rule

A sleeve through a wall or slab is at least 50 mm larger than the pipe it carries. This allows movement, insulation and fire-stopping without crushing the pipe.

Stack verticality tolerance

A soil stack should be plumb within the specified tolerance, commonly 5 mm over a storey height. Check two faces at 90 degrees with a level or plumb line.

Copper capillary jointing

Clean the pipe and fitting to bright metal, apply flux sparingly, and heat the fitting body until solder is drawn in. Let it set without movement and wipe off flux residue.

Compression fitting tightening

Insert the pipe fully past the olive seat, tighten finger-tight, then about one to one and a quarter turns with a spanner. Over-tightening splits the olive and crushes the pipe.

PTFE tape direction

Wrap PTFE tape in the direction the thread engages, clockwise on a right-hand thread. Leave the first two threads bare so the fitting starts cleanly without cross-threading.

Solvent weld procedure

Dry-fit and mark insertion depth, apply primer, then cement to both surfaces. Push fully home with a quarter turn, hold about 30 seconds, and do not disturb until cured.

Plastic thermal expansion

PPR and PE expand roughly 0.15 mm per metre per degree Celsius. Long hot runs need expansion loops or offsets, and sliding clips must not fully clamp the pipe.

Hydrostatic test pressure

Water pipework is tested at 1.5 times the working pressure or as specified, commonly a minimum of 10 bar held for one hour, with every joint inspected for leaks.

Legionella storage temperature

Hot water is stored at 60 degrees Celsius or above to control Legionella growth. A thermostatic mixing valve then delivers a safe outlet temperature at the fixture.

Backflow prevention method

Fit a check valve or provide an air gap between the potable mains and any non-potable or heating circuit. Temporary filling connections must be removed after use.

Water seal minimum

Every fixture trap must hold a water seal of at least 50 mm, and 75 mm for some gully and floor drain applications. A shallow seal allows sewer gas to pass.

Trap type selection

Use a P trap where discharge goes through the wall or floor behind, an S trap for a vertical drop below, and a bottle trap for an exposed basin. All traps must be accessible.

Appliance hose connection

Washing machine and dishwasher hoses connect to a tap fitted with a check valve, discharging into a trapped standpipe. This prevents backflow and sewer gas entry.

Branch connection angle

Connect a branch to a soil stack at 45 degrees or with a swept bend, not at a sharp 90 degrees. This keeps flow smooth and reduces the risk of blockage.

Air admittance valve rule

An AAV may replace a vent pipe only where the specification and manufacturer allow. It must be accessible and fitted above the flood level of the fixture served.

Drainage gradient range

Small-bore branches fall at about 1 in 60 to 1 in 80, and main runs at about 1 in 100. Never lay flatter than 1 in 150, or solids settle and the drain silts.

Water hammer cause

Water hammer is pressure surge from fast-closing valves or high velocity in undersized pipe. Cure it with an arrestor, correct sizing or slower-closing valves, not by tightening clips.

Trap seal loss diagnosis

A gurgling or smelly fixture usually loses its seal through self-siphonage, evaporation, wind pressure or a blocked vent. Cure the cause instead of only refilling the trap.

Isolation before repair

Close the nearest upstream valve, tag or lock it, drain the section, and confirm zero pressure at an outlet before opening any joint. Never rely on a closed valve alone.

Variation control rule

Any change to scope, material or programme is recorded as a variation with its cost and time impact and approved before work proceeds, except emergency safety measures.