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Level 2 · Plumbing revision

Cold Water Systems revision notes

Direct and stored supplies, cistern storage, float-operated valves and protecting the supply from backflow.

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  • 16notes, free to read
  • 103questions; 25 free to try
  • 7topics

G1: Cold Water Supply & Service Pipes

  1. Cold water sources and water hardnessWhere UK mains water comes from, why chalk and limestone make it hard, how hardness is measured, and how softeners and scale reducers are fitted.
  2. Underground water and gas pipes: depth and which is whichLay a water service pipe 750–1350 mm deep with a sealed, ducted entry, and recognise a buried gas service: usually yellow, 375 mm or more down.
  3. What Approved Document G coversA plain-English tour of the areas Part G of the Building Regulations guides, from cold water to scald safety.

C&G Unit 204: Cistern Storage & Float Valves

  1. Direct and indirect cold water systemsDirect against indirect cold water: mains-fed or cistern-fed outlets, gravity pressure of about 0.1 bar per metre of head, and the trade-offs of each.
  2. Sizing a cold water storage cistern (worked example)A method for turning occupancy and a per-person allowance into a cistern capacity, with the arithmetic shown.
  3. Unit 204: Cold water storage and float valvesStored-water protection, inlet control and safe warning/overflow arrangements.

G2: Water Efficiency & Hot Water Safety

  1. Part G water efficiency and bath hot-water limitsThe Part G water-use limit for new dwellings, why fittings drive it, why saving hot water saves twice, and the 48 °C bath limit.

C&G Unit 204: Pipe Materials, Isolation & Frost Protection

  1. Cold pipe materials and frost protectionCommon cold-water pipe materials, isolation, and why and where cold pipework must be protected from freezing.
  2. Isolation valves and the water supply boundaryThe different shut-off valves in a cold water system, and where the water company's pipework ends and yours begins.
  3. Water content of a pipe run (worked example)A worked calculation of how much water a length of pipe holds, useful for filling, flushing and dosing.
  4. Water hammer: causes and curesWhy pipes bang when a valve shuts fast, and the practical ways to stop it.

C&G Unit 204: Backflow Prevention & Contamination Risk

  1. Backflow prevention: hoses, pressure and air gapsTrace how contaminated water could travel backwards, then choose protection for the actual risk.

C&G Unit 204: Stagnation, Storage Turnover & Legionella Basics

  1. Decommissioning and recommissioning water and heating systemsHow to isolate, drain, disconnect and cap cold, hot and heating systems, remove dead legs, protect empty homes from frost and recommission safely.
  2. Flushing and disinfecting a new cold water systemThe hygiene steps that leave a new or repaired cold water system clean before use.Checklist
  3. Stagnation, temperature and Legionella riskWhy warm, still water breeds bacteria, and the everyday habits that keep a cold water system safe.

Water Efficiency & Sustainability: Saving, Rainwater & Greywater

  1. Water efficiency, greywater and rainwaterReduce use without spoiling function, and keep reused water separate from the wholesome supply.

Turn cold water theory into a system you can explain

Sketch a direct supply and a stored supply, then follow the route to an outlet. Use the notes to explain cistern components, isolation, pressure and contamination risks. In a plumbing test, check which system the question describes before applying its rule.

Try the free cold-water questions after a topic, or work through a head-to-pressure calculation for a cistern-fed outlet. For the wider Level 2 plumbing revision plan, compare your course topics with the plumbing study hub.

More Plumbing modules

Every module has its own revision notes and question bank.

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