Your iPhone must be on your home Wi-Fi (not mobile data), the same network as the Control-R module. A guest network or a router setting that keeps devices apart can also block it.
The module must already have joined your home Wi-Fi (the 2.4 GHz network). Tankline cannot set up the module's Wi-Fi.
Allow Local Network access: Settings → Privacy & Security → Local Network → Tankline. Without it iOS blocks the connection.
"Find my water heater" takes about a minute. If nothing is found, look up the module in your router's list of connected devices and type its address instead.
The address can change after a router restart.
“Something answered, but it does not look like a Control-R module”
Something answered at the address you entered, but not a Control-R module. Check the address in your router's device list. Newer modules may not offer local access, and Tankline cannot connect to those. The free live view shows whether yours works, so you can check this before you buy Pro.
Hot water now does not start the recirculation
"Hot water now" needs a water heater with a recirculation pump. On a heater that reports none, the app shows one line instead of the button.
If the heater answered but did not start, the app tells you so, after a few seconds of checking. Look for a heater code or warning (the app shows it) and try again.
Not every module generation takes this command over the local connection.
Hot water now is part of Tankline Pro. In the free version the button shows a lock and opens the Pro screen; nothing is sent to the heater.
The temperature will not change
Changing the temperature is part of Tankline Pro. The app moves only in the steps your heater accepts, inside the limits it reports. If the heater keeps its old setting, the app tells you.
The connection drops
While the app is open, Tankline reads the heater every few seconds and reconnects by itself. When the app is closed it keeps no connection. The status line shows when the reading was last updated, or when the heater was last seen.
Can I use Tankline away from home?
No. Tankline talks to your water heater only on your home network and has no cloud service, so there is no account, subscription or server involved.
Restore Tankline Pro
Settings → Restore Purchases, signed in with the same Apple Account. Refunds are requested from Apple at reportaproblem.apple.com.
Privacy
See the privacy policy. Tankline has no account and no server; nothing leaves your home network.