WBBSE Madhyamik Vocational Plumbing cheat sheet

Plumbing is the trade of installing and maintaining pipework that carries water supply in and soil/waste water out of a building, plus the fixtures and fittings attached to that pipework.

Standard pipe wrench (Stillson) sizes 8", 10", 12", 14", 18", 24", 36", 48"; the wrench size refers to the pipe diameter range it grips, not its own length.

A hacksaw for metal pipe uses 18 or 24 teeth per inch blades; a finer blade (32 TPI) suits thin-wall copper and plastic, a coarser blade suits thick-wall steel.

Pipe vice holds pipe horizontally for cutting and threading; a chain vice is used for large-diameter or plastic pipe where jaw marking must be avoided.

Personal protective equipment for plumbing work: safety goggles when cutting/chipping, gloves for handling cement and hot work, safety footwear, and a respirator when solvent cement or lead joints are used.

A pipe cutter leaves a square, burr-free end and must be rotated one full turn per tightening; burrs must be reamed out before jointing to prevent flow restriction and turbulence.

Fire safety rule: a fire extinguisher is chosen by class - water (A) for wood/paper, foam or CO2 (B) for oil/paint, CO2 or dry powder (C and electrical) for gas and live electrical equipment.

First aid for a deep cut: apply direct pressure with a clean pad, elevate the limb, and do not remove an embedded object; for eye contact with solvent cement, flush with clean water for at least 15 minutes and seek medical help.

GI (galvanised iron) pipe is mild steel pipe hot-dip galvanised against corrosion; it is joined by threaded sockets and is still used for exposed water supply and risers.

PVC-U pipe is joined by solvent cement (a socket-and-spigot joint); CPVC withstands hot water up to about 90 °C and is joined the same way; uPVC is not for hot water.

Copper pipe is joined by capillary soldering (lead-free solder), compression fittings, or press fittings; it is measured by nominal bore but actual outside diameter differs (e.g. 15 mm nominal ≈ 15 mm OD in metric ranges).

CI (cast iron) soil pipe is joined by lead-caulked spigot-and-socket or by rubber ring push-fit joints; it is used for soil and rainwater pipes for its strength and sound damping.

Thread standards: BSP (British Standard Pipe) threads are used on GI fittings; a 1/2" BSP thread has 14 threads per inch, 3/4" has 14, 1" has 11, 1 1/4" has 11, 1 1/2" has 11, 2" has 11.

Standard fitting names: elbow (90° bend), bend (larger radius), tee (branch), cross, reducer, coupling/socket, union (demountable joint), cap, plug, and nipple.

Solvent cement jointing sequence: cut square, deburr, clean with solvent cleaner, apply cement to both surfaces, push fully home with a quarter turn, hold 30 seconds, and allow full cure before pressure testing.

Nominal bore (NB) is the approximate internal diameter designation; for a given NB, higher schedule or heavier class means thicker wall and smaller actual bore.

Direct supply: water is drawn directly from the mains to each fixture; it depends on adequate mains pressure and is unsuitable where supply is intermittent.

Indirect supply: water is stored in an underground or overhead tank and then distributed by gravity; it gives a reserve and steady head but needs a pump or sufficient tank height.

A water tank must be covered, insect-proof, and have an overflow pipe and a washout/drain pipe; the overflow must not discharge onto a wall or into a drain without an air gap.

A wash basin is fitted with a 32 mm waste pipe, a WC pan with a 100 mm soil pipe, and a floor trap or gully with 50–75 mm waste pipe as typical practice.

A flushing cistern holds about 10 litres (older high-level) or 5–6 litres (low-level/dual-flush); the ball valve (float valve) refills it and the siphon or flush valve discharges it.

Water hammer is caused by sudden valve closure and is controlled by an air vessel, water-hammer arrester, or slow-closing valves; symptoms are banging pipes and vibration.

A tap's flow rate and pressure requirement are set by the fixture: a bib tap and pillar tap work at low head, while a shower needs a minimum head (often about 1 m above the rose) for adequate flow.

A gate valve isolates flow with low resistance when fully open; a globe valve regulates flow but adds resistance; a check valve (non-return valve) prevents backflow in a supply line.

A trap holds a water seal of 25–50 mm (commonly 50 mm for soil fittings, 25–38 mm for wastes) to stop sewer gas entering the building.

A P-trap has the seal in line with the pipe, an S-trap has two bends and is prone to self-siphon, and a bottle trap is used under basins where space is limited.

A soil pipe carries human waste from the WC (100 mm nominal), a waste pipe carries sullage from sinks and basins (32–75 mm), and a rainwater pipe carries roof water; the three must not be confused.

The drain must be laid to a self-cleansing gradient: 1 in 40 to 1 in 60 for 100 mm pipe and 1 in 60 to 1 in 100 for 150 mm pipe in typical practice, so flow velocity stays above 0.6 m/s.

A manhole is provided at every change of direction, at every junction, and at intervals not exceeding about 30 m, so the drain can be rodded and inspected.

The vent pipe (anti-siphon or soil vent pipe) equalises pressure in the drainage system and prevents trap seal loss; it must terminate above roof level, clear of windows.

A gully trap receives waste from a kitchen sink or floor and has a seal; a grease trap is fitted before the drain from a commercial kitchen to stop fat blocking the sewer.

Sewerage systems: separate system carries sewage and storm water in separate pipes, combined system carries both in one sewer, and partially separate systems take roof water separately but allow some surface water into the foul sewer.

Plumbing drawings use standard symbols: a circle with a cross for a floor drain, a small circle for a bib tap, a square with a diagonal for a cistern, and a filled triangle for a gully trap.

Scale is written as a ratio (1:50, 1:100); a length on a 1:50 drawing is multiplied by 50 to get the real dimension.

A single-line diagram shows the route of pipework; a double-line drawing shows the pipe wall thickness and is used for fabrication and for large-diameter work.

A bill of quantities lists each item with its description, unit (m, m², m³, number, kg), quantity, rate, and amount; the total of the amount column gives the estimated cost.

Pipe lengths are measured along the centre line of the run, and fittings are counted as numbers; the pipe length must not be reduced for the space taken by fittings in a simple estimate.

Labour cost is estimated as a percentage of material cost or by mandays; in small plumbing estimates, labour is often taken as 15–25% of the material cost.

Contingency and overheads are added after the net cost: overheads may be 5–10%, and contingency 3–5%, before profit is added.

A bar bending schedule or pipe schedule lists each pipe run with its size, length, fittings, and support spacing so that material can be ordered and issued to the site.

A leak on a concealed pipe is first located by isolating sections with valves and observing the meter; a stop-tap test shows whether the leak is on the supply or the internal line.

A water meter that keeps turning with all taps closed indicates a leak on the supply side; a hissing sound or a damp patch on a wall points to a concealed leak.

A leaking threaded joint is repaired by dismantling, cleaning the threads, applying new PTFE tape or jointing compound, and re-tightening - never by over-tightening, which splits the socket.

A leaking soldered copper joint must be cut out and re-made; solder cannot be reliably added to a failed joint without remaking it.

A dripping tap is usually cured by replacing the washer (jump valve) or the ceramic cartridge; a tap that drips from the spindle needs new gland packing or an O-ring.

A continuously running WC is diagnosed by checking the ball valve float setting, the siphon diaphragm, and the flush valve seal; a worn inlet washer or a distorted seal is the usual cause.

A blocked drain is cleared with a plunger, a drain rod, or a flexible auger, working from the nearest access point; chemical cleaners are a last resort and must never be used with a plunger.

A frozen or air-locked pipe is cleared by warming gently and by opening the highest tap to release air; a blowlamp must never be used on a plastic pipe or near a solvent-cemented joint.

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

A work order or job card records the customer's name, address, the work required, materials used, labour hours, and the customer's signature on completion.

GST registration thresholds and rates are set by law and change; a plumber must check the current threshold before charging tax on a bill, and a proper tax invoice shows GSTIN, invoice number, date, and HSN/SAC code.

A small plumbing enterprise needs a licence or trade registration where the local authority requires it, plus public liability insurance for work on occupied premises.

Basic bookkeeping separates material cost, labour cost, and overheads; a simple cash book and a job-wise ledger show whether each job made a profit.

Customer-care rules: arrive at the agreed time, protect floors and furniture with dust sheets, explain the fault before starting, and give a written bill with a warranty period.

Marketing for a plumbing business relies on referrals, local advertising, and a visible, well-lettered vehicle; a portfolio of completed work and photographs supports quotations.

Occupational safety duties of an employer include providing PPE, training, a first-aid box, and safe tools; a self-employed plumber owes the same duty to the client's household.

Bench work sequence for a pipe joint: measure, mark with a pipe square, cut with a hacksaw or cutter, file square, ream the burr, then thread or cement.

Threading with a die: secure the pipe in a vice, chamfer the end, apply cutting oil, start the die square, cut one turn forward and half a turn back to break the chip, then clean and test with a gauge.

A test pressure for a new water installation is typically 1.5 times the working pressure, held for at least one hour with no drop; a visible leak fails the test immediately.

A soil pipe test uses a air or water test on the drain with the lower end plugged; the test pressure for a drain is usually a 1.5 m head of water at the highest point.

Support spacing: GI pipe up to 25 mm is supported at about 2 m intervals, larger sizes at about 3 m; plastic pipe needs closer supports because it sags when hot.

A simple workshop project is a wash-basin installation: mark the height (about 750–800 mm to the rim), fix the bracket, connect the 32 mm waste to the trap, and connect the 15 mm supply with a stop tap.

A pipe vice must be mounted at about elbow height; a hacksaw cut is made close to the vice jaws to reduce vibration, and the blade is fitted with teeth pointing forward.

A project report records the drawing, the material list with quantities, the sequence of operations, the tools used, the test result, and the time taken for each operation.