Pump Failure Alarm with Automatic Backup Aeration

DIY Voltage-Loss Alarm + Backup Pump for Koi Safety

Building a 120V relay alarm is a great start—but adding automatic backup aeration saves fish while you respond.

Simple Circuit Logic

1. Relay coil across pump power (120V).
2. When power fails, relay contacts close → activates:
3. Siren/strobe (alert)
4. 12V battery + inverter → backup air pump (or 12V DC air pump directly)

Practical Implementation

• Use a marine battery (deep cycle) + trickle charger.
• Connect a 12V DC air pump (e.g., Hakko, PondMaster) to battery via relay.
• Add a float switch in pond to prevent dry-running.
• House electronics in weatherproof box.

Why This Works

Oxygen is the first thing fish lose when the pump stops. A battery air pump runs 24–48+ hours on a charge—plenty of time to restore main power.

Commercial all-in-one units exist (e.g., PondGuard), but DIY is cheaper and customizable.