# Plumbing Formulator vs testo Combustion App

The clearest difference is rating: Plumbing Formulator at 4.6 against testo Combustion App's 1.4. Plumbing Formulator also leads on update cadence (every 2 months vs every 7 months). testo Combustion App's advantage is in-app purchases (none vs 4) and iOS requirement (9.3 vs 18.6). On price, review sentiment, ratings volume and ads there is nothing between them.

Both are free to download. Plumbing Formulator sells 4 one-off in-app purchases. testo Combustion App asks for nothing beyond the download.

Plumbing Formulator holds the better App Store score, 4.6 against 1.4. Both are backed by a comparable volume of ratings — 7 and 10 respectively. Written reviews complicate that: 9% of Plumbing Formulator's written reviews are positive against 13% of testo Combustion App's, so the app with the better star average is not the one people write more warmly about.

Plumbing Formulator ships an update every 2 months, testo Combustion App every 7 months. The most recent releases landed on October 31, 2026 and October 29, 2026 respectively.

## The numbers

| Metric | Plumbing Formulator | testo Combustion App |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.6 (7 ratings)](https://appshunter.io/ios/app/plumbing-formulator/id303497783/reviews)** | [1.4 (10 ratings)](https://appshunter.io/ios/app/testo-combustion-app/id992414788/reviews) |
| Number of ratings | 7 | **10** |
| Positive reviews | 9.1% of reviews | **12.8% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 2 months** | Every 7 months |
| Monetization | Free | Free |
| Size | 123 MB | 62 MB |
| Requires iOS | 18.6 | **9.3** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Historycentral.com](https://appshunter.io/developer/1744330560) | [Testo SE & Co. KGaA](https://appshunter.io/developer/966489178) |

## What reviewers say

### Plumbing Formulator

[App page](https://appshunter.io/ios/app/plumbing-formulator/id303497783)

This professional calculator app provides over 200 formulas, calculators, and reference materials for plumbers, HVAC technicians, and mechanical contractors. It covers a wide range of calculations for water flow, piping, drainage, water heaters, pumps, and more, all in one pocket-sized tool.

**Highlights:** Over 200 formulas and calculators, Water flow and supply calculations, Pipe and piping calculations, Drainage and venting calculations, Water heater and pump calculations, Reference charts and code books, Pipe cut list optimizer

**Features:** macOS Compatibility, Family Sharing, Vision Pro support

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Version | $1.99 | one-time |
| Pro Purchase | $3.99 | one-time |
| Starter | $5.99 | one-time |
| Growth | $9.99 | one-time |


### testo Combustion App

[App page](https://appshunter.io/ios/app/testo-combustion-app/id992414788)

Control your testo 330 flue gas analyzer remotely from your smartphone or tablet. Create and send professional PDF reports with photos and your logo directly from the field, ensuring fast and efficient documentation.

**Highlights:** Remote start/stop of measuring instrument, Intuitive touchscreen menu, Graphical trend view, PDF report creation, Export measurement values to CSV, Customizable reports with logo, Bluetooth connectivity (20m range)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Plumbing Formulator free?

Plumbing Formulator is free to download, with in-app purchases available.

### Is testo Combustion App free?

testo Combustion App is free to download, with no in-app purchases.

### Which has better reviews, Plumbing Formulator or testo Combustion App?

Plumbing Formulator is rated higher. Plumbing Formulator averages 4.6 out of 5 from 7 ratings, while testo Combustion App averages 1.4 from 10 ratings.

### Do Plumbing Formulator or testo Combustion App have ads?

Neither Plumbing Formulator nor testo Combustion App shows ads.

### Which is updated more often, Plumbing Formulator or testo Combustion App?

Plumbing Formulator ships an update every 2 months, and testo Combustion App every 7 months. Most recently, Plumbing Formulator was updated on October 31, 2026 and testo Combustion App on October 29, 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.*