Would you know if water was filling your bilge BEFORE it got over the floorboards? The sooner you know, the better your chance of saving the boat.

Bilge Alarm

A couple of weeks ago, we got the horrible news that another Gemini took on water and sank underway to the Bahamas. The two people aboard were rescued by their buddy boat with no injuries but the boat was lost.

The owner has publicly said that they discovered two inches of water over the floorboards in one hull around midnight, were unable to find where the water was coming from, and within twenty minutes had to abandon the boat as it was about to capsize due to all the water in one hull.

That got Dave and I thinking. Barefoot Gal did not have any sort of “early warning system” of water intrusion. Our previous boat, a Tayana 37 with deep bilges, had a very loud alarm on the primary bilge pump – if the pump ran, you knew it. And you could/would investigate.

Twice it alerted us to a problem: one when the fresh water tank developed a leak and once when the stuffing box was reinstalled upside down after having been worked on.

We both think that in order to have any chance of saving the boat in the event of a thru-hull failure or any other water intrusion, you have to know about it as soon as possible. (You also have to have the tools and a plan to stop the leak.)

So I started looking at bilge alarms from various marine sources. And I discovered that they tended to be expensive, hard-wired (hence, time-consuming to install) and most were designed for a light and alarm at the helm. Nothing wrong with them, but just seemed like overkill for a boat like ours. We don’t believe in “cheaping out” when it comes to safety equipment, but we thought that something simpler would actually be better.

Continuing to search, I was able to find a better solution for our needs: a home “leak detector.” They’re designed to sound an alarm (it sounds similar to a smoke detector) when water is detected and are typically used near hot water heaters, washing machines, dishwashers, under sinks and toilets and near sumps. Luckily, one listed “boat bilges” as a possible use and Google picked up on it! (Disclaimer: while we thought these were right for us, you have to decide if they’re right for you.)

Would you know if water was filling your bilge BEFORE it got over the floorboards? The sooner you know, the better your chance of saving the boat.

You place the unit on its back where you want to detect water. If water contacts both of those sensor wires, the alarm will sound.

They’re pretty small (a little larger than a deck of cards) and most run off a 9-volt battery. No installation, either – just pop in the battery, test it and place it where you want it.

Several different companies make leak detectors and each has at least a couple models. After looking at many product listings and reviews on Amazon, I started picking up on some differences:

  • Some are single-use and come with the battery preinstalled: they’re slightly cheaper but you can’t test them and if they get wet once (say you leave a hatch open, it rains and water gets in the bilge) they have to be replaced.
  • Some do not float – if there is a lot of water, they’ll beep maybe once or twice, then silently die.
  • Some have batteries that cannot be replaced.
  • A few can’t be turned off except by removing the battery – just drying the contacts won’t stop the alarm.
  • Most but not all have a low battery alert – generally a chirp similar to a smoke detector.
  • Some have a lot of reviews saying that they’re not all that loud.

All will detect water somewhere in the 1/32” to 1/16” deep range. That’s actually a little oversensitive for us, as even a few drops of water from changing the speed log to the dummy plug when at anchor or a tiny leak in a hatch would set it off. But the gizmo can be set up so it’s not quite in the lowest point of the bilge (what we did – it takes a couple gallons of water to trigger the alarm) or you could glue a small strip of wood to one end of the bottom so that it would take more than just a few drops of water to sound the alarm (we don’t want a lot of nuisance alarms).

We chose the Zircon Leak Alert Electronic Water Detectors – they float, have a low battery alert, are small and are loud (from our test, I’d say they’re on a par with most smoke detectors which is plenty loud to wake us up or be heard anywhere on the boat). They can be turned off by drying the contacts and can be used again after they’ve gone off once.

Dave and I got one for each hull/bilge. Depending on your boat and bilge configuration, you might want additional water detectors near a fresh water tank or near your holding tank to tell you of problems in those areas too. They are relatively inexpensive so are a cost-effective early warning system.

We got the two-pack without batteries and bought four lithium 9v batteries (two to install immediately; two as spares):

Lithium batteries have by far the longest life in devices such as this and are worth the extra expense.

UPDATE: We recently got a couple more of a different model: The Glentronics Water Alarm reconmmended by a reader where the sensor can be placed 6 feet from the electronic alarm, which we mounted considerably higher than the sensor. This way, we can be sure that alarm won’t be flooded before we hear it.

EXTRA: Reader Chris Munson sent me an email telling how his boat had been saved once by these and another time headed off quite a bit of water damage. He gave me permission to share it here:

I’m SO glad you posted the article about bilge detectors! I have three $10 water detector alarms on my 32′ sloop; these are hardware store type alarms for home hot water heaters, dish washers, etc. They look like smoke detectors, with a sensor strip on a 36” wire. Nowhere does the word ‘Marine’ appear on the packaging. One sensor is at the ‘trigger’ water level at my main bilge pump. Should the auto-pump run, the alarm goes off. This alerted the marina staff the night my hot water heater sprang a leak and filled the bilge, syphoning the water tank as well. The other 2 are in my very isolated and sound-proof engine box. Last summer one went off while under power. Sure enough, an engine water hose had popped off, and there was 6 inches of rising hot engine raw water in the compartment. Without the alarm I would not have known the situation until the engine flooded and died. The alarm sound is like that of a smoke detector. The sensors are 2 metal studs on a plastic strip that is velcroed in place. I replace the 9 volt batteries every spring. $10 dollars each at Home Depot (see them here), usually stocked near the hot water heaters. Yes, I have 2 in my house also. They last years.

Would you know if water was filling your bilge BEFORE it got over the floorboards? The sooner you know, the better your chance of saving the boat.

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  • Helen Bell
    Posted at 22 February 2016 Reply

    We have bilge alarms on all of our bilges…as soon as they turn on the alarm sounds…we know if they r running right away

  • Kelly Beale
    Posted at 22 February 2016 Reply

    David A Beale

  • Amy Burlette
    Posted at 22 February 2016 Reply

    We are just starting to work on the mess in our bilge, we don’t have alarms (or if we do they don’t work) and the pumps don’t come on automatically when the water gets high. That’s one of the next big projects waiting in line.

  • Michael McIntosh
    Posted at 22 February 2016 Reply

    Great idea. I have on on our hot water heater at te house but had not thought about using it on the boat. Several models out there. http://www.homedepot.com/s/water%2520alarm?NCNI-5

    • The Boat Galley
      Posted at 22 February 2016 Reply

      Yep. And lots of different features. To me, one of the biggest is how loud it is and whether it will float. And to me there’s no point in getting one of the single-use ones since you can’t test it.

  • Marco Ghislanzoni
    Posted at 22 February 2016 Reply

    My two cents.

    I think it is vital, for safety and peace of mind reasons, to have a mean to test your bilge alarm from time to time. With self contained units for home use like this one (how do they cope with sea water?) that is not easy to do. With it hidden somewhere deep in the bilge, one may wonder if it is still working, or maybe you are just not hearing it, or the battery has run out without you knowing.

    Honestly I would invest, as we did, some more money to install a marine proven sealed sensor (field effect) in the bilge and run the wiring to an alarm/test panel in an accessible position, powering it from the main battery.

    While I am usually in favour of more affordable solutions when possible, I think having a reliable bilge water sensor is so important for safety related reasons that I would definitely stick with proven ones.

    Fair winds!

    • Ryan Easter
      Posted at 22 February 2016 Reply

      What did you install?

    • Marco Ghislanzoni
      Posted at 22 February 2016 Reply

      We installed a Bilge Alert system by Johnson Pump. Given the fact we have a very deep bilge, I very much like the idea that the sensor is fully sealed and doesn’t have any moving part in it (no need to go head first in the bilge to check it or do maintenance).

    • The Boat Galley
      Posted at 22 February 2016 Reply

      Marco Ghislanzoni — our bilge is very, very shallow — about 6 inches (15cm). Very easy to take it out and test. Our boat is a catamaran; different things make sense for different people.

    • Marco Ghislanzoni
      Posted at 22 February 2016 Reply

      The Boat Galley I totally appreciate that in your case it would be easier to reach and test them from time to time. On the other hand I still wonder if a sensor made for home use (where typically the noise is limited, unless you have kids around of course…) and sitting forward in one of the hulls would be loud enough the be heard while, for example, you are steaming at full throttle and are maybe sitting on the flybridge.
      If it is just for when you are at the anchor somewhere, then it could definitely do the job.

    • The Boat Galley
      Posted at 22 February 2016 Reply

      Marco Ghislanzoni If you have a larger boat or a flybrige, this is probably not for you and you might want an alarm that would repeat at the helm. But we are a small catamaran. The alarms are no more than 10 feet from the helm. We tested and they are VERY audible over the engine — louder than the oil or temp alarms. They work for us, and could work for other smaller boats. The ease of installation means that people will install them — and that is better than not getting around to installing something else. Again, different boats need different solutions.

  • Dave Paoletta
    Posted at 22 February 2016 Reply

    I have been looking for a cheap, common sense solution (my bilge is also shallow, right under the floorboards..) and once again “The Boat Galley” comes through. Thanks for doing my homework for me – I will definitely try this out!

    Dave P.
    S/V Trinacria
    Alameda, CA

  • Angie
    Posted at 24 February 2016 Reply

    This alarm saved my boat from sinking!Easy install and worth the time and money!

  • Pete
    Posted at 24 February 2016 Reply

    We use a three float switch system. The first float is at the 30mm level and has its own separate small 12 volt battery wired into the wind generator secondary charging circuit so fully charged at all times. Any water in the bulge and it alarms and also has a warning light on the cockpit dash.
    The second float which is slightly higher than the alarm float activates the 500gph bilge pump so if you have not already done something about the alarm this pump kicks in. It can also be manually switched and the pump us at a level below the 30mm level so once it kicks in the annoyingly loud alarm ceases.
    The third float is slightly higher than the second float so if all else fails the second 509gph pump kicks in.
    We also have a manual pump to back up the two electric pumps.
    If all this fails we are in deep trouble.
    Time to grab the buckets??

  • Dean
    Posted at 04 March 2016 Reply

    Great idea, we can’t hear the pump when/if it starts so this will be great as an early warning system. Has anybody come across a gas alarm that is battery operated? That would save such a lot of hassle than 12v hard wired.

  • Chris Paul
    Posted at 27 April 2016 Reply

    I used to have this exact model in the bilge, so I approve of the idea 🙂 But if there is too much water coming in, it will just drown. A quick search on Amazon will reveal models with a remote sensor, so the alarm itself can be placed even outside of the bilge, or higher than the incoming water level. Easier to hear the alarm, and it will not drown.

  • Stephanie M
    Posted at 24 June 2016 Reply

    How do you keep these from moving around in the bilge?

    • Carolyn Shearlock
      Posted at 24 June 2016 Reply

      Ours doesn’t move much (we’re on a catamaran) but you could use a loop of tape or a bit of Velcro if need be.

      • Stephanie M
        Posted at 29 June 2016 Reply

        Thanks! I don’t know what I’d do without your blog.

  • Christopher J. Melo
    Posted at 09 May 2017 Reply

    Great share. Before I could afford the real thing, a basement water alarm did duty for many years and actually gave enough warning to save the boat after a stuffing box failure halfway to Bemuda!

    • The Boat Galley
      Posted at 09 May 2017 Reply

      Good to hear (bad pun there, but I meant I’m glad you had one and it sounded when needed)!

  • Stan Morin
    Posted at 09 May 2017 Reply

    Because of a previous post, I did buy 3 for my 38 Chris Craft Catalina. I hope that I never hear them.

    • Dave Tew
      Posted at 09 May 2017 Reply

      I got two, one for next to the washing machine inn the house and one for the boat bilge.

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