WBCHSE HS Vocational 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 at a point due to the height of water above it. One metre of head equals about 9.81 kPa, so a 10 m head gives roughly 98 kPa.

Confined space entry test

Before entering a manhole, test for oxygen between 19.5 and 23.5 percent, and for hydrogen sulphide and methane. Use a standby person and harness.

Nominal bore

The standard size label for a pipe, such as 15, 20, 25 or 32 mm. It is close to, but not exactly, the internal diameter and fixes the thread size.

CPVC versus uPVC

CPVC withstands hot water up to about 93 degrees Celsius and is solvent-cemented. uPVC is for cold water and drainage only, limited to about 60 degrees.

Ductile iron pipe use

A strong, cement-lined pipe used for buried water mains. Joints are push-on or flanged, and it resists external loading and corrosion better than thin-wall pipe.

Pipe wrench use limit

A pipe wrench grips threaded steel pipe with serrated jaws. It must not be used on chrome-plated fittings or plastic, which it crushes and marks; use a strap wrench there.

Pipe cutter technique

A wheel cutter scores metal pipe and severs it. Tighten the wheel about a quarter turn per revolution and ream the burr afterwards to keep the bore clear.

BSP taper thread

Standard pipe thread with about a 55 degree angle and 1 in 16 taper. The taper makes the joint tighten and seal as it is screwed together.

Union fitting purpose

A fitting with three parts that lets a pipe run be disconnected without cutting. It is placed near valves and fixtures so maintenance is possible.

Y-branch versus tee

On drainage stacks a 45 degree Y-branch gives smoother flow and fewer blockages. A tee is used mainly for vent connections where flow is not the issue.

Solvent cement procedure

Cut square, deburr, clean with primer, apply cement to both surfaces, insert with a quarter turn, hold 30 seconds, and wait 24 hours before pressure testing.

PTFE tape direction

Wind two to three turns clockwise on a right-hand thread, in the direction the fitting turns, so making up the joint tightens the tape instead of unwinding it.

Hydrostatic pressure test

Fill the installation, expel air, pressurise to 1.5 times working pressure, and hold for at least one hour. A gauge drop with no visible leak means trapped air or a leak.

Trap water seal

The depth of water held in a fixture trap that blocks sewer gas. It must be 50 to 75 mm and the trap must have an accessible cleaning cap.

One-pipe drainage system

A system where soil and waste water from all fixtures discharge into a single stack. Each fixture has its own trap and vent connection to protect the seal.

Inspection chamber spacing

An access chamber placed at every change of direction, at junctions, and at intervals not exceeding about 15 metres on straight drain runs for rodding.

Overhead tank capacity rule

Allow about 100 to 150 litres per person per day for domestic use, and size the tank to hold at least one day of demand for the occupants.

Air gap on tank inlet

The float valve inlet must discharge above the overflow level with a clear gap, so backflow cannot contaminate the supply if pressure is lost.

Fixture unit method

A way to size supply pipes. Each fixture is given units, such as 3 for a WC and 1 for a basin, and the total sets the pipe size.

Meter leak test

Close all outlets, note the water meter reading, wait 15 to 30 minutes, then re-read. Any movement shows an undetected leak or a passing float valve.

Acoustic leak detection

Finding a hidden leak by listening with a stick or ground microphone for the loudest noise. It works best at night when background noise is lowest.

Running WC diagnosis

A pan that keeps running usually has a perished flush valve washer or a faulty ball cock. A dye test in the cistern shows water passing into the pan.

Centre-line measurement rule

Plumbing pipe work is measured along the centre line of the pipe, including fittings, but the pipe length inside a fitting is not measured separately.

Rate analysis for pipe work

Pipe cost per metre plus fittings apportioned per metre plus labour plus wastage plus overhead and profit. This gives the rate entered in the bill of quantities.

Retention money

A percentage, usually 5 to 10, held back from each bill and released after the defect liability period, commonly 6 to 12 months after completion.

Break-even job count

Fixed monthly costs divided by the difference between average job price and variable cost per job. The result is the number of jobs needed each month to break even.

GST registration threshold

In most Indian states a service provider must register for GST once annual turnover exceeds 20 lakh rupees. Registration is needed to issue tax invoices.

Job card contents

A record of site address, scope, materials issued, labour hours and customer signature. It is the main evidence for billing and for settling disputes.

Reaming after cutting

Removing the internal burr left by a pipe cutter. The reamer is turned clockwise with light pressure; the burr would otherwise raise flow resistance and trap sediment.

Cutting list purpose

A prepared list of all pipe lengths grouped by identical size, made before fabrication to reduce waste. Each piece is marked to match the drawing.

Wash basin connection set

Includes a 15 mm supply with stop cock, a 32 mm waste pipe, a P-trap with 50 mm seal, and a connection to the floor trap.

Workshop pre-start safety check

Inspect tool handles for cracks, confirm the grinder guard is fitted, check the fire extinguisher is charged, and clear the work area of trip hazards before starting.