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

Construction and function of a simple water filter - IELTS Writing Task 1

You should spend about 20 minutes on this task.

Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

Write at least 150 words.

A student's answer to this task, and the feedback on it

Written by an IELTSX user under exam conditions and published unedited and anonymously. Band 7.5 · 163 words.

The diagram illustrates the structure of a simple water filter and explains how it works to produce clean water.

Overall, the filter has a simple design consisting of several layers of different materials. As water passes through these layers, dirt and other impurities are removed before the clean water is collected at the bottom.

At the top of the filter, dirty water is poured into a container. It then flows down through a number of filtering materials. The first layer is made of small stones or gravel, which remove large pieces of dirt. Below this is a layer of sand that filters out smaller particles. Finally, the water passes through charcoal, which helps remove very fine impurities and improves the quality of the water.

After passing through all the layers, the filtered water reaches the bottom of the container, where it is collected for use. The process does not require electricity and relies only on gravity to move the water through the filter

Examiner feedback

This is a very strong response that clearly and accurately describes the process shown in the diagram. The organization is logical, and the grammar is highly controlled; to reach a higher band in Lexical Resource, the student should aim for more sophisticated, technical vocabulary related to filtration and mechanics.

Task Achievement - 8

- The response covers all key stages of the diagram including the input, the specific filtration layers, and the output. - A clear overview is provided in the second paragraph, identifying the main purpose and design. - Data/features are appropriately selected, though the description of the container itself could be slightly more detailed.

Coherence & Cohesion - 8

- The response is logically organized following the physical path of the water from top to bottom. - Transition signals such as "At the top," "Below this," and "Finally" create a smooth progression. - Paragraphing is used effectively to separate the overview from the detailed process description.

Lexical Resource - 7

- Vocabulary is accurate and appropriate (e.g., "impurities," "charcoal," "collected"). - While the range is sufficient for the task, it relies on somewhat basic terminology where more technical vocabulary could have been used (e.g., "sediment" instead of "pieces of dirt"). - Spelling and word formation are entirely correct.

Grammatical Range & Accuracy - 8

- A good variety of complex structures is used, particularly relative clauses and passive voice, which are appropriate for process descriptions. - The majority of sentences are error-free and punctuation is handled with precision. - Effective use of present simple tense to describe a universal process.

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