# Watermaker MQTT API Reference

Reference for UI/dashboard developers integrating with the watermaker system over MQTT.

## Connection

| Parameter | Default | Environment Variable |
|-----------|---------|---------------------|
| Broker host | `198.18.4.108` | `MQTT_BROKER_HOST` |
| Broker port | `1883` | `MQTT_BROKER_PORT` |
| SSL/TLS | `false` | `MQTT_BROKER_SSL` |
| Topic prefix | `watermaker` | `MQTT_TOPIC_PREFIX` |

All topics below use the default `watermaker` prefix.

### Availability (Last Will and Testament)

Subscribe to `watermaker/availability` to detect when the watermaker API is online or offline.

| Value | Meaning |
|-------|---------|
| `online` | API is connected and publishing |
| `offline` | API disconnected (set automatically by broker via LWT) |

This topic is **retained** -- you receive the last known state immediately on subscribe.

---

## Data Topics (Server to Dashboard)

Real-time PLC data. Payloads are JSON.

### `watermaker/status`

System status. Published when status changes (mode, step, operating mode, valve positioning, or active timer changes).

**Retained: Yes | QoS: 0**

```json
{
  "system": {
    "mode": 7,
    "mode_name": "DTS",
    "operating_mode": "dts",
    "status": 3,
    "status_name": "Running",
    "valve_positioning": false,
    "active_timer": null
  },
  "connection": {
    "connected": true,
    "last_update": "2026-01-04T10:30:00Z"
  }
}
```

| Field | Type | Description |
|-------|------|-------------|
| `system.mode` | int | Raw R1000 mode register |
| `system.mode_name` | string | Human-readable mode name |
| `system.operating_mode` | string | `idle`, `single_pass`, `double_pass`, `dts`, `fw_flush` |
| `system.status` | int | Production step (R1036): 0=Idle, 1=Prime, 2=Init, 3=Run, 4=Stop, 5=Flush |
| `system.status_name` | string | Human-readable step name |
| `system.valve_positioning` | bool | True during valve positioning phase |
| `system.active_timer` | object/null | Currently active timer info |
| `connection.connected` | bool | PLC connection status |

---

### `watermaker/sensors`

Sensor readings. Published every 1-2s during operation, every 60s when idle.

**Retained: No | QoS: 0**

```json
{
  "pressure": {
    "feed": 45.2,
    "membrane": 820.5,
    "product": 12.3
  },
  "temperature": {
    "feed": 75.4,
    "system": 78.2
  },
  "flow": {
    "brine": 2.8,
    "product_1": 1.2,
    "product_2": 1.0
  },
  "quality": {
    "ppm": 245
  }
}
```

| Field | Type | Unit | Description |
|-------|------|------|-------------|
| `pressure.feed` | float | PSI | Feed water pressure |
| `pressure.membrane` | float | PSI | Membrane pressure |
| `pressure.product` | float | PSI | Product water pressure |
| `temperature.feed` | float | F | Feed water temperature |
| `temperature.system` | float | F | System temperature |
| `flow.brine` | float | GPM | Brine flow rate |
| `flow.product_1` | float | GPM | First pass product flow |
| `flow.product_2` | float | GPM | Second pass product flow |
| `quality.ppm` | int | PPM | Total dissolved solids |

---

### `watermaker/timers`

Timer values. Published every polling cycle.

**Retained: No | QoS: 0**

```json
{
  "production_timer": {
    "priming": 165.5,
    "initialize": 6553.5,
    "ppm_stabilization": 6553.5,
    "stop": 6553.5,
    "flush": 6553.5,
    "sw_valve_positioning": 6553.5,
    "dts_valve_positioning": 6553.5,
    "fwf": 6553.5
  },
  "fwf_timer": {
    "countdown": 6553.5
  }
}
```

A value of `6553.5` indicates the timer is inactive.

---

### `watermaker/counters`

Water production counters. Published every 30s during production, 60s when idle.

**Retained: Yes | QoS: 0**

```json
{
  "single_pass_since_last": 125.4,
  "double_pass_since_last": 0.0,
  "dts_since_last": 450.2,
  "total_product": 12500.8,
  "total_brine": 25001.6
}
```

| Field | Type | Unit | Description |
|-------|------|------|-------------|
| `single_pass_since_last` | float | gallons | Single pass production since last reset |
| `double_pass_since_last` | float | gallons | Double pass production since last reset |
| `dts_since_last` | float | gallons | DTS production since last reset |
| `total_product` | float | gallons | Lifetime product water total |
| `total_brine` | float | gallons | Lifetime brine total |

---

### `watermaker/outputs`

Digital output states. Published every polling cycle.

**Retained: Yes | QoS: 0**

```json
{
  "low_pressure_pump": 1,
  "high_pressure_pump": 1,
  "boost_pump": 0,
  "product_solenoid_1": 1,
  "product_solenoid_2": 0,
  "brine_solenoid": 1
}
```

Values: `1` = on, `0` = off.

---

### `watermaker/tank_update`

Fresh water tank levels from Victron Venus OS. Published every 10 seconds.

**Retained: Yes | QoS: 0**

```json
{
  "connected": true,
  "portal_id": "abc123",
  "tanks": {
    "bow": {
      "name": "Water Bow",
      "level_percent": 72.5,
      "capacity_gallons": 90.0,
      "gallons_stored": 65.25,
      "last_update": 1704361800.0
    },
    "stern": {
      "name": "Water Stern",
      "level_percent": 45.0,
      "capacity_gallons": 90.0,
      "gallons_stored": 40.5,
      "last_update": 1704361800.0
    }
  },
  "total_gallons": 105.75,
  "total_capacity": 180.0,
  "total_percent": 58.75,
  "timestamp": "2026-01-04T10:30:00"
}
```

---

## Event Topics (Server to Dashboard)

One-time event notifications. Payloads are JSON.

### `watermaker/production/started`

Published when production begins.

**Retained: No | QoS: 1**

```json
{
  "mode": "dts",
  "timestamp": "2026-01-04T10:30:00"
}
```

### `watermaker/production/stopped`

Published when production ends.

**Retained: No | QoS: 1**

```json
{
  "mode": "dts",
  "timestamp": "2026-01-04T10:30:00"
}
```

### `watermaker/production/limit`

Production limit tracking update. Published every cycle during active production.

**Retained: No | QoS: 0**

```json
{
  "is_tracking": true,
  "mode": "dts",
  "run_type": "fill",
  "gallons_produced": 23.5,
  "elapsed_seconds": 720,
  "gallon_limit": 50.0,
  "time_limit_seconds": null,
  "progress_percent": 47.0,
  "eta_seconds": 800,
  "flow_rate_gpm": 2.1,
  "tank_fill": {
    "bow_level": 72.5,
    "stern_level": 45.0,
    "total_remaining_gallons": 64.25,
    "target_level": 90,
    "eta_seconds": 1830
  }
}
```

### `watermaker/production/limit_reached`

Published when a production limit is reached.

**Retained: No | QoS: 1**

```json
{
  "type": "gallon",
  "value": 50.0,
  "reason": "Gallon limit of 50.0 gallons reached",
  "timestamp": "2026-01-04T11:00:00"
}
```

---

### `watermaker/verification/state_verified`

Published when a predicted state transition was correct.

**Retained: No | QoS: 1**

```json
{
  "command_type": "start",
  "verification_time_ms": 150.25,
  "timestamp": "2026-01-04T10:30:00Z"
}
```

### `watermaker/verification/state_correction`

Published when the actual state differs from the prediction.

**Retained: No | QoS: 1**

```json
{
  "expected": {
    "status": 0,
    "status_name": "Valve Positioning",
    "operating_mode": "dts"
  },
  "actual": {
    "status": 1,
    "status_name": "Priming",
    "operating_mode": "dts"
  },
  "command_type": "start",
  "timestamp": "2026-01-04T10:30:00Z"
}
```

### `watermaker/verification/timer_correction`

Published when a timer drifts more than 2 seconds from its expected value.

**Retained: No | QoS: 0**

```json
{
  "timer_id": "priming",
  "actual_value": 165.5,
  "expected_value": 168.0,
  "drift_seconds": 2.5,
  "timestamp": "2026-01-04T10:30:00Z"
}
```

---

### `watermaker/remote_change`

Published when a state change is detected from the physical HMI panel (not from API or dashboard).

**Retained: No | QoS: 1**

```json
{
  "type": "remote_start",
  "previous_step": 0,
  "current_step": 1,
  "previous_mode": null,
  "current_mode": "single_pass",
  "message": "Production started externally (single_pass)",
  "timestamp": "2026-01-04T10:30:00"
}
```

| `type` Value | Description |
|-------------|-------------|
| `remote_start` | Production started from HMI |
| `remote_stop` | Production stopped from HMI |
| `remote_skip` | Phase skipped from HMI |
| `remote_mode_change` | Operating mode changed from HMI |
| `remote_step_change` | Step changed from HMI |
| `flush_complete` | Flush completed |

---

### `watermaker/consumable_warning`

Published when a consumable approaches or exceeds its replacement limit.

**Retained: No | QoS: 1**

```json
{
  "item": "pre_filter",
  "name": "Pre-Filter",
  "level": 85.2,
  "remaining": 14.8,
  "unit": "gallons",
  "severity": "warning",
  "timestamp": "2026-01-04T10:30:00"
}
```

| `severity` | Trigger |
|-----------|---------|
| `warning` | 80%+ of lifespan consumed |
| `critical` | 100%+ of lifespan consumed |

---

### `watermaker/alarm`

Published when a PLC alarm is detected.

**Retained: No | QoS: 1**

```json
{
  "alarm_code": "HIGH_PRESSURE",
  "message": "High pressure alarm triggered",
  "timestamp": "2026-01-04T10:30:00Z"
}
```

### `watermaker/error`

Published on system errors.

**Retained: No | QoS: 1**

```json
{
  "message": "PLC communication timeout",
  "timestamp": "2026-01-04T10:30:00"
}
```

---

## Command Topics (Dashboard to Server)

Publish to these topics to control the watermaker. Commands are only processed when `MQTT_COMMANDS_ENABLED=true` (disabled by default for safety).

Responses are published to `watermaker/command/response` with QoS 1.

### `watermaker/command/start`

Start a watermaker production sequence.

```json
{
  "mode": "dts",
  "run_type": "fill",
  "gallon_limit": 50.0,
  "time_limit": 3600,
  "expected_gallons": 45.0
}
```

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `mode` | string | **Yes** | `single_pass`, `double_pass`, `dts`, or `fw_flush` |
| `run_type` | string | No | `fill`, `gallons`, `timer`, `boat_wash`, or `manual` |
| `gallon_limit` | float | No | Max gallons before auto-stop (not valid for `fw_flush`) |
| `time_limit` | int | No | Max seconds before auto-stop |
| `expected_gallons` | float | No | Pre-safety-margin estimate for Fill mode |

**Mode descriptions:**

| Mode | Description |
|------|-------------|
| `single_pass` | Seawater through single membrane |
| `double_pass` | Seawater through both membranes |
| `dts` | Dockside Treatment System (freshwater source) |
| `fw_flush` | Fresh water flush (maintenance cycle) |

**Run type descriptions:**

| Run Type | Description |
|----------|-------------|
| `fill` | Run until tanks reach target level (uses `expected_gallons`) |
| `gallons` | Run until `gallon_limit` is reached |
| `timer` | Run until `time_limit` is reached |
| `boat_wash` | Short run for deck wash water |
| `manual` | Manual run, no auto-stop |

### `watermaker/command/stop`

Stop current production. No payload required.

```json
{}
```

The API automatically selects the correct stop command based on the current production step (priming/init stop, running stop, or flush stop).

### `watermaker/command/skip`

Skip the current phase. No payload required. Only valid during priming (step 1) or initializing (step 2).

```json
{}
```

### `watermaker/command/cancel_limit`

Cancel production limit tracking without stopping production. No payload required.

```json
{}
```

### `watermaker/command/response`

Responses to commands are published here.

**Success:**

```json
{
  "success": true,
  "command": "start",
  "mode": "dts",
  "message": "DTS sequence started successfully",
  "predicted_state": {
    "system": {
      "status": 0,
      "status_name": "Valve Positioning",
      "operating_mode": "dts"
    }
  },
  "timestamp": "2026-01-04T10:30:00Z"
}
```

**Error:**

```json
{
  "success": false,
  "error": "INVALID_MODE",
  "message": "Invalid mode. Valid modes: single_pass, double_pass, dts, fw_flush",
  "timestamp": "2026-01-04T10:30:00Z"
}
```

---

## Update Frequencies

| Topic | Idle | Operating | Notes |
|-------|------|-----------|-------|
| `sensors` | 60s | 1-2s | Every 60s when idle for monitoring; spread polling when operating |
| `timers` | 5s | 1-2s | Spread polling alternates even/odd seconds |
| `status` | On change | On change | Only published when fields change |
| `counters` | 60s | 30s | |
| `outputs` | 5s | 1-2s | |
| `tank_update` | 10s | 10s | From Victron Venus OS |
| `production/limit` | -- | Every cycle | Only during active production |

---

## WebSocket to MQTT Migration

For UI developers migrating from Socket.IO to MQTT.

### Event Mapping

| Socket.IO Event | MQTT Topic | Retained |
|-----------------|------------|----------|
| `status` | `watermaker/status` | Yes |
| `sensors` | `watermaker/sensors` | No |
| `timers` | `watermaker/timers` | No |
| `counters` | `watermaker/counters` | Yes |
| `outputs` | `watermaker/outputs` | Yes |
| `state_verified` | `watermaker/verification/state_verified` | No |
| `state_correction` | `watermaker/verification/state_correction` | No |
| `timer_correction` | `watermaker/verification/timer_correction` | No |
| `remote_change` | `watermaker/remote_change` | No |
| `production_started` | `watermaker/production/started` | No |
| `production_stopped` | `watermaker/production/stopped` | No |
| `production_limit` | `watermaker/production/limit` | No |
| `limit_reached` | `watermaker/production/limit_reached` | No |
| `tank_update` | `watermaker/tank_update` | Yes |
| `consumable_warning` | `watermaker/consumable_warning` | No |
| `alarm` | `watermaker/alarm` | No |
| `error` | `watermaker/error` | No |

### Key Differences from WebSocket

- **Retained messages** replace the on-connect full state push. New MQTT subscribers automatically receive the last known value for retained topics (status, counters, outputs, tank_update).
- **No explicit connect/subscribe handshake.** Subscribe to the topics you need. Use `watermaker/#` to receive everything.
- **Wildcard subscriptions** are supported: `watermaker/production/#` for all production events, `watermaker/verification/+` for all verification events.
- **Commands** go through MQTT publish instead of REST POST endpoints. The payload and validation logic are identical.
- **Availability monitoring** via `watermaker/availability` (retained LWT) replaces Socket.IO connect/disconnect events.

### Quick Start (JavaScript with MQTT.js)

```javascript
import mqtt from 'mqtt';

const client = mqtt.connect('mqtt://198.18.4.108:1883');

client.on('connect', () => {
  client.subscribe('watermaker/#');
});

client.on('message', (topic, message) => {
  const data = JSON.parse(message.toString());

  switch (topic) {
    case 'watermaker/status':
      updateStatus(data);
      break;
    case 'watermaker/sensors':
      updateSensors(data);
      break;
    case 'watermaker/timers':
      updateTimers(data);
      break;
    case 'watermaker/counters':
      updateCounters(data);
      break;
    case 'watermaker/tank_update':
      updateTanks(data);
      break;
    case 'watermaker/availability':
      updateConnectionStatus(message.toString());
      break;
  }
});

// Start production
function startProduction(mode, options) {
  client.publish('watermaker/command/start', JSON.stringify({
    mode: mode,
    run_type: options.run_type,
    gallon_limit: options.gallon_limit,
    time_limit: options.time_limit,
    expected_gallons: options.expected_gallons
  }));
}

// Listen for command responses
client.subscribe('watermaker/command/response');
```