Bilge & flood alarms

A battery sensor at the low point that sleeps for years and reports the second water reaches it — the alarm every boat and rig needs, whatever else you install.

High water is the universal failure. Rain past a tired cover, a weeping stuffing box, a packing gland that let go, a bilge pump quietly losing to a slow leak, a water-heater drip in an RV's wet bay — none of these need a city-water hookup, and all of them end badly if the first person to notice is a dock neighbor a week later. The bilge alarm is the piece of Guardian that covers every one of them.

What happens in the seconds after water touches a sensor t = 0 ~16 s 🌊 Water touches the sensor it wakes from deep sleep instantly 📡 Alarm webhook fires straight to the Guardian cloud — seconds 📲 Everyone is told push to every member, on every plan 💧🔒 Valve closes automatically if you have one — city-water setups Aboard with the app open, the in-app Flooding Sentry sounds immediately on the local network — no internet involved. The cloud path above is what protects you with the app closed.
Battery flood sensors deep-sleep for years, then report the moment it matters. Alarms are never throttled and never tier-gated.

The hardware

Guardian uses the Shelly Flood Gen4 (~$30): battery-powered, waterproof contacts, and built to deep-sleep — it wakes on its own schedule to check in and wakes instantly when its contacts get wet, firing its alarm straight to the Guardian cloud. Years on a coin cell, no wiring.

Deep sleep means a flood sensor can look "quiet" in the app right after setup — that's normal, and it's why Guardian never polls battery sensors (polling would show false "down" states and drain them). They speak when they have something to say, and staleness is judged by their check-in cadence.

Placement

  • The bilge low point — wherever water collects first. This is the one every boat should have.
  • Under known weep points — the water heater, the head, the galley sink, an RV's wet bay. Slow drips get caught while they're still drips.
  • One per compartment that matters — sensors are cheap; hauling out isn't. Multiple sensors also tell you where the water is.

Aboard and away

  • Aboard, app open: the in-app Flooding Sentry sounds immediately over the local network — no internet involved, free on every plan.
  • Away, app closed: the sensor's webhook reaches the Guardian cloud in seconds, and a push goes to every member of the vehicle, on every plan. Flood alarms are never throttled, never coalesced away, and never tier-gated.

If you're hooked to city water

A flood alarm can also act: with a LinkTap valve on the dock or pedestal spigot, the cloud closes the valve automatically — measured at about 16 seconds from alarm to valve-close command; the valve itself comes with any paid plan. That combination (and why the valve belongs at the source, not the inlet) has its own pages: Water control & safety and the city-water use case. No valve? The alarm above is complete on its own — the valve is the city-water add-on, not a prerequisite.

Test it — actually

A protection system you've never tested is a hope, not a system. Touch the sensor's contacts with a wet cloth: expect the local siren if the app is open aboard, and the push on your phone either way. Do it once at install and once at the start of each season — it takes ten seconds and it's the only way to know the whole chain works.

← Location & security Water control & safety →