---
title: "Continuous vs intermittent supply"
subject: "Water Supply Engineering"
chapter: 7
key: "semester_5/water_supply_engineering:continuous-vs-intermittent"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/continuous-vs-intermittent
site: BCT Engineering
---

# Continuous vs intermittent supply

Water Supply Engineering · Chapter 7: Reservoirs and Distribution System

- Asked in: 2071 Chaitra, 8 marks; 2069 Asar, 6 marks; 2076 Chaitra, 2 marks; 2075 Asoj, 2 marks; 2068 Baisakh (old course), 4 marks (asked 5 times)
- Video: [Distribution reservoir, Continuous and intermittent system of water supply- Environmental](https://www.youtube.com/watch?v=8NWgtJBSk34) — Study Civil Engineering with Shuja Askari
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/continuous-vs-intermittent
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-7

## Question

Differentiate/compare the continuous and intermittent systems of water supply with their merits and demerits.

## Short answer

Continuous system supplies water 24 hours, ensuring safe quality, fire readiness, and smaller pipes but higher leakage and treatment cost. Intermittent system supplies few hours daily, reducing water use but risking contamination, requiring larger pipes and household storage, and causing pressure fluctuations and pipe damage. Continuous is preferred for safety; intermittent used where water is scarce.

## Answer

In the **continuous system** water is available in the pipes for all 24 hours of the day, while in the **intermittent system** water is supplied only for fixed hours (for example 2–4 hours in the morning and evening) and the pipes are empty or shut for the rest of the day.

| Basis | Continuous system | Intermittent system |
|---|---|---|
| Supply hours | 24 hours | A few hours per day |
| Water quality | Pipes always full and under pressure, so no entry of dirty water | Empty pipes may suck in polluted water when the supply is off; risk of contamination |
| Storage in houses | Not needed | Households must store water in tanks and containers |
| Pipe sizes | Smaller, as demand is spread out | Larger, as the whole day's demand is supplied in a short time |
| Wastage | Higher if taps are left open; leakage continues all day | Less wastage by consumers |
| Fire fighting | Water is always available at hydrants | Hydrants have no water when the supply is off |
| Pressure | Steady and more uniform | Fluctuates; high at the start of the supply |
| Operation of pumps | Continuous, constant load | Simple, but heavy load during supply hours |
| Cost | Larger source and more treated water needed | Less water needed, but larger pipes and household storage add to the cost |

#### Merits of the continuous system
1. Safe, because positive pressure always prevents contamination.
2. Water is available for fire fighting at any time.
3. Consumers get water at any hour, without household storage.
4. Smaller pipe sizes are enough.

#### Demerits of the continuous system
1. Wastage and leakage can be heavy, so a larger source and metering are needed.
2. Needs a larger quantity of water and a higher cost of treatment.
3. Burst pipes cause large losses before they are detected.

#### Merits of the intermittent system
1. Less water is wasted, so a smaller source is enough.
2. Needs less treated water, so it suits places where the source is scarce.

#### Demerits of the intermittent system
1. Contamination risk during empty periods; poor water quality.
2. Large pipes, valves and fittings are needed to deliver the daily demand in a few hours.
3. Consumers must store water; no water at hydrants during the off period.
4. Frequent wetting and drying of pipes causes corrosion and damage; air in the pipes gives false meter readings.

## Check yourself

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

1. How do the systems differ?
   A. Continuous supplies 24 h; intermittent supplies fixed hours
   B. Continuous supplies 4 h
   C. Both supply 24 h
   D. Intermittent has no pipes
   Answer: A. The key difference is hours of supply. (Key point: Definition)

2. Why is the intermittent system less safe?
   A. Pressure is too high
   B. Empty pipes can suck in polluted water when supply is off
   C. It uses chlorine
   D. Pipes are too small
   Answer: B. Positive pressure of the continuous system prevents ingress. (Key point: Contamination)

3. Which system needs larger pipes?
   A. Continuous
   B. Neither
   C. Intermittent, to deliver the day's demand in a few hours
   D. Both equally
   Answer: C. Compressed supply hours raise peak flow. (Key point: Pipe size)

4. Which is a demerit of the continuous system?
   A. No fire flow
   B. Pollution entry
   C. Needs household storage
   D. Greater wastage and leakage, needing a larger source
   Answer: D. Taps left open and leaks run all day. (Key point: Wastage)

## Related in Water Supply Engineering

- [Planning of distribution; intermittent supply](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-planning-intermittent) — Water Supply Engineering, chapter 7
- [Balancing reservoir, intermittent supply 7-10 and 17-20](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ares-c74) — Water Supply Engineering, chapter 7
- [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×
- [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×
- [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×
- [Protection and maintenance of water supply](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aws-maintenance-types) — Water Supply Engineering, chapter 7, asked 4×

## Related in other subjects

- [Intermittent vs continuous flushing basin](https://www.bctengineer.com/question.md?key=semester_7%2Fhydropower_engineering%3Asettling-basin-intermittent-vs-continuous-5cumec) — Hydropower Engineering, chapter 5
- [Forward vs reverse engineering merits and demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fobject_oriented_analysis_and_design%3Aforward-reverse-engineering-merits) — Object Oriented Analysis and Design, chapter 4, asked 3×
- [Merits and demerits of active vs passive filters](https://www.bctengineer.com/question.md?key=semester_5%2Ffilter_design%3Aactive-passive-merits-demerits) — Filter Design, chapter 6
- [Merits and demerits of flat-top sampling](https://www.bctengineer.com/question.md?key=semester_6%2Fcommunication_systems%3Aflat-top-sampling-merits) — Communication Systems, chapter 4