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Why does water left in bottles start to smell bad after a few days?

Sarah Jenkins
Sarah Jenkins
Lead Content Curator · Apr 8, 2026 · Updated Apr 13, 2026

It goes off. Water isn't sterile, it has bacteria in it like just about every other foodstuff. A few days at room temperature and you have a bacteria field-day.

29
Words

1 min
Read Time

#403
of 500 in Space & Astronomy

-57%
vs Category Avg

The Short Answer

It goes off. Water isn't sterile, it has bacteria in it like just about every other foodstuff. A few days at room temperature and you have a bacteria field-day.

Analysis

Key Concepts: Bacteria, goes, water

This explanation focuses on bacteria, goes, water and spans 29 words across 3 sentences. At 57% below the average Space & Astronomy explanation (68 words), the answer takes a direct, no-frills approach — sometimes the simplest explanation is the most effective.

What This Answer Covers

The explanation opens with: “It goes off.” It then elaboratesultimately building toward a complete picture across 3 connected points.

How This Compares in Space & Astronomy

Ranked #403 of 500 Space & Astronomy questions by answer depth (top 81%). This is a brief primer — the answer is intentionally short. For questions with a single core mechanism, brevity can actually be a strength.

Frequently Asked Questions

Is there a simple explanation for why water left in bottles start to smell bad after a few days?

It goes off. Water isn't sterile, it has bacteria in it like just about every other foodstuff. A few days at room temperature and you have a bacteria field-day.

How detailed is this explanation compared to similar Space & Astronomy questions?

This is a brief answer at 29 words, ranked #403 of 500 Space & Astronomy questions by depth. The key concepts covered are bacteria, goes, water.

What approach does this answer take to explain water left in bottles start to smell bad after a few days?

The explanation uses direct explanation across 29 words. It is categorized under Space & Astronomy and addresses the question through 1 analytical lens.