What is the best wireless high water bilge alarm monitor?
I keep my boat on a swinging mooring and I am paranoid about a seacock failing or a deck leak filling the bilge. I want a wireless high water alarm that will ping my phone if the water gets too high. What is the most reliable system on the market right now?
Answer
The best wireless high water bilge monitors currently available are the Siren 3 Pro for comprehensive vessel integration and the BRNKL system for standalone cellular monitoring. Both systems use a reliable high-water sensor wired to a 4G/5G cellular base station that sends instant push notifications or SMS alerts to your smartphone if the water rises above your primary bilge pump threshold.
Siren 3 Pro Integration
The Siren 3 Pro (now backed by Yamaha) sets the industry standard for expandable networks. The base unit costs around £650, plus an annual cellular subscription of roughly £160. It connects directly to your NMEA 2000 network and house battery bank. This NMEA 2000 link pulls in data from your GPS, depth sounder and wind instruments, displaying the boat's status on your phone.
For bilge monitoring, you wire a standard float switch into the Siren base unit. You can also use their wireless sensor nodes if routing cables from the bilge to the nav station proves difficult. These wireless nodes run on replaceable CR2032 coin-cell batteries that last about two years, though the float switch itself must still be hardwired to the node. The Siren app is highly polished and rarely suffers from server downtime.
Standalone Monitoring With BRNKL
The BRNKL (pronounced 'barnacle') system excels on remote swinging moorings. It costs around £750 for the base unit with a £200 annual subscription. BRNKL uses a global roaming SIM card to lock automatically onto the strongest local network, including Vodafone, EE or O2.
BRNKL features a built-in backup battery. If your boat loses main 12V power, the unit stays alive long enough to send an alert. You can wire up to four different bilge zones into a single BRNKL unit. This suits larger yachts with separate engine, midships and forward bilges.
Budget DIY Cellular Alternatives
A dedicated marine system might be overkill for smaller boats. You can build an effective wireless monitor using a standard 12V GSM relay switch like the RTU5024, which costs about £30 online.
- Buy a pre-paid data SIM card (often £5 a month) and insert it into the dialler.
- Mount the GSM dialler in a dry locker above the waterline inside an IP67 waterproof enclosure.
- Wire a high-quality float switch into the dialler's input terminals using 16 AWG tinned marine wire.
- When the float switch lifts, it closes the circuit and the dialler sends an SMS directly to your phone.