RBSE Sec Voc Plumbing flashcards

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

Static head pressure

Pressure produced by a column of water, calculated as P = ρgh. A 10 metre column of water generates roughly 98 kilopascals, which is about one kilogram-force per square centimetre.

Nominal bore

The approximate internal diameter used to label pipe and fitting sizes. The actual outside diameter differs by material and standard, so measure before choosing a fitting.

Pipe cutter wheel

A hardened cutting wheel that scores and severs copper or plastic pipe when rotated under pressure. Ream the burr after cutting so flow is not restricted and the joint seats properly.

Stock and die

A threading tool held in a pipe vice that cuts external screw threads on steel pipe. Use cutting oil and back off a quarter turn periodically to clear chips and avoid torn threads.

Dual flush cistern

A water closet cistern offering a reduced flush, often three litres, and a full flush of about six litres. It cuts water use while still clearing the pan on the full setting.

Pressure reducing valve

A valve that limits downstream pressure to a set value, protecting fixtures and reducing noise and water hammer where mains pressure is excessive.

Downfeed supply system

A storage tank at roof level feeds fixtures by gravity through downpipes. Available pressure equals roughly 9.81 kilopascals per metre of height difference, less friction losses.

Pressure test supply pipework

Pipework is filled and pressurised to about 1.5 times working pressure, then held for at least an hour. Any pressure drop indicates a leak that must be located and repaired.

Self-cleansing velocity

The minimum flow speed, around 0.6 to 0.75 metres per second, that keeps solids moving in a drain. Flatter gradients risk silting and blockages.

One-pipe drainage system

Soil and waste discharges share a single stack that connects to the drain. Each fixture trap is individually vented to prevent seal loss from pressure changes.

Trap seal depth

The vertical water depth in a trap that blocks sewer gas. It should be at least 25 millimetres and no more than 100 millimetres, with 50 millimetres being standard.

Air admittance valve

A one-way valve that admits air into the drainage system when pressure drops, protecting trap seals. It does not release foul air and must be installed where local rules permit.

Float valve

A valve operated by a buoyant float that maintains a constant water level in a storage tank. It closes the inlet when the tank is full and opens as water is drawn off.

Total pump head

The sum of static lift, friction losses in pipes and fittings, and the discharge pressure required at the outlet. The pump must deliver design flow at this total head.

Capillary soldering

Molten solder is drawn by capillary action into the narrow gap between copper tube and fitting. Clean surfaces, flux and even heating are essential for a sound joint.

Solvent cement joint

A joint formed by softening plastic pipe and fitting surfaces with solvent cement so they fuse. Apply cement to both surfaces, push together, quarter-turn and hold before curing.

Isometric plumbing drawing

A three-dimensional style drawing showing pipe routes, fittings and fixture connections at a single view. It helps the installer plan bends and count fittings before work starts.

Rate build-up

The process of calculating a unit price for a measured item from material cost, waste allowance, labour hours, plant and overhead, before adding profit margin.

Water meter leak test

With every outlet closed, the meter should stop registering flow. Continued movement indicates a leak in the supply pipework or a passing valve or cistern.

Drain snake

A flexible cable with a cutting head used to clear blockages in waste pipes and drains. Rotate it through the branch, then flush or jet to confirm full clearance.

Confined space gas test

Before entering a tank, pit or manhole, test oxygen between 19.5 and 23.5 percent and check for flammable and toxic gases. Ventilate and use a permit and attendant.

Residual current device

A protective device that trips when it detects a small earth leakage current, commonly 30 milliamperes. Use it on portable tools and temporary site supplies near water.

Rainwater harvesting yield

The collectable volume equals roof catchment area multiplied by annual rainfall and a runoff coefficient of about 0.8 to 0.9. Storage is then sized to demand and dry spells.

Greywater reuse

Wastewater from baths, basins and showers, filtered and disinfected for flushing or irrigation. It must be labelled non-potable and kept separate from drinking water pipes.

Fixture unit

A relative measure of the load a fixture places on the water supply or drainage system. Values are added to size pipes and stacks against a standard flow basis.

Hacksaw blade teeth

Blades are graded by teeth per inch, with 18 teeth for thick sections and 24 for thin pipe. Fit the blade with teeth pointing forward and keep tension firm to cut straight.

Backflow prevention

Devices such as air gaps, check valves and vacuum breakers stop contaminated water from flowing back into the potable supply. Fit them at every cross-connection risk.

Drain gradient

The fall per unit length of a drain, commonly 1 in 60 to 1 in 100 for a 100 millimetre pipe. Adequate fall maintains self-cleansing velocity without leaving solids behind.

Vent stack height

The vent pipe must terminate at least about 900 to 1000 millimetres above the roof surface and clear of windows within three metres to avoid foul air re-entry.

Tank chlorination dose

After cleaning, dose the tank with chlorine at roughly 50 milligrams per litre, allow 30 minutes contact, then drain, flush and retest before returning it to service.

Brazing temperature range

Brazing uses filler metals that melt above about 450 degrees Celsius but below the melting point of the parent metal, giving stronger joints than soft soldering.

Bill of quantities

A document listing measured work items with descriptions and units such as metres, numbers or square metres. Contractors price each item to build up a tender total.