WBBSE Madhyamik Vocational Plumbing flashcards

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

Nominal bore (NB)

The approximate internal diameter used to designate a pipe size; for a given NB a heavier schedule means a thicker wall and a smaller actual bore.

Water seal depth

The vertical depth of water held in a trap that stops sewer gas entering a building; commonly 50 mm for soil fittings and 25 to 38 mm for waste fittings.

Self-cleansing velocity

The minimum flow velocity in a drain, about 0.6 metres per second, that keeps solids moving and prevents silt deposition; it is achieved by laying the drain to the correct gradient.

Soil pipe versus waste pipe

A soil pipe carries human waste from a WC, usually 100 mm nominal; a waste pipe carries sullage from sinks and basins, usually 32 to 75 mm.

Anti-siphon vent pipe

A pipe that admits air into the drainage system to equalise pressure and protect trap seals from being sucked out; it terminates above roof level, clear of windows.

Separate sewerage system

A drainage arrangement in which foul sewage and storm water are carried in two separate sewers, so that rainwater does not overload the treatment works.

Solvent cement joint

A joint for PVC-U or CPVC pipe made by cleaning both surfaces, applying solvent cement, pushing the spigot fully into the socket with a quarter turn, and allowing full cure.

PTFE tape use

A thin tape wrapped around male pipe threads, in the direction of the thread, to seal threaded joints in water lines; it is not a substitute for a correctly cut thread.

Pipe cutter reaming

The operation of removing the internal burr left by a pipe cutter with a reamer or half-round file, so that flow is not restricted and the joint seats squarely.

Galvanised iron pipe

Mild steel pipe coated with zinc by hot dipping to resist corrosion; it is joined by threaded sockets and used for exposed water supply and risers.

Direct water supply

A system in which each fixture is fed straight from the mains without storage; it depends on continuous mains pressure and gives no reserve during cuts.

Indirect water supply

A system in which water is stored in a tank and then distributed by gravity or a pump; it provides a reserve and a steady head at the fixtures.

Ball valve or float valve

A valve inside a flushing cistern or tank that opens as the water level falls and closes when the cistern is full, controlling the refill.

Water hammer

Banging and vibration in a pipe caused by sudden valve closure; it is controlled by an air vessel, an arrester, or slow-closing valves.

Gate valve versus globe valve

A gate valve isolates flow with little resistance when fully open; a globe valve regulates flow but adds resistance because the flow turns through the body.

Check valve

A non-return valve that allows flow in one direction only, used to prevent backflow and to protect the supply from contamination.

Pipe wrench size

The size marked on a Stillson wrench, such as 8, 10, 12, 14, 18, 24, 36 or 48 inches, indicates the pipe diameter range the jaws can grip.

Pipe vice

A bench-mounted vice with shaped jaws that holds pipe horizontally for cutting, filing, and threading without crushing or marking the pipe.

Hacksaw blade selection

Blade teeth per inch are chosen by wall thickness: 18 or 24 teeth per inch for general metal pipe, finer 32 teeth per inch for thin-wall copper and plastic.

Fire extinguisher classes

Extinguishers are chosen by fire class: water for wood and paper, foam or CO2 for oil and paint, CO2 or dry powder for gas and live electrical equipment.

Scale on a drawing

A ratio such as 1:50 or 1:100 that relates a drawn length to the real length; a measurement on a 1:50 drawing is multiplied by 50.

Bill of quantities

A priced schedule listing each item of work with its description, unit, quantity, rate, and amount; the total of the amounts gives the estimated cost.

Single-line plumbing drawing

A drawing in which each pipe run is shown as one line, giving the route and size but not the wall thickness; used for layout and estimation.

Quotation versus estimate

A quotation is a fixed price for specified work and is binding once accepted; an estimate is approximate and may change with the actual quantities and conditions.

Tax invoice contents

A proper tax invoice shows the supplier's name and GSTIN, invoice number and date, the customer's details, the description with HSN or SAC code, the taxable value, and the tax charged.

Job card

A record for each job giving the customer's name and address, the work required, materials used, labour hours, and the customer's signature on completion.

Stop-tap leak test

A method of locating a leak by closing the stop tap and watching the water meter; a meter that still turns with all taps closed indicates a leak on the supply side.

Dripping tap repair

A tap that drips at the outlet is usually cured by renewing the washer or ceramic cartridge; a drip at the spindle needs new gland packing or an O-ring.

Pressure test of pipework

A new water installation is tested at about 1.5 times the working pressure, held for at least an hour; any drop in pressure or visible leak fails the test.

Die threading sequence

Chamfer the pipe, oil it, start the die square, cut one turn forward and half a turn back to break the chip, then clean and check the thread with a gauge.

Support spacing for pipe

The interval between pipe brackets: about 2 metres for GI pipe up to 25 mm and about 3 metres for larger sizes; plastic pipe needs closer supports because it sags when hot.

Wash basin fixing height

The rim of a wash basin is normally fixed about 750 to 800 mm above floor level, with a 32 mm waste pipe connected through a trap to the drain.