# ChatLink DUO vs Wastewater Operator Exam Prep

The clearest difference is in-app purchases: ChatLink DUO at none against Wastewater Operator Exam Prep's 3. ChatLink DUO also leads on device support (3 vs 1) and iOS requirement (15.1 vs 18.0). Wastewater Operator Exam Prep's advantage is update cadence (daily vs every 46 months). On price and ads there is nothing between them.

Both are free to download. Wastewater Operator Exam Prep sells 3 in-app purchases, starting at $9.99 per month. ChatLink DUO asks for nothing beyond the download.

ChatLink DUO ships an update every 46 months, Wastewater Operator Exam Prep daily. The most recent releases landed on October 27, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | ChatLink DUO | Wastewater Operator Exam Prep |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.5 (11 ratings)](https://appshunter.io/ios/app/wastewater-operator-exam-prep/id6762569325/reviews)** |
| Number of ratings | — | **11** |
| Positive reviews | — | 0.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 46 months | **Daily** |
| Monetization | — | Freemium |
| Size | 61 MB | 21 MB |
| Requires iOS | **15.1** | 18.0 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 9+ | 4+ |
| Developer | [Dalton Utilities / OptiLink](https://appshunter.io/developer/1628633240) | [Alexander Parnev](https://appshunter.io/developer/1645934480) |

## What reviewers say

### ChatLink DUO

[App page](https://appshunter.io/ios/app/chatlink-duo/id1628633238)

**Features:** macOS Compatibility

**In-app purchases:** none


### Wastewater Operator Exam Prep

[App page](https://appshunter.io/ios/app/wastewater-operator-exam-prep/id6762569325)

Prepare for your wastewater treatment operator certification exam with a comprehensive study guide. Access over 1000 practice questions, detailed explanations, flashcards, and an AI tutor to master all five key content areas. Track your progress and simulate exam conditions to ensure you're ready for certification.

**Highlights:** 1000+ practice questions, Detailed answer explanations, Full exam simulation, AI tutor for concept explanation, Glossary of terms, Swipeable flashcards, Progress tracking

**Features:** macOS Compatibility

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Full Access | $9.99 | per month |
| Full Access | $59.99 | per year |
| Full Access | $99.99 | one-time |


## Frequently asked questions

### Is ChatLink DUO free?

ChatLink DUO is free to download, with no in-app purchases.

### Is Wastewater Operator Exam Prep free?

Wastewater Operator Exam Prep is free to download, with in-app purchases available.

### Do ChatLink DUO or Wastewater Operator Exam Prep have ads?

Neither ChatLink DUO nor Wastewater Operator Exam Prep shows ads.

### Which is updated more often, ChatLink DUO or Wastewater Operator Exam Prep?

ChatLink DUO ships an update every 46 months, and Wastewater Operator Exam Prep daily. Most recently, ChatLink DUO was updated on October 27, 2026 and Wastewater Operator Exam Prep on October 25, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*