---
title: "Methods of distribution of water"
subject: "Water Supply Engineering"
chapter: 7
key: "semester_5/water_supply_engineering:methods-of-distribution"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/methods-of-distribution
site: BCT Engineering
---

# Methods of distribution of water

Water Supply Engineering · Chapter 7: Reservoirs and Distribution System

- Asked in: 2068 Chaitra, 8 marks
- Video: [Water Distribution Methods. Public Health Engineering. Gravity Method, pumping Method. Civil engg.](https://www.youtube.com/watch?v=fRHn4NmXfUg) — AboutCivil Engineer's
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/methods-of-distribution
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-7

## Question

Describe, with their respective merit and demerit, the various methods of distribution of water.

## Short answer

Gravity system uses elevation for flow, economical but requires high source. Pumping uses pumps directly, high pressure but costly. Combined system pumps to reservoir for gravity distribution, most practical.

## Answer

Water is delivered from the service reservoir to the consumers by one of three methods, depending on the position of the source and the ground levels.

#### 1. Gravity system
The source or the service reservoir is at a level high enough above the town, so that water flows by gravity at the required pressure.

```text
 Source/Reservoir
   \
     \  gravity flow
       \_______ town
```
- **Merits:** most economical and reliable, since there is no pumping and no power cost; simple to operate; very low maintenance; pressure is steady.
- **Demerits:** possible only where a high source exists; pressure at low ground may be too high so BPT or PRV are needed; large initial pipe cost for long transmission lines.

#### 2. Pumping system (direct pumping)
Treated water is pumped directly into the mains without any storage; the pumps run according to the demand.
- **Merits:** high pressure can be achieved easily, useful for fire fighting; the reservoir cost is saved; suited for flat towns.
- **Demerits:** pumps must run all the time with varying load, so the cost is high and efficiency is low; any breakdown or power failure stops the supply; standby pumps are needed; pressure fluctuates with the demand.

#### 3. Combined (dual) system - pumping with storage
Pumps lift water at a uniform rate into an elevated service reservoir, which supplies the town by gravity and also receives the excess flow in the low-demand hours.

```text
 Source -> Pump -> [Elevated reservoir] -> distribution
                        |  (surplus stored in the off-peak hours)
```
- **Merits:** the pumps work at a constant, efficient rate; the supply continues for a time even if the pump fails; peak demands and fire are met from storage; the pump size and the running cost are less. This is the most common system.
- **Demerits:** needs the cost of the reservoir and also of the pumps and power; more complex operation and maintenance.

#### Choice
The gravity system is preferred where the topography allows; the combined system is the most practical in flat towns; direct pumping is used only for small schemes or as a temporary arrangement.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the main merit of the gravity system?
   A. High pressure for fire fighting by pumps
   B. Most economical and reliable, with no pumping or power cost
   C. Needs standby pumps
   D. Saves the reservoir cost
   Answer: B. No pumping means low cost, simple operation and steady pressure. (Key point: Gravity system)

2. What is a demerit of direct pumping without storage?
   A. Pressure cannot be high
   B. Any pump breakdown or power failure stops the supply
   C. It needs an elevated tank
   D. It is cheapest to run
   Answer: B. No storage, so supply depends entirely on the pumps; they also run at varying load. (Key point: Direct pumping)

3. Why do pumps work efficiently in the combined system?
   A. They run at a uniform rate, storing surplus in the elevated reservoir
   B. They run only at peak hours
   C. They run without a reservoir
   D. They are replaced by gravity
   Answer: A. Constant-rate pumping with storage handles demand variation and the supply continues if a pump fails. (Key point: Combined system)

4. Which method is the most common and practical for flat towns?
   A. Gravity
   B. Direct pumping
   C. Combined (pumping with storage)
   D. Radial gravity only
   Answer: C. Without high ground, pumping with an elevated reservoir is the usual choice. (Key point: Choice of method)

## Related in Water Supply Engineering

- [Distribution layouts, merits and demerits](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-layouts-merits-demerits) — Water Supply Engineering, chapter 7, asked 6×
- [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×
- [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×
- [Distribution layout for haphazardly growing city](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Alayout-haphazard-city) — Water Supply Engineering, chapter 7, asked 2×
- [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
- [Dead end distribution system](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adead-end-system) — Water Supply Engineering, chapter 7

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