--- title: "Distribution layouts, merits and demerits" subject: "Water Supply Engineering" chapter: 7 key: "semester_5/water_supply_engineering:distribution-layouts-merits-demerits" source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/distribution-layouts-merits-demerits site: BCT Engineering --- # Distribution layouts, merits and demerits Water Supply Engineering · Chapter 7: Reservoirs and Distribution System - Asked in: 2079 Bhadra, 2+6 marks; 2080 Baisakh, 6+2 marks; 2073 Chaitra, 4 marks; 2075 Asoj, 8 marks; 2071 Shrawan, 6 marks; 2066 Jestha (old course) (asked 6 times) - Video: [WATER DISTRIBUTION SYSTEM LAYOUTS, PART 26, ENVIRONMENTAL ENGINEERING](https://www.youtube.com/watch?v=OALV4uxF7e8) — Vidhya Focus-2020 - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/distribution-layouts-merits-demerits - Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-7 ## Question List/describe the various types of layouts of the water distribution system with their merits and demerits (and explain why different types of layouts are suggested). ## Short answer Four main layouts: dead end (tree) for irregular towns, simple but causes stagnation; grid iron for planned towns, good pressure and fire flow but costly; circular (ring) for well-planned towns, dual supply but expensive; radial for zoned towns with central reservoirs, high pressure but needs many reservoirs. Choice depends on town pattern, topography, cost and reliability. ## Answer Layout means the arrangement of mains, sub-mains and branches in a distribution system. The four common types are dead end, grid iron, circular (ring) and radial. The best layout depends on the road pattern, topography and size of the town, so different layouts are recommended for different places. #### 1. Dead end (tree) system ```text R ====+====+====+==== Branches end at dead ends | | | ``` - **Merits:** simple design; low cost (less pipe and fewer valves); suited to irregular towns; discharge in each pipe is known. - **Demerits:** stagnation at dead ends; the whole area beyond a break loses water; poor pressure at the ends; limited fire flow. #### 2. Grid iron (reticulation) system ```text R ==+====+====+== | | | --+----+----+-- interconnected grid | | | ``` - **Merits:** water circulates, with no dead ends; supply continues during repair; uniform pressure; good fire flow. - **Demerits:** difficult design (Hardy-Cross); high cost (more pipes and valves); needs skilled maintenance. #### 3. Circular (ring) system ```text +------------+ | Main ring | R ===+--+----+----+ inner sub-mains | | | | +------------+ ``` - A closed ring main runs round the town, with sub-mains inside it. Suited to well planned towns with a circular or square pattern. - **Merits:** each point can be fed from two directions, so supply continues during repair; good pressure and fire flow. - **Demerits:** more pipe length and valves; costly; difficult design. #### 4. Radial system ```text \ | / \ | / ----( R )---- water flows outwards / | \ / | \ ``` - The town is divided into zones. Each zone has a service reservoir at its centre, and pipes radiate outwards from it along the roads. - **Merits:** quick supply and high pressure; simple design; small pipe sizes. - **Demerits:** many reservoirs are needed; higher cost; works only for towns planned on a radial pattern. #### Why different layouts? A town may be planned and regular (grid iron or ring), haphazardly grown or hilly (dead end), or large with several zones (radial). Cost, reliability, pressure and ease of maintenance have to be balanced against each other, so no single layout suits every town. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the main demerit of the dead end system? A. High cost B. Needs Hardy-Cross design C. Stagnation at dead ends and loss of supply beyond a break D. Too many reservoirs Answer: C. Water does not circulate at the ends and one break cuts off everything beyond it. (Key point: Dead end) 2. Which feature is a merit of the grid iron system? A. Water circulates with no dead ends, so supply continues during repairs B. Simplest design C. Lowest cost D. Uses fewest valves Answer: A. Interconnected pipes allow multiple paths. (Key point: Grid iron) 3. What is typical of the radial system? A. One ring main only B. Reservoir at centre with pipes radiating outwards; zones fed by separate reservoirs C. Pipes end blind D. No reservoir Answer: B. It gives quick, high-pressure supply but needs many reservoirs. (Key point: Radial) 4. Why are different layouts recommended? A. One layout is always best B. Only law decides C. Only pipe material matters D. Road pattern, topography and size vary and cost, reliability and pressure must be balanced Answer: D. No single layout suits every town. (Key point: Why different layouts) ## Related in Water Supply Engineering - [Distribution layouts, pros/cons, improvements](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-layouts-improvements) — Water Supply Engineering, chapter 7, asked 4× - [Three pipe materials with merits/demerits](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apipe-materials-merits-demerits) — Water Supply Engineering, chapter 8, asked 4× - [Dead end distribution system](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adead-end-system) — Water Supply Engineering, chapter 7 - [Design steps and criteria of distribution system](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-design-steps) — Water Supply Engineering, chapter 7, asked 3× - [Methods of distribution of water](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Amethods-of-distribution) — Water Supply Engineering, chapter 7 - [Grid iron system of distribution](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Agrid-iron-system) — Water Supply Engineering, chapter 7 ## Related in other subjects - [Merits and demerits of grid connected system](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Agrid-connected-merits-demerits) — Transmission and Distribution System Design, chapter 1 - [Merits and demerits of interconnected system](https://www.bctengineer.com/question.md?key=semester_5%2Fpower_system_analysis_ii%3Ainterconnection-merits-demerits) — Power System Analysis II, chapter 1, asked 3× - [Verify suggested discharge distribution (Hardy Cross)](https://www.bctengineer.com/question.md?key=semester_4%2Fhydraulics%3Ahardy-cross-verify-suggested-distribution) — Hydraulics, chapter 3 - [Merits and demerits of DC track electrification](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Adc-track-electrification-merits) — Utilization of Electrical Energy, chapter 4