Testwater privacy policy

Last updated: 19 October 2026 · Testwater for iPhone

The short version

• There's no account to create, and Testwater has no server of ours to talk to: it sends nothing to us. It opens pages on mirentha.com only when you tap one of its links to them.
• Your tanks, readings, tasks and doses are stored on your iPhone. We never receive them.
• Your records leave the app only when you send them, as a CSV or backup file you share, and in your iPhone's own backups.
• There are no analytics, no advertising, no tracking and no third-party code in the app.
• Subscriptions are sold and handled by Apple. We never see your payment details.

1. Who we are

Testwater is made by Mirentha Ltd ("Mirentha", "we", "us"), a company incorporated in England and Wales (company number 17207914) with its registered office at 71-75 Shelton Street, Covent Garden, London, WC2H 9JQ.

For anything about privacy, write to [email protected] or to the address above. Our website privacy policy covers visits to mirentha.com and emails you send us.

2. What Testwater keeps, and where

Your records

Everything you enter: your tanks (name, type, volume, notes and the date you added each one), the parameters and target ranges you set, your readings (the value, whether it was below or above what the kit can show, when the test was taken, when you entered it and any note), your maintenance tasks with their history and reminder times, the dosing products you describe from their labels, your fertiliser plans and the doses you log.

These are stored in Testwater's own storage on your iPhone. They aren't synced to iCloud or anywhere else: Testwater has no iCloud sync. Anyone who can use your iPhone can open the app and see them. We can't, because nothing is sent to us.

Settings on this iPhone

The units you chose (temperature, volume and alkalinity), whether the welcome screen has been shown, and three notes about Testwater Plus: whether it was active the last time the app checked, which plan it was, and whether an Apple Account used with Testwater on this iPhone has ever had Plus. They let the app know the answer before the App Store replies, and show "Plus has ended" in Settings rather than "Free" once a subscription has ended. For Apple's rating prompt they also hold how many tests you have saved and the version of the app that last asked Apple to show the prompt, so that Testwater asks no more than once a version and never before your third test. These are kept in the app's settings on your iPhone.

Copies saved before a restore or an import

Before you restore a backup or a saved copy, or import a CSV file, Testwater saves a full copy of what's on the iPhone at that moment (unless there's nothing on it yet), so Restore previous data can bring it back if the restore or import wasn't what you wanted. It keeps the three most recent copies of each kind on your iPhone and deletes older ones. You can delete any copy yourself: Settings › Import and export › Restore previous data, then swipe to delete.

Our lawful basis

Because Testwater sends us nothing, Mirentha doesn't collect or process any personal data through the app, so there's no lawful basis to state and nothing we hold about you from it. The crash reports and usage statistics Apple may share with us if you opt in (section 6) come from Apple, not from the app, and Apple doesn't give us your identity with them. What's on your iPhone is under your control.

3. What leaves your iPhone, and only when you choose

• Exported readings. Export readings (CSV) creates a file named testwater-readings-date.csv with every reading from every tank, hidden parameters included, in your chosen units: tank, parameter, time, value, unit, whether it was a less-than or greater-than reading, and note.
• Backups. Export backup creates a file named testwater-backup-date.json with everything you've recorded in the app, so it can be restored on another iPhone. Your unit settings and the app's other settings on this iPhone aren't included.
• Both files go through the iOS share sheet to wherever you choose to send or save them. To hand a file to the share sheet, Testwater writes it to its temporary folder on your iPhone, which iOS clears. We never see them. Once a file has left Testwater, it's handled by wherever you sent it.
• Files you import. When you import a CSV file or restore a backup, you choose the file in the Files picker. Testwater reads it once and keeps what's in it (the readings and notes from a CSV file, with any parameters they need, or everything in a backup), not the file itself.
• Your iPhone's own backups. Like most apps' data, Testwater's is included in your iPhone's backups if you use iCloud Backup or back up to a computer. Those backups are kept by Apple under your Apple Account, or on your computer, not by us.
• Links. Terms of Use, Privacy Policy and Support in the app's Settings, the Terms of Service and Privacy Policy links on the subscription screen, and Contact support on the screen shown if the app can't open its data all open pages on mirentha.com. The app sends nothing with them, and a visit to the site is covered by our website privacy policy.

4. Reminders

Task reminders are notifications your iPhone schedules for itself. They don't pass through any server. Testwater asks your permission the first time you switch on a reminder for a task, when you tap Turn on reminders in Tasks or when you restore a backup that has reminders switched on, and never before.

A reminder shows the task and the tank, for example "Water change due · Reef 250", with how often the task comes round and when it was last done. It can appear on your Lock Screen, where anyone holding the phone can read it. Tapping Done on a reminder marks the task done on your iPhone.

Switch a reminder off in the task, or turn all of Testwater's notifications off in Settings › Apps › Testwater › Notifications.

5. Purchases

Testwater Plus is an auto-renewable subscription sold by Apple through the App Store. Apple processes the payment, and we never see your card or Apple Account details. To know whether Plus is active, the app asks the App Store on your iPhone; that exchange is between your iPhone and Apple. We receive Apple's sales and subscription reports, which don't tell us who you are. Apple's handling of purchases is covered by Apple's privacy policy.

6. Apple services and third parties

Testwater shares no data with any third party, and contains no third-party code: no analytics, advertising, crash-reporting or tracking services. It uses only Apple's own frameworks, and the Apple services it relies on are the App Store, for purchases and for Apple's rating prompt (Apple shows it, and Testwater never learns what you answer), and your iPhone's notifications, for reminders. Apple describes how it handles information in its privacy policy.

If you've chosen to share analytics with app developers (Settings › Privacy & Security › Analytics & Improvements), Apple may share crash reports and usage statistics with us. We use them only to find and fix problems; Apple describes how it keeps them in its privacy policy. You can turn this off at any time in the same place.

7. Keeping and deleting your data

Your records stay on your iPhone until you delete them. In Testwater you can delete a reading, a task or one of its ticks, a dose, a product (in the dosing calculator, which needs Plus), a parameter with its readings (Show or add parameters on the tank's screen, then swipe it) or a whole tank with everything recorded for it (Edit on the tank's screen, then Delete tank, and type the tank's name to confirm). On a read-only tank, only the whole tank can be deleted. A tank's fertiliser plan is deleted with the tank. The copies saved before a restore or an import can be deleted in Restore previous data. Deleting the Testwater app deletes everything it stored on your iPhone.

Files you exported, and your iPhone's own backups, are yours to delete wherever you keep them.

You can change Testwater's notification permission at any time in Settings › Apps › Testwater › Notifications.

8. Your rights

Under the UK GDPR you have the right to access, correct, erase, restrict and move personal data held about you, and to object to how it's used. Testwater sends us nothing, so we hold no personal data from the app. Your records are on your iPhone, where you can see, correct and delete them yourself, and export them as a CSV file or a backup to take them elsewhere.

If you write to us, for support or anything else, we handle your email as our website privacy policy describes, and you can exercise your rights over it by writing to [email protected]. If you're unhappy with how we've handled your data, please tell us first so we can try to put it right. You also have the right to complain to the Information Commissioner's Office (ICO) at ico.org.uk/make-a-complaint.

9. Children

Testwater isn't directed at children under 13, and it collects no personal data from anyone, children included.

10. Changes to this policy

If a version of Testwater handles data differently, we'll update this policy before that version is released and change the date at the top. The current version is always on this page.

11. Contact

Mirentha Ltd, 71-75 Shelton Street, Covent Garden, London, WC2H 9JQ. Email [email protected] about privacy, or use the support form about anything else.