IELTS · Guide 15 · 9 min read

IELTS Writing Task 1 sample answers: process diagram on rainwater harvesting

An IELTS Academic Task 1 process on rainwater reuse at a school, described in words, with answers at bands 8, 6.5 and 5 and commentary.

How to use this worked session

This page takes one Academic Task 1 process and shows three answers at different levels, with comments on what lifted or limited each one. Instead of a picture, the diagram is described stage by stage below. Write your own answer first in 20 minutes, aiming for at least 150 words, then compare.

The task

You should spend about 20 minutes on this task.

The diagram shows how rainwater is collected from the roof of a school building and treated so that it can be used again.

Summarise the main features of the diagram, and make comparisons where relevant.

Write at least 150 words.

What the diagram shows

The diagram is a cross-section of a two-storey school. Arrows link eight labelled stages:

1. Rain falls on the sloping roof and runs into gutters along the edges.
2. A leaf screen at the top of each downpipe catches leaves and twigs.
3. The first few litres of each shower, which carry most of the roof dust, are sent into a small first-flush chamber and drained away.
4. The remaining water flows into an underground storage tank that holds 10,000 litres.
5. When the tank is full, extra water leaves through an overflow pipe into a soakaway under the playing field.
6. An electric pump lifts water from the tank through a fine filter.
7. The filtered water passes under an ultraviolet (UV) lamp, which kills bacteria.
8. The treated water is held in a header tank in the roof space and supplies the toilets and the school garden.

The process is invented for practice.

What to notice before you write

• It is a man-made process with a clear start (rain on the roof) and end (water used in toilets and the garden).
• It falls into two halves: collection and storage (stages 1 to 5) and treatment and supply (stages 6 to 8).
• There is one side route: overflow water leaves the system at stage 5.

Strong response (around band 8)

The diagram illustrates the way in which rain falling on a school roof is captured, cleaned and stored so that it can be reused within the building and its grounds. Overall, the system involves eight stages, beginning with collection from the roof and ending with treated water being supplied to the toilets and the garden. The process combines simple mechanical screening at the start with pumping and disinfection towards the end. To begin with, rainwater runs off the sloping roof into gutters and passes through a screen at the top of each downpipe, where leaves and twigs are caught. The first portion of each shower, which contains most of the dust from the roof, is then diverted into a separate chamber and drained away. The cleaner water that follows is channelled into an underground tank with a capacity of 10,000 litres; any surplus, once this is full, escapes through an overflow pipe into a soakaway beneath the playing field. In the second half of the process, water is drawn from the tank by an electric pump and forced through a fine filter. It is then exposed to ultraviolet light, which destroys bacteria, before being held in a header tank in the roof space. From there, it is used to flush the toilets and to water the school garden.

Commentary

• Task Achievement: Every stage is covered accurately, including the first-flush chamber and the overflow route, which weaker answers often miss. The overview gives the start and end points and, usefully, describes the nature of the process (screening first, treatment later). Nothing is added that the diagram does not show.
• Coherence and Cohesion: The two body paragraphs follow the two halves of the process, which makes the structure easy to see. Sequencing is varied ("To begin with", "then", "that follows", "once this is full", "before being", "From there") rather than a list of "First ... Then ... Next".
• Lexical Resource: The answer paraphrases the labels instead of copying them ("caught" for "catches", "diverted" for "sent", "a capacity of 10,000 litres", "exposed to ultraviolet light"). Process words such as "channelled", "surplus" and "disinfection" are precise.
• Grammatical Range and Accuracy: The passive is used where the actor does not matter ("is diverted", "is drawn", "is used"), mixed with active verbs for natural movement ("runs off", "escapes"). Relative clauses and "before being held" add range. No noticeable errors.

What kept it from the top band: a brief comparison, for example that only the water used indoors and in the garden is treated while the overflow is not, would have used the "make comparisons" part of the task more fully.

Pass-level response (around band 6.5)

The diagram shows how a school collects rainwater and makes it clean, so it can be used again. Overall, there are eight steps in the process, from rain falling on the roof to the water being used for toilets and the garden. First, the rain falls on the roof and goes into the gutters. Then it goes down the pipes, and there is a screen which stops leaves and sticks. After that, the first water from the rain is dirty because of the dust, so it is sent to a small chamber and removed. Next, the rest of the water goes into a big tank under the ground, which can hold 10,000 litres. If the tank becomes full, the extra water goes out through a pipe into the playing field. In the next stage, a pump takes the water from the tank and push it through a filter. After this, a UV lamp kill the bacteria in the water. Finally, the clean water is kept in a tank in the roof and it is used for flushing toilets and watering the garden.

Commentary

• Task Achievement: All the main stages are included and the overview gives the start and end points. The overview is thin, though: "eight steps" does not tell the reader anything about the kind of process. The answer is just over the word limit, and a few details are slightly inaccurate ("goes down the pipes" before reaching the screen; the overflow goes to a soakaway, not simply "into the playing field").
• Coherence and Cohesion: The sequence is clear and the two-paragraph split matches the two halves of the process. Sequencing words are correct but predictable: "First", "Then", "After that", "Next", "In the next stage", "After this", "Finally".
• Lexical Resource: Mostly simple and clear vocabulary ("goes into", "big tank", "takes the water"), with "goes" used five times. Some paraphrasing of the labels is attempted ("sticks" for "twigs").
• Grammatical Range and Accuracy: A mix of active and passive forms, with a correct conditional ("If the tank becomes full"). Agreement errors appear in the second body paragraph ("a pump takes ... and push", "a UV lamp kill").

What would lift it: describe the process in the overview (collection and storage, then treatment), use more passives for the treatment stages, and vary the verbs of movement.

Weaker response (around band 5)

The diagram is about the rainwater in the school. I think this is very good idea because water is very important and we must save the water. First the rain is fall on the roof and run into gutters along the edges. Then the leaf screen remove the leaves and twigs. After the water is go into the tank under the ground. The tank is very big, it is 10,000 litres. Then there is a pump. The pump is electric and it take the water from the tank. Then the water go through a filter and then the UV lamp. The UV lamp is for the bacteria. Then the water go to other tank in the roof. At the end the school use the water for toilets and garden. In this way the school save money and also help the environment. Other schools also must to do this system. In conclusion the process have many steps and it is very useful.

Commentary

• Task Achievement: The answer follows the basic route, but it leaves out two stages: the first-flush chamber and the overflow. There is no real overview. Instead, the opening and closing paragraphs give the writer's opinion ("very good idea", "very useful", "other schools must do this"), which the task does not ask for. The answer is around the minimum length only because of these comments.
• Coherence and Cohesion: The order of stages is correct, but "Then" begins four sentences, and the final paragraphs drift into commentary rather than description.
• Lexical Resource: Limited range, with phrases copied from the labels ("run into gutters along the edges", "leaves and twigs"). Copied wording does not show the writer's own vocabulary. "The UV lamp is for the bacteria" is too vague to explain what happens.
• Grammatical Range and Accuracy: The writer attempts the passive but forms it wrongly ("the rain is fall", "the water is go"). Agreement errors are frequent ("the leaf screen remove", "the school use", "the process have"), and "must to do" is incorrect.

What would lift it: remove all opinions, write a one-sentence overview of the start, end and main phases, include every stage, and learn the passive form (is + past participle: "is collected", "is pumped").

The three answers side by side

Self-check checklist

1. Does my overview say where the process starts, where it ends and what its main phases are?
2. Have I included every stage, including any side routes such as overflow?
3. Have I used my own words rather than copying the labels?
4. Did I use the passive where the person doing the action is not important?
5. Are my sequencing words varied, and do they show the real order?
6. Have I kept my opinion out of the answer?
7. Does each sentence have a correct subject and verb ("the water is pumped", not "the water is go")?
8. Is my answer at least 150 words?

About the band levels

The band levels on this page are our own estimates for practice purposes. They are not official scores and are not produced or endorsed by any IELTS partner. Only a certified examiner marking a real test can give you an official band.

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• IELTS Writing Task 1 Academic: charts, graphs, processes and maps
• IELTS Writing band descriptors explained in plain words
• Back to the IELTS hub