diff --git a/homeassistant/components/rainmachine/.translations/en.json b/homeassistant/components/rainmachine/.translations/en.json
index 54b67066f2b..4ad5bfd7c0d 100644
--- a/homeassistant/components/rainmachine/.translations/en.json
+++ b/homeassistant/components/rainmachine/.translations/en.json
@@ -1,5 +1,8 @@
 {
     "config": {
+        "abort": {
+            "already_configured": "This RainMachine controller is already configured."
+        },
         "error": {
             "identifier_exists": "Account already registered",
             "invalid_credentials": "Invalid credentials"
diff --git a/homeassistant/components/rainmachine/config_flow.py b/homeassistant/components/rainmachine/config_flow.py
index 4753335da78..4b93fc64159 100644
--- a/homeassistant/components/rainmachine/config_flow.py
+++ b/homeassistant/components/rainmachine/config_flow.py
@@ -1,7 +1,4 @@
 """Config flow to configure the RainMachine component."""
-
-from collections import OrderedDict
-
 from regenmaschine import login
 from regenmaschine.errors import RainMachineError
 import voluptuous as vol
@@ -29,8 +26,7 @@ def configured_instances(hass):
     )
 
 
-@config_entries.HANDLERS.register(DOMAIN)
-class RainMachineFlowHandler(config_entries.ConfigFlow):
+class RainMachineFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
     """Handle a RainMachine config flow."""
 
     VERSION = 1
@@ -38,16 +34,19 @@ class RainMachineFlowHandler(config_entries.ConfigFlow):
 
     def __init__(self):
         """Initialize the config flow."""
-        self.data_schema = OrderedDict()
-        self.data_schema[vol.Required(CONF_IP_ADDRESS)] = str
-        self.data_schema[vol.Required(CONF_PASSWORD)] = str
-        self.data_schema[vol.Optional(CONF_PORT, default=DEFAULT_PORT)] = int
+        self.data_schema = vol.Schema(
+            {
+                vol.Required(CONF_IP_ADDRESS): str,
+                vol.Required(CONF_PASSWORD): str,
+                vol.Optional(CONF_PORT, default=DEFAULT_PORT): int,
+            }
+        )
 
     async def _show_form(self, errors=None):
         """Show the form to the user."""
         return self.async_show_form(
             step_id="user",
-            data_schema=vol.Schema(self.data_schema),
+            data_schema=self.data_schema,
             errors=errors if errors else {},
         )
 
@@ -57,12 +56,11 @@ class RainMachineFlowHandler(config_entries.ConfigFlow):
 
     async def async_step_user(self, user_input=None):
         """Handle the start of the config flow."""
-
         if not user_input:
             return await self._show_form()
 
-        if user_input[CONF_IP_ADDRESS] in configured_instances(self.hass):
-            return await self._show_form({CONF_IP_ADDRESS: "identifier_exists"})
+        await self.async_set_unique_id(user_input[CONF_IP_ADDRESS])
+        self._abort_if_unique_id_configured()
 
         websession = aiohttp_client.async_get_clientsession(self.hass)
 
diff --git a/homeassistant/components/rainmachine/strings.json b/homeassistant/components/rainmachine/strings.json
index 6e26192ec82..7195cce2e31 100644
--- a/homeassistant/components/rainmachine/strings.json
+++ b/homeassistant/components/rainmachine/strings.json
@@ -14,6 +14,9 @@
     "error": {
       "identifier_exists": "Account already registered",
       "invalid_credentials": "Invalid credentials"
+    },
+    "abort": {
+      "already_configured": "This RainMachine controller is already configured."
     }
   }
 }
diff --git a/tests/components/rainmachine/test_config_flow.py b/tests/components/rainmachine/test_config_flow.py
index 9e43f647301..435e8fb33b5 100644
--- a/tests/components/rainmachine/test_config_flow.py
+++ b/tests/components/rainmachine/test_config_flow.py
@@ -5,6 +5,7 @@ from regenmaschine.errors import RainMachineError
 
 from homeassistant import data_entry_flow
 from homeassistant.components.rainmachine import DOMAIN, config_flow
+from homeassistant.config_entries import SOURCE_USER
 from homeassistant.const import (
     CONF_IP_ADDRESS,
     CONF_PASSWORD,
@@ -25,12 +26,33 @@ async def test_duplicate_error(hass):
         CONF_SSL: True,
     }
 
-    MockConfigEntry(domain=DOMAIN, data=conf).add_to_hass(hass)
+    MockConfigEntry(domain=DOMAIN, unique_id="192.168.1.100", data=conf).add_to_hass(
+        hass
+    )
     flow = config_flow.RainMachineFlowHandler()
     flow.hass = hass
 
-    result = await flow.async_step_user(user_input=conf)
-    assert result["errors"] == {CONF_IP_ADDRESS: "identifier_exists"}
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": SOURCE_USER}, data=conf
+    )
+    assert result["type"] == data_entry_flow.RESULT_TYPE_ABORT
+    assert result["reason"] == "already_configured"
+
+
+async def test_get_configured_instances(hass):
+    """Test retrieving all configured instances."""
+    conf = {
+        CONF_IP_ADDRESS: "192.168.1.100",
+        CONF_PASSWORD: "password",
+        CONF_PORT: 8080,
+        CONF_SSL: True,
+    }
+
+    MockConfigEntry(domain=DOMAIN, unique_id="192.168.1.100", data=conf).add_to_hass(
+        hass
+    )
+
+    assert len(config_flow.configured_instances(hass)) == 1
 
 
 async def test_invalid_password(hass):
@@ -44,6 +66,7 @@ async def test_invalid_password(hass):
 
     flow = config_flow.RainMachineFlowHandler()
     flow.hass = hass
+    flow.context = {"source": SOURCE_USER}
 
     with patch(
         "homeassistant.components.rainmachine.config_flow.login",
@@ -57,6 +80,7 @@ async def test_show_form(hass):
     """Test that the form is served with no input."""
     flow = config_flow.RainMachineFlowHandler()
     flow.hass = hass
+    flow.context = {"source": SOURCE_USER}
 
     result = await flow.async_step_user(user_input=None)
 
@@ -75,6 +99,7 @@ async def test_step_import(hass):
 
     flow = config_flow.RainMachineFlowHandler()
     flow.hass = hass
+    flow.context = {"source": SOURCE_USER}
 
     with patch(
         "homeassistant.components.rainmachine.config_flow.login",
@@ -104,6 +129,7 @@ async def test_step_user(hass):
 
     flow = config_flow.RainMachineFlowHandler()
     flow.hass = hass
+    flow.context = {"source": SOURCE_USER}
 
     with patch(
         "homeassistant.components.rainmachine.config_flow.login",