CTVET Ghana Certificate II - Plumbing flashcards

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

Hierarchy of control

The order for reducing risk: eliminate the hazard, substitute it, use engineering controls, then administrative controls, and finally PPE as the last line of defence.

Confined space entry

Entry into a manhole, tank, or pit requires a permit, atmospheric testing for oxygen and toxic gas, forced ventilation, a standby person, and a retrieval harness.

Ladder 4:1 rule

Set a ladder so the base is one metre out for every four metres of height, keep three points of contact, and extend the top about one metre above the landing.

First-angle projection

A drawing convention where each view is placed on the far side of the object, so the plan appears below the front elevation.

Gradient fall formula

Fall equals length multiplied by gradient. A six-metre run at 1:60 gives a fall of 100 millimetres between its two ends.

Nominal bore (DN)

The approximate internal diameter used to designate pipe size. Outside diameter governs fitting choice for plastics such as 20 mm PPR or 110 mm PVC soil.

Valve selection rule

Gate or ball valves isolate flow fully, globe valves throttle flow, check valves allow one-way flow, and air admittance valves vent drains.

Minimum copper bend radius

Cold-bending copper below about three to four times the outside diameter flattens or kinks the pipe, so use a bender or anneal the copper first.

Solvent weld sequence

Cut square, chamfer, clean, apply primer, apply cement to both surfaces, push fully home with a quarter turn, hold thirty seconds, and cure before testing.

Indirect cold water system

Mains water fills a storage cistern, which then feeds the cold distribution and the hot water cylinder, giving a reserve when mains supply is interrupted.

Static head to pressure

Pressure in bar equals head in metres multiplied by 0.0981. A ten-metre head gives about one bar at the outlet before friction losses.

Trap seal depth

A trap should hold a water seal of 50 to 75 millimetres. Less risks evaporation and gassing off; more risks self-siphonage.

Self-cleansing velocity

A drain gradient that keeps flow at about 0.7 metres per second, commonly 1:40 to 1:60 for small waste and 1:60 to 1:80 for soil.

WC pan set-out

The soil pipe centre is typically 200 to 300 millimetres from the finished wall. Check the pan's own dimension before fitting the connector.

Appliance trap upstand

A washing machine or dishwasher hose should discharge into a standpipe with a minimum 600 millimetre upstand, hooked above the trap weir to prevent backflow.

Compression joint leak

First tighten the nut a quarter turn. If it still leaks, cut out and remake the joint with a new olive rather than adding more tape.

Water hammer remedy

Secure loose pipe clips, fit a shock arrester or check valve, check the pressure-reducing valve setting, and upsize the pipe to reduce velocity.

Price from margin

When profit is stated as a margin, price equals cost divided by one minus the margin. A 20 percent margin on 100 cost gives a price of 125.

Quote versus estimate

A quotation is a fixed offer to do the work at a stated price. An estimate is approximate and must be labelled as such to avoid disputes.

Scope of competence

Work only within the training and registration you hold, and refer work such as gas or electrical connections outside your certificate to a qualified person.

Written confirmation

Confirm verbal instructions in a job sheet or message, keep a copy, and record any agreed change with its price and time impact.

Risk assessment steps

Identify the hazard, decide who may be harmed and how, rate the risk, record the controls, and review when the work or conditions change.

Isolation procedure

Identify the supply, switch off, lock off, attach a tag, then prove dead with a tester checked before and after use.

Bend developed length

For a ninety-degree bend, the developed length along the centre line is approximately 1.57 multiplied by the bend radius.

Thermal expansion

Expansion equals coefficient times length times temperature rise. uPVC expands about 0.07 millimetres per metre for each degree Celsius.

Dielectric union

A fitting placed between dissimilar metals, such as copper and galvanised steel, to break the electrical path and prevent galvanic corrosion.

Pressure test value

Test domestic cold pipework at 1.5 times working pressure, commonly 10 bar where rated, and hold it for at least one hour with no drop.

Drain air test

Seal the drain section and apply air at about 38 millimetres water gauge for three minutes, or use a water test with a 1.5 metre head.

Inspection chamber rule

Fit an inspection chamber at every junction, at every change of direction, and at intervals of about 45 metres on straight drain runs.

Cistern fill setting

Set the float valve so water sits about 12 millimetres below the overflow line, and fit a double-check valve or air gap to prevent backflow.

Relief valve discharge

A water heater pressure relief valve must discharge to a safe place and must never be capped or plugged, and it should be tested annually.

Break-even point

Fixed costs divided by the difference between price per job and variable cost per job gives the number of jobs needed to cover costs.

Markup versus margin

A 25 percent markup on cost equals a 20 percent margin on price. State which one the quotation uses so the client can compare.