RBSE SS Voc Plumbing cheat sheet

Pipe wrench: jaws grip and turn pipe; size is rated by the pipe diameter it fits (e.g., 350 mm wrench for 50 mm pipe). Always pull the handle toward you, not push.

Stillson (pipe) wrench teeth are directional - the jaw teeth point in the direction of rotation when the handle is pulled; reversing the grip gives poor bite.

Basin wrench: long, spring-loaded jaw reaches behind a lavatory bowl to loosen trap nuts where a normal wrench will not fit.

Flaring tool set: 45° flare for copper water lines; the cone is pressed into the tube end to form the flare, then the flare nut is tightened onto the fitting.

Tube cutter: score-and-snap wheel for copper; ream the inside burr after cutting or flow is reduced and turbulence/corrosion increases.

Threading: hand die stock with 15–50 mm dies cuts BSP/NPT external threads; apply cutting oil and reverse a quarter turn every full turn to break chips.

Level and plumb bob: check slope of drainage runs (typically 1:60 to 1:100 for 100 mm pipe) and verticality of stacks.

Pressure testing pump (hydrostatic tester): fills system with water and pressurises to check joints before concealment; gauge must be calibrated.

GI (galvanised iron) pipe: mild steel with zinc coating; used for cold water and some drainage, joined by threaded fittings. Zinc resists corrosion but is attacked by acidic water.

uPVC: rigid unplasticised polyvinyl chloride for soil, waste, and vent; joined by solvent cement. CPVC handles hot water up to about 80–90 °C.

PPR (polypropylene random): heat-fusion socket welded; used for hot and cold water supply; fusion joint is stronger than the pipe wall.

Copper: Type L for domestic water, Type K for underground; joined by soldering (lead-free solder), brazing, or press fittings.

Cast iron soil pipe: joined by lead-and-oakum caulking (traditional) or no-hub couplings; heavy, quiet, and fire-resistant.

PPE for plumbing: safety glasses when cutting/threading, gloves for solvent cement and caustic drain chemicals, respirator for PVC cement vapours in confined spaces, steel-toe boots.

Solvent cement is flammable and gives off VOCs - use only with ventilation; never near open flame.

Confined-space entry (manholes, sumps): test for oxygen (19.5–23.5%), LEL, H2S, CO before entry; attendant outside; harness and tripod.

Direct supply: mains pressure feeds fixtures directly; indirect supply: mains fills an overhead/underground tank, then gravity or a pump feeds fixtures.

Minimum residual pressure at a fixture: typically 0.5–1.0 bar (5–10 m head) for satisfactory flow; below this, a booster pump is used.

Pipe sizing uses fixture units and equivalent length; velocity in supply pipes should stay below about 1.5–2.0 m/s to limit noise and erosion.

Water hammer: caused by sudden valve closure; arrested by an air chamber or a mechanical shock absorber installed near the fixture.

Air lock in a gravity line is cleared by venting at the highest point or by re-priming; a continuous upward slope prevents trapping air.

Cross-connection control: a backflow preventer (air gap, RPZ, or double check valve) is required wherever a non-potable source could reverse-flow into the potable line.

Fitting take-off: 90° elbow changes direction, tee branches, reducer changes diameter, union allows disassembly, coupling joins two plain ends.

Pressure test of supply pipework: fill, purge air, pressurise to 1.5× working pressure (or code-specified value) and hold; no drop means sound joints.

Water closet (WC): wash-down or siphon type; trapway water seal must be 50 mm minimum to stop sewer gas.

Wash basin (lavatory): supplied through a 15 mm branch; waste 32–40 mm; overflow channel must drain into the trap, not outside it.

Floor trap (nahani trap): 50–75 mm trap with 50 mm water seal; used where a floor drain is needed and a P-trap cannot be fitted below.

Fixture unit (FU) values: WC = 4–6 FU, wash basin = 1 FU, sink = 2 FU, bath = 2 FU, floor trap = 1 FU (values vary by code; check local schedule).

Flush cistern: float valve (ball valve) refills; flush valve or siphon flushes; a running cistern usually means a worn washer or mis-set float.

Bidet, urinal, and drinking fountain each need their own trap and backflow protection; urinals use flushometer or cistern flush.

Accessibility: grab bars, 750–800 mm WC seat height for ambulant users, and lever handles; clear floor space in front of fixtures.

Fixture spacing: minimum 450 mm from a WC centre to a side wall; 150 mm clearance from fixture edge to adjacent wall for basins.

Two-pipe system: soil (WC) and waste (sinks, basins) discharge into separate stacks; one-pipe system combines them with a single stack and vent.

Stack vent (soil vent pipe) continues full bore above the roof to relieve pressure and let sewer gas escape above the building.

Trap seal: 50 mm water seal prevents sewer gas entry; a trap is required at every fixture and floor drain.

Vent pipe sizing: a 100 mm stack normally needs a 50–75 mm vent; relief vents are needed on stacks taller than about 10 storeys.

Self-siphonage is prevented by venting; induced siphonage is prevented by anti-siphon traps or a common vent.

Drain slope: 1:60 to 1:100 for 100 mm pipe; too flat causes solids deposition, too steep leaves liquids behind.

Inspection chamber (manhole): provided at changes of direction, at junctions, and at intervals of 45–90 m on straight runs.

Grease trap: intercepts kitchen fats before the sewer; sized by flow rate and retention time (typically 30 minutes).

Plan view: top-down layout showing fixture positions, pipe routes, and dimensions; the scale is stated in the title block (e.g., 1:50).

Isometric (isometric riser diagram): three-dimensional single-line drawing showing pipe sizes, gradients, and fittings; used for supply and drainage layouts.

Section/elevation: shows vertical pipe runs, invert levels, and stack heights; invert level = bottom inside of pipe.

Symbols: circle with cross = floor drain; triangle = vent; gate valve = bow-tie; check valve = bow-tie with arrow; dashed line = concealed pipe.

Line types: solid thick = visible pipe; dashed = concealed or below slab; centre line = axis of symmetry or pipe centre.

Title block contains project name, drawing number, scale, date, revision, and the designer's name; revisions are clouded and tagged.

Bill of quantities is read from drawings: count fixtures, measure pipe runs by size, and add fittings per junction.

Levels are given in metres above datum (e.g., +2.850); invert levels drop by the pipe gradient along the run.

Quantity take-off: measure pipe by centre-line length per diameter, count fittings and fixtures, and add wastage (typically 5–10% on pipe, 2–5% on fittings).

Rate analysis builds a unit rate from material cost + labour cost + plant + overheads + contractor profit.

Labour constants: a plumber plus helper can install roughly 20–30 m of 15–25 mm GI pipe per day in normal conditions; use published constants for tendering.

Contingency is usually 5–10% of the estimated cost; escalation is added for projects longer than one year.

Bill of quantities (BOQ): item description, unit (m, no., kg), quantity, rate, and amount; measured items must match the drawing.

Cost of a joint includes the fitting, solder/cement, and labour time; a threaded GI joint is costlier in labour than a solvent-welded uPVC joint.

Value engineering: compare life-cycle cost, not just first cost - PPR and CPVC cost more initially but last longer than GI in hard water.

Measurement rules: pipe length is measured along the centre line and does not deduct for fittings under a stated size (commonly below 50 mm).

Leak at a threaded joint: isolate, drain, unscrew, clean threads, apply PTFE tape or jointing compound, and re-tighten; do not over-tighten (cracks the fitting).

Leak at a solvent-welded joint: cut out the fitting and re-make with a coupling; solvent joints cannot be unscrewed.

Pin-hole leak in copper: cut out the damaged section and splice with two couplings, or use a repair clamp for a temporary fix.

Water meter test for hidden leaks: shut all fixtures and watch the meter; a moving dial indicates a leak, often a running cistern or a buried line.

Dye test: add dye to the cistern or trap and check downstream; colour appearing at the wrong place locates a cross-connection or a broken seal.

Acoustic leak detection: listen with a stethoscope or ground microphone at night when background noise is low; hiss = pressure leak, gurgle = drain.

Frozen pipe: thaw with warm air or a hot towel from the open end toward the freeze; never use an open flame on a pressurised line.

Preventive maintenance schedule: inspect traps and vents annually, descale hot-water cylinders, test backflow preventers yearly, and check pump seals.

Every fixture must be trapped and vented; a trap may not be double-trapped or have two fixtures on one trap (except where code allows a combination fixture).

Trap seal depth: 50 mm minimum, 100 mm maximum; deeper seals trap air and drain slowly.

No vertical drop greater than 1.5 m into a trap arm without a vent; the trap arm length is limited (commonly 1.5–2.4 m depending on pipe size).

Water supply pipe may not pass through a sewer or a vent; minimum horizontal separation of 300 mm between water and drain lines, with water above the drain.

Backflow protection is mandatory at any connection to a boiler, irrigation line, or non-potable supply.

Vent terminal must be at least 150 mm above the roof surface and 3 m from an operable window or air intake.

Cleanouts are required at the base of each stack, at changes of direction over 45°, and at intervals not exceeding 15 m in horizontal drains.

Fixtures must be accessible for repair; concealed traps need an access panel.

Lead in drinking water: lead pipes and lead solder are prohibited; test water where lead service lines remain and flush before use.

Legionella risk: hot water should be stored at 60 °C or above and distributed at 50 °C or above; dead legs and lukewarm ranges promote growth.

Asbestos cement pipe: do not cut or abrade dry; wet the material, use respiratory protection, and dispose as hazardous waste.

Noise: supply velocity below 1.5 m/s and drainage stacks with acoustic lagging keep noise within acceptable limits in dwellings.

Waste segregation on site: PVC offcuts, copper, and packaging are separated; solvent cement residues are hazardous waste.

Manual handling: two-person lift for cast iron pipe and cylinders; use a pipe trolley; keep the load close to the body.

Electrical safety: use 110 V site tools or RCD protection; do not work on a pump or immersion heater without isolating and locking off.

First aid for chemical splash: irrigate eyes with clean water for 15 minutes and seek medical help; keep the safety data sheet available.

Pipe cutting: mark square with a square or wrap-around, cut, then file/ream the burr; a square cut is the basis of a leak-free joint.

Threading sequence: cut to length, ream, chamfer, clamp in a vice, oil the die, cut the thread, test-fit the fitting by hand, then tighten with a wrench.

Solvent welding: dry-fit, clean with primer, apply cement to both surfaces, push and twist a quarter turn, hold 30 seconds, and allow full cure before pressure testing.

Soldering copper: clean to bright metal, apply flux, heat the fitting (not the solder), and feed lead-free solder into the joint until a capillary ring forms.

Bending copper: anneal by heating to dull red and cooling, then bend with a spring or bender to avoid flattening the tube.

Pressure test procedure: cap open ends, fill slowly, vent air, pressurise, hold, inspect every joint, then release and record the result.

Level and gradient check: use a spirit level with a wedge or a laser; verify the fall with a straight edge and rule over a known length.

Tool care: wipe pipe wrench teeth, oil the adjusting nut, store dies in oil, and replace a cracked hammer handle - never weld it.