DTS Gas Guru | Privacy Policy

1. Who we are

DTS Gas Guru ("the app") is made by Black Water Tek, the trading name of William Goodman, a sole trader based in the United Kingdom. We are the controller of the personal data described in this policy. You can contact us at info@blackwatertek.com.

This policy explains what the app does with your information, in plain terms. The short version: without an account, nothing about you leaves your device. If you choose to create an account, we hold the small amount of data needed to sign you in and keep your mix library in step across your devices.

2. Using the app without an account

You do not need an account to use DTS Gas Guru. Without one:

All gas calculations run on your device. Your inputs and results are not sent anywhere.
Your settings, mixes and cylinders are stored on your device only.
There is no analytics, advertising, tracking or crash reporting of any kind.

One exception: opening a tool that shows plan information (for example the SCR calculator) asks our server for the list of available plans. That request contains no personal data, but, like any internet connection, it reveals your device's IP address to our hosting provider, which may keep it briefly in its request logs.

3. If you create an account

An account is optional. It lets you keep your mix library in step across devices. If you create one, we collect:

Your email address, used to sign you in and to send account emails (confirmation, password reset, security notices).
Your password, which we never store. We keep only a salted, one-way hash of it.
Your diver profile, if you fill it in: name, certification, number of logged dives, role and breathing rate (SAC).
Your mix and cylinder libraries: mix names, gas percentages, cylinder sizes, fill pressures and the limits you set, plus cylinder service details you enter.
Your plan status, recording that your account comes with Gas Guru.
Two-factor authentication details, only if you switch it on.
An encrypted key used for encrypted features. It is locked with your password, so we cannot read it.
Security records: the date, time and IP address of sign-ins and other security events, and for each signed-in device the IP address and device/browser type.
Account activity records, such as "password changed" or "profile updated", used to help us investigate problems you report.

Your profile and your mix and cylinder libraries are stored in a form we are able to read, so that they can be synced. We do not look at them except when you ask us to help with a problem.

4. Why we use it

To provide your account and sync (necessary to provide the service you asked for).
To keep accounts secure: detecting repeated failed sign-ins, limiting abuse and investigating security incidents (our legitimate interest in protecting you and the service).
To send you account emails you need, such as password resets. We do not send marketing emails.

We do not sell your data, use it for advertising, or use it to make automated decisions about you.

5. Who else handles your data

We use a small number of service providers, who process data only on our instructions:

Cloudflare: hosts our server and the database that stores account data.
Resend: sends account emails on our behalf.

These providers may process data outside the United Kingdom, including in the United States. Where they do, the transfer is covered by the safeguards UK data protection law requires.

Purchases of the app are handled entirely by the Apple App Store or Google Play under their own privacy policies. We do not receive your payment details.

6. How long we keep it

Account data is kept until you delete your account.
Sign-in security records are deleted after 90 days. Account activity records are deleted after 30 days.
Unconfirmed sign-ups are deleted after 24 hours.
When you delete your account, your email, password hash, profile, libraries, devices, sessions and activity records are deleted straight away. Security records from before the deletion lose your email and account link immediately and are deleted within 90 days.

7. Your rights

Under UK data protection law you can ask to see the data we hold about you, have it corrected, have it deleted, receive a copy of it, or object to how we use it. You can:

Delete your account yourself in the app, under Settings & Account. For your protection this asks for your password.
Email info@blackwatertek.com for anything else. We will reply within one month.

If you are unhappy with how we have handled your data, you can complain to the Information Commissioner's Office at ico.org.uk. We would appreciate the chance to put it right first.

8. Security

All connections to our server are encrypted in transit. Passwords are stored only as salted hashes, sign-in attempts are rate-limited, and two-factor authentication is available. Signing out ends the session on our server, not only on your device.

9. Children

DTS Gas Guru is intended for qualified technical divers and dive professionals. It is not directed at children under 13, and we do not knowingly collect their personal data.

10. Changes to this policy

If we change what the app collects, we will update this page and its effective date before the change reaches the app.

11. Contact us

Black Water Tek
William Goodman, trading as Black Water Tek
Email: info@blackwatertek.com

12. Safety disclaimer

DTS Gas Guru is a calculation aid only. It does not replace formal technical diving training, professional dive planning, or the expertise of a qualified dive instructor or gas blender. All gas blending must be performed by trained professionals using appropriate equipment. Black Water Tek accepts no liability for diving incidents arising from use of this application.