--- title: "Principles of laying out water supply system" subject: "Building Technology" chapter: 12 key: "semester_6/building_technology:water-supply-principles" source: https://www.bctengineer.com/q/semester_6/building_technology/water-supply-principles site: BCT Engineering --- # Principles of laying out water supply system Building Technology · Chapter 12: Other services in building - Asked in: 2077 Chaitra, 3 marks - Video: [How to Design Water Supply System - Part I](https://www.youtube.com/watch?v=FBu_DU-hK04) — Phil 4 Science - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/water-supply-principles - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-12 ## Question List out the principles to be followed while laying out the water supply system in building. ## Short answer Provide adequate pressure (3–5 m residual head) at every fixture, use short direct pipes with few bends, storage tanks at sufficient height, isolation valves on branches, and keep water pipes separate from drains. Avoid contamination, protect pipes, ensure accessibility, use non-toxic materials, group fixtures around stacks, and separate hot and cold lines. ## Answer Principles for laying out the water supply system in a building: 1. **Adequate quantity and pressure** at every fixture (minimum residual head about 3-5 m); size the pipes for peak demand. 2. **Short, direct pipes** with few bends and fittings, to reduce friction loss and cost. 3. **Storage:** sump and overhead tank sized for the demand; the tank placed high enough to give sufficient head at the top floor. 4. **Valves:** a gate valve at each branch and fixture so that parts can be isolated; air valves at high points and drain valves at low points. 5. **Avoid contamination:** keep water pipes separate from drains and never in contact with sewers; keep tanks covered; where pipes cross a sewer, lay them at least 0.5 m above it. 6. **Protection:** pipes in ducts or chases, lagged in cold places, not embedded under foundations or in columns; allowance for expansion. 7. **Accessibility** for repair; joints exposed or in inspection ducts. 8. **Material:** non-toxic, durable pipes (GI, HDPE, PVC, CPVC). 9. **Grouping of fixtures** around vertical shafts (kitchens and toilets stacked) for economy. 10. **Hot and cold supply** kept separate, with insulation on hot pipes. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What should the layout ensure at every fixture? A. Adequate quantity and pressure, with minimum residual head about 3-5 m, pipes sized for peak demand B. Average demand only, no residual head C. Maximum pressure whatever the pipe D. Pipes sized for minimum demand Answer: A. Pipes are sized for peak demand so each fixture gets enough quantity and a residual head of about 3-5 m. (Key point: Quantity and pressure) 2. How is contamination of the water supply avoided? A. Lay water pipes touching sewers B. Keep water pipes separate from drains, never in contact with sewers, tanks covered, and pipes at least 0.5 m above a crossing sewer C. Leave tanks uncovered for ventilation D. Lay water pipes below sewers in the same trench Answer: B. Water pipes are kept apart from drains and above sewers (at least 0.5 m) and tanks are covered. (Key point: Avoid contamination) 3. Why are valves fitted at each branch and fixture, and air and drain valves at high and low points? A. To increase friction B. To isolate parts for repair, release air at high points and drain at low points C. To reduce the head D. To store water Answer: B. Gate valves isolate sections, air valves release trapped air at high points, and drain valves empty low points. (Key point: Valves) 4. Why should pipes be short and direct with few bends? A. To reduce friction loss and cost B. To increase pressure loss C. To make repairs harder D. To raise the tank height Answer: A. Fewer bends and shorter runs reduce friction loss and material cost. (Key point: Short direct pipes) ## Related in Building Technology - [Short note: Water supply and distribution system](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-distribution-short) — Building Technology, chapter 12, asked 2× - [Earthquake protection and resistant building principles](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aeq-protection-principles) — Building Technology, chapter 11, asked 3× - [Setting out of a building](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asetting-out-building) — Building Technology, chapter 2 - [Water supply and sanitation management](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-supply-sanitation) — Building Technology, chapter 12 - [Domestic water supply and drainage systems](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-supply-drainage) — Building Technology, chapter 12 - [Domestic water supply; septic tank and soak pit](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-supply-septic-067as) — Building Technology, chapter 12 ## Related in other subjects - [Criteria for designing and laying out tunnels](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydraulic-tunnel-design-layout) — Hydro Power, chapter 5, asked 2× - [Transition deflection angle derivation and laying out](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atransition-deflection-angle-derive-laying-out) — Surveying II, chapter 6 - [Typical water supply system and components](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Atypical-ws-system-components) — Water Supply Engineering, chapter 1, asked 4× - [Water supply system and historical development](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aws-historical-development) — Water Supply Engineering, chapter 1