Academic Writing Task 1 · process diagram

The Construction and Operation of a Simple Water Filtration System: IELTS Writing Task 1 sample answer

An IELTS Writing Task 1 process diagram question with a Band 8 sample answer, the chart redrawn with its data, the vocabulary that lifts the report and how to write about process diagrams.
  • 215 words
  • Process diagrams
  • Academic
  • 20 minutes

The question

The diagram below illustrates how a simple water filter is constructed and how it functions to produce clean drinking water.

Summarise the information by selecting and reporting the main features, and make comparisons where relevant. Write at least 150 words.

Water-Filter Assembly
  1. 1.Pouring water into the plastic barrel
  2. 2.Water passes through layers of sand, charcoal, and gravel
  3. 3.Filtered water flows through a pipe into the storage drum
  4. 4.Clean drinking water is collected from the tap

Chart redrawn by BandLadder from the data in the original IELTS practice task. Many IELTS practice tasks come from the Cambridge IELTS series (Cambridge University Press & Assessment); all rights in the original tasks remain with their owners.

Model answer

Band 8 sample answer

Band 8215 words. Every figure in the answer comes from the chart above.

The provided diagram illustrates the construction and operational mechanism of a simple water-filter assembly designed to produce clean drinking water. The system consists of two primary components: a plastic barrel containing filtration media and a separate storage drum for the treated water.

Overall, the process is a gravity-fed system where water is purified by passing through three distinct layers of materials. The assembly is designed to ensure that raw water is effectively filtered before it is transferred to a storage container for later use.

In the first stage, water is poured into the top of the plastic barrel, which is covered by a plastic lid. Inside this barrel, the water must percolate through three sequential layers: sand at the top, followed by charcoal, and finally gravel at the base. These layers act as a physical and chemical filter to remove impurities. Once the water has passed through these materials, it is collected at the bottom of the barrel.

Subsequently, the filtered water is directed through a pipe that connects the base of the filtration barrel to the storage drum. The water enters the storage drum and is held there until needed. Finally, the clean drinking water can be dispensed via a tap located at the bottom of the storage drum into a glass or container.

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Process diagrams

How to write about process diagrams: tips and vocabulary

  • →Say how many stages there are and where the process starts and ends.
  • →Use the passive and sequencers: first, after this, once, finally.
  • →Keep every stage; a missing step costs task achievement.
  • percolate

    to filter gradually through a porous surface or substance

  • sequential

    following a logical order or a particular sequence

  • subsequently

    happening or coming after something else in time

  • impurities

    substances that make something dirty or less pure

  • dispensed

    distributed or provided in portions from a container

  • operational

    relating to the way a machine or system works

Frequently asked questions

What should the overview say?+

The process involves a multi-stage filtration system where water is purified through layers of natural materials before being stored for consumption.

How many words and how long for IELTS Writing Task 1?+

At least 150 words; 170 to 200 is the safe range. Spend about 20 minutes on it and leave 40 for Task 2, which carries twice the marks.

How is IELTS Writing Task 1 scored?+

On four criteria: task achievement, coherence and cohesion, vocabulary, and grammatical range and accuracy. A clear overview of the main features is what most separates Band 6 from Band 7 and above.

How do I describe process diagrams?+

Say how many stages there are and where the process starts and ends. Use the passive and sequencers: first, after this, once, finally. Keep every stage; a missing step costs task achievement.

Keep practising

More process diagrams

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