Punjab PSEB Matric NSQF Plumbing (Assistant Plumber) cheat sheet

Pipe wrench jaws grip in one direction only: pull the handle toward the pipe to tighten the bite; push the other way and the jaws slip and round the fitting.

Wrench size must match pipe size: a 350 mm pipe wrench suits up to about 25 mm pipe; oversize wrenches crush thin copper and plastic.

Stillson (pipe) wrench, chain wrench and strap wrench: chain and strap types are used on polished or plastic pipe where jaw teeth would scar the surface.

Hacksaw blade selection: 18 TPI for thick wall and large diameter, 24 TPI general pipe work, 32 TPI for thin-wall copper and tubing.

Blowlamp work needs a fire watch: clear combustibles within 1 m, keep a dry powder extinguisher at hand, and never heat a closed or pressurised system.

Spirit level accuracy is quoted per metre (e.g. 0.5 mm/m); check it by reversing it on the same spot - the bubble must repeat.

Torque and force: a wrench handle extension multiplies force (moment = force x distance), so a 0.5 m handle with 200 N gives 100 N·m - do not exceed fitting ratings.

Tool care rule: wipe, oil and store wrenches with jaws slightly open; a dropped pipe wrench must be re-checked for a cracked frame before use.

GI pipe sizes are nominal bore (NB): 15, 20, 25, 32, 40, 50 mm; the NB is not the outside diameter, so measure OD and wall to identify an unmarked pipe.

GI pipe is joined by screwed sockets and fittings; the thread is BSP taper (1:16), giving a wedging seal that needs jointing compound or PTFE tape.

PVC-U pipe for cold water uses solvent cement joints; CPVC (chlorinated PVC) is used for hot water up to about 80–90 °C.

Solvent cement joint sequence: cut square, deburr, clean with primer, apply cement to both surfaces, push fully home with a quarter turn, hold 30 s, cure before pressure.

Copper joints: capillary solder fittings need flux and clean bright surfaces; compression fittings need an olive and must not be over-tightened.

HDPE pipe is joined by butt fusion or electrofusion; compression fittings are for small sizes and repairs only.

Fitting names: elbow (90°), bend (larger radius), tee (equal/reducing), reducer, coupling/socket, union (demountable), cap, plug, nipple, bushing.

Material compatibility rule: never directly join dissimilar metals such as copper and GI steel without a dielectric union - galvanic corrosion follows.

Direct (upfeed) system: mains pressure feeds all taps; needs adequate residual pressure and no storage. Indirect system: mains fills an overhead tank that feeds outlets by gravity.

Overhead tank height rule of thumb: about 1 m of head gives roughly 10 kPa (0.1 bar); a shower needs about 0.2–0.3 bar at the outlet.

Tank must have: inlet with float valve, overflow pipe, washout/drain, tight-fitting lid, and be above the highest outlet.

Distribution layout: main run at highest level, branches taken off downward; avoid long horizontal dead legs and air traps at high points.

Common pressures: domestic mains 1–3 bar; test pressure for concealed pipework is typically 1.5 times working pressure, held for at least 1 hour.

Stop valve (isolation) at entry, at the tank outlet, and at each WC/basin group; non-return valve where backflow is possible.

Pipe sizing depends on fixture units and velocity; keep velocity below about 1.5–2 m/s in small bore pipe to limit noise and erosion.

Air lock symptom: tap sputters or no flow after mains interruption - clear by opening the lowest outlet and letting air escape at the highest.

WC flush volumes: conventional cistern 9–10 L; dual flush commonly 6 L full / 3 L reduced; a siphon cistern needs a full flush to re-establish the siphon.

Wash basin waste is 32 mm (1¼ in); sink waste 40 mm (1½ in); WC soil connection 100 mm (4 in).

Trap seal depth: 25–75 mm water seal; 50 mm is the usual design value. A seal below 25 mm allows sewer gas through.

Fixture clearances commonly used: WC centre at least 380–400 mm from a side wall; basin rim about 800 mm above finished floor; WC seat about 400–430 mm.

Flush valve (flushometer) needs a minimum supply pressure (often about 1 bar) and a larger branch than a cistern; cisterns work on low pressure.

Overflow: a cistern must have an overflow/warning pipe discharging visibly outside; a blocked overflow is a common cause of flooding.

Anti-siphon rule: any outlet or flush valve must be protected against backflow with an air gap or vacuum breaker.

Fixture faults: continuous running cistern = faulty float valve or flush valve washer; weak flush = blocked rim holes or low water level.

Two-pipe system: soil and waste carried separately; one-pipe system: soil and waste share a single stack, with waste connections above the soil entry.

Single-stack system uses a 100–110 mm stack with a vent; the branch must enter above the stack's lowest bend and within defined limits.

Gradient rule: 100 mm drain laid at 1 in 60 to 1 in 100 (about 1–1.7%); 50 mm branch at 1 in 40 to 1 in 60. Too flat silts, too steep leaves solids behind.

Self-cleansing velocity in drains is about 0.6–0.75 m/s at design flow; minimum sewer velocity commonly 0.6 m/s.

Inspection chamber spacing: typically 45 m for 100 mm drains and 90 m for 150 mm and above, with a chamber at every change of direction, gradient or size.

Vent pipe purpose: equalises pressure in the stack so trap seals are not siphoned; a vent stack must terminate above roof level, clear of windows.

Gully trap holds a water seal and catches grit; a P-trap or bottle trap sits under each fixture.

Drain test: air test or water test - fill to the highest point for at least 30 minutes and check for loss and visible leaks before backfilling.

Cut square: mark around the pipe with a strip of paper or a pipe square; an out-of-square cut causes a leaking thread or a poor solvent joint.

Threading sequence for GI: secure in a pipe vice, cut, ream the burr, chamfer, apply cutting oil, then use a die head (1/2 in BSP = 14 TPI, 3/4 in = 14 TPI, 1 in = 11 TPI).

Thread length rule: cut thread long enough for the socket plus 2–3 exposed threads; too long bottoms in the fitting and leaks, too short gives insufficient engagement.

Bending: minimum bend radius for copper is about 3–4 times the outside diameter in the annealed state; use a spring or bender and support the pipe.

Bending allowance: total length = straight lengths + bend allowance; for a 90° bend the allowance is roughly 1.57 x radius of the centre line.

Cold bending of copper needs annealed (soft) temper; hard temper copper must be annealed or bent with a bender to avoid kinking.

Solvent cement joint: dry fit first, mark insertion depth, apply cement quickly, push home, quarter-turn, hold, and do not disturb for the stated cure time.

Pressure testing after jointing: isolate the new section, fill, expel air, pressurise to 1.5x working pressure, hold 1 hour, check all joints with soap solution.

Soap solution test: brush soapy water on a joint under pressure; bubbles indicate the leak. Never use a flame to find a gas or refrigerant leak.

Water test for drainage: plug the low end, fill to the highest branch, mark the level, wait at least 30 minutes; a falling level means a leak.

Pressure test for supply pipe: 1.5x working pressure (commonly 10–15 bar for small bore), held 1 hour; a small initial drop from pipe expansion is normal.

Leak on a screw joint: tighten no more than about a quarter turn; if it still leaks, dismantle, clean the thread, renew PTFE tape or compound.

Burst pipe emergency: close the nearest isolation valve or the main stop valve, drain by opening the lowest tap, then repair.

Frozen pipe: isolate, open the nearest tap, thaw from the tap end toward the freeze with warm air or cloths - never an open flame.

Noise diagnosis: hammering (water hammer) = loose pipe clips or a fast-closing valve; fit an arrestor or re-clip. Whistling = undersized or partly closed valve.

Maintenance schedule: inspect tank and float valve every 6 months, clean tank annually, check trap seals and rod drains as needed; record each visit.

PPE for plumbing: safety glasses when cutting/threading, gloves for solvent cement and drainage work, safety footwear, dust mask for chasing, ear protection when drilling.

Solvent cement and primer are flammable and give off harmful vapour: use only with ventilation, no flame, and keep the lid on the tin.

Confined space rule: a manhole or septic tank is a confined space - test the atmosphere for oxygen and toxic gas, use a harness and a standby person outside.

Electrical safety: 230 V tools on a residual current device (30 mA); no wet hands; treat all buried or concealed cables as live until proved dead.

Ladder rule: 4:1 ratio - base 1 m out for every 4 m of height; secure the top, keep three points of contact, never overreach.

Manual handling: lift with legs, keep the load close, and get help above about 25 kg; use a trolley for long pipe lengths.

Excavation: support trenches deeper than about 1.2 m in loose soil, keep spoil back at least 0.5 m from the edge, and barricade the opening.

Environmental rules: never discharge solvent or cement washings to a drain or soil; collect waste and used oil for authorised disposal, and report spills.

Scale reading: 1:50 means 1 mm on the drawing equals 50 mm real; multiply the scaled measurement by the denominator.

Plumbing drawing symbols: solid line = water supply, dashed line = drain/soil, circle with cross = floor drain, triangle = vent, gate symbol = valve.

Isometric layout shows pipe runs in three axes; a plan shows the horizontal layout and a riser diagram shows the vertical stack connections.

Pipe length estimate = measured run + allowances for bends, offsets and waste; add about 5–10% for cutting waste and small fittings.

Fitting count rule: each change of direction needs an elbow or bend, each branch needs a tee, and each fixture needs a trap and a stop valve.

Costing formula: total = sum of (quantity x rate) for material + labour (hours x rate) + overheads + profit; add GST/percentage as required.

Take-off order: pipes by size and material, then fittings by size and type, then fixtures, then consumables (tape, cement, solder, clips).

Bill of quantities must state the unit: metre for pipe, each/number for fittings and fixtures, kg for solder and cement - never mix units.

A work order should record customer name, address, date, complaint, work done, parts used, cost, and both signatures - this is the basis of a warranty claim.

Estimate vs quotation: an estimate is approximate and may change; a quotation is a fixed offer, so state which one you are giving.

Communication rule for a complaint: listen fully, repeat the problem back, state what you will do and when, then confirm the customer agrees.

Pricing for a small plumbing business: charge = material cost + labour time x hourly rate + travel + overhead share + profit margin.

GST and invoicing: a tax invoice must show supplier GSTIN, invoice number and date, description, taxable value, tax rate and total.

Customer handover: demonstrate the isolation valve location, explain maintenance, and leave the site clean - this drives repeat and referral work.

Record keeping: keep a simple cash book and a job register; separate business and personal money to know real profit.

Marketing basics for a plumber: a consistent phone number, vehicle signage, local referrals, and online listing with photos of completed work.