The diagram below shows how a central heating system in a house works.
Sample Response
The given diagram shows how a central heating system of a house works. As is observed from the illustration, the central heating machine comprises several mechanical aspects and forms a complex system. According to the given illustration, for the central heating machine to work the cold water supply is required and this water flows to the storage tank and the overflow pipe is there to store the excess water in storage. The water is passed through a boiler which is either gas or oil driven and a pump is connected with it. The radiators are connected with the boiler and these radiators are made of small tubes. When the cold water passes through the pump and boiler, it gains temperatures and become hot water and from the water taps, the house members get hot water. Thus the whole system that covers the house keeps it warm. In summary, the central heating system mainly works by flowing water through the house and increasing the temperature of it.
IELTS Writing Correction
- 1. Use system Original: central heating machine Suggested revision: central heating system Why it matters: The diagram shows a system, not a single machine.
- 2. Natural noun Original: mechanical aspects Suggested revision: components Why it matters: 'Components' is the appropriate word for parts of a system.
- 3. Add comma Original: for the central heating machine to work the cold water supply is required Suggested revision: for the central heating system to work, a cold water supply is required Why it matters: The introductory clause needs a comma and the noun phrase needs an article.
- 4. Process accuracy Original: the overflow pipe is there to store the excess water in storage Suggested revision: the overflow pipe removes excess water from the storage tank Why it matters: An overflow pipe does not store water; it carries excess water away.
- 5. Hyphenation Original: gas or oil driven Suggested revision: gas- or oil-driven Why it matters: Compound adjectives before a noun need hyphens.
- 6. Diagram accuracy Original: radiators are made of small tubes Suggested revision: radiators are connected by small tubes Why it matters: The diagram labels the tubes separately; it does not say radiators are made of them.
- 7. Verb agreement Original: it gains temperatures and become hot water Suggested revision: it gains heat and becomes hot water Why it matters: The singular subject 'it' needs 'becomes', and 'heat' is the natural noun.
- 8. Natural phrase Original: the house members Suggested revision: household members Why it matters: This is the standard phrase for people living in a house.
- 9. Clear result Original: Thus the whole system that covers the house keeps it warm Suggested revision: As a result, hot water circulates through the radiators and warms the house Why it matters: This makes the heating mechanism clearer.
- 10. Pronoun placement Original: increasing the temperature of it Suggested revision: raising its temperature Why it matters: This is a more natural grammatical structure.
- 11. Better overview Original: As is observed from the illustration, the central heating machine comprises several mechanical aspects and forms a complex system. Suggested revision: Overall, the system heats cold water in a boiler and circulates it through radiators and taps, while tanks and pipes control the water supply. Why it matters: This overview explains the purpose and main flow rather than just saying it is complex.
- 12. Fix first stage Original: According to the given illustration, for the central heating machine to work the cold water supply is required and this water flows to the storage tank and the overflow pipe is there to store the excess water in storage. Suggested revision: First, cold water enters the house and fills a storage tank; an overflow pipe is attached to prevent excess water from building up. Why it matters: The original is long and misdescribes the overflow pipe.
Suggested Rewrites
- central heating machine central heating system
- mechanical aspects components
- for the central heating machine to work the cold water supply is required for the central heating system to work, a cold water supply is required
- the overflow pipe is there to store the excess water in storage the overflow pipe removes excess water from the storage tank
- gas or oil driven gas- or oil-driven
- radiators are made of small tubes radiators are connected by small tubes
IELTS Writing Criteria Scores
Detailed feedback by IELTS writing criterion after the annotated essay.
Task Achievement
The response identifies the main components and gives a generally understandable process, but some details are inaccurate or vague. It does not clearly explain the full cycle from cold water supply to storage tank, boiler, radiators, hot taps, and return flow.
Describe the system step by step: cold water enters, is stored, passes to the boiler, is pumped through radiators and hot taps, and circulates through pipes.
Coherence and Cohesion
The answer has a basic sequence, but it is mostly one paragraph and the process stages are compressed into long sentences. The summary repeats the main idea without clarifying the cycle.
Use separate sentences for each stage and add sequence links such as 'first', 'then', 'after being heated', and 'finally'.
Lexical Resource
Vocabulary is understandable but sometimes inaccurate: 'machine', 'mechanical aspects', and 'gains temperatures' are not natural for this diagram.
Use process vocabulary such as 'system', 'components', 'flows', 'is heated', 'circulates', 'radiators', and 'pipes'.
Grammatical Range and Accuracy
There are frequent article, agreement, and verb-form errors, though the message is mostly clear. Some sentences are too long and need clearer subordination.
Rewrite passive process sentences carefully: 'water is heated', 'hot water is pumped', 'radiators are connected'.