Features May 15, 2001 Issue

Aqua Vigil Alarm Is Simple but Quirky

Nothing is scarier than seeing water coming into your boat, the bilges overflowing, and the floorboards floating. If you're not aboard to see the spectacle, you'll be safe — but it might be curtains for your boat.

To prevent these catastrophes, we employ all manner of backup systems—electric bilge pumps, switches, and alarms, usually dependent on the boat's 12-volt batteries. (The simplest alarm system we've heard of was that of the sailor who slept with the floorboards up and his hand dangling into the bilge.) 

The Water Sensor is a conductivity-type
switch designed to alert you to high water.
Unfortunately, the alarm sound slowly fades
away as the contacts dry, and both oil and
soap trigger the alarm — a nuisance.

Moving up the complexity scale, there are indicator lights available for showing that the pumps are on and separate bilge switches that turn on an audible and visual alarm when there is too much water in the bilge.

Even with all these ways of dealing with water intrusion, we’ve been on some boats where our first indication of a problem was floating floorboards. At that point you have an emergency on your hands, because the higher the water rises, the greater the pressure mounts to force water in, and the harder it is to find the source of the leak.

Obviously, the sooner you know that water is rising in your bilge, the better your chances of success in dealing with it.

In our January 1, 1996 issue we looked at a simple device called the Water Detector, made by Zircon of Campbell California. Sold in hardware stores for home use, it's meant to be placed on its back or side in an area likely to suffer a leak (for example at the base of a hot-water heater, or in a basement sump). It's activated when water closes a circuit via two exposed wires. It floats, but is not waterproof. It operates on a 9-volt battery, which will power a continuous alarm for 72 hours. We noted that it could be useful as a bilge alarm, and could also warn of a plugged icebox drain.

Now enter the Aqua Vigil high-water warning device from Aqua Vigil in Florida.

A Conductivity-type Switch
The Aqua Vigil alarm has two parts—the electronics box and the remote sensor. The bone-color ABS plastic electronics box is 5.8"H x 3.6"W x 1.3"D. The device is designed for vertical mounting (supplied with two mounting screws), but it can be mounted at any angle. Assuming vertical mounting, there's a mini-phono jack on the bottom of the Aqua Vigil for the sensor to plug in to. Centered on the unit’s front is an 85 dB piezo alarm, which emits a 3.5 kHz pulsing tone at a four-times-per-second rate. Like the Zircon Water Detector it uses an internal 9-volt battery (not included) instead of relying on the boat’s 12-volt system for power.

The sensor mounts in the bilge above the normal water height with one self-tapping screw (supplied). A 6-foot cable connects the sensor to the electronics box with a mini-phono plug. The sensor node looks like a standard RCA phono jack cut off just into the strain relief. The sensor itself consists of two concentric metal rings. When water bridges the gap between the rings, it switches on the alarm.

The electronics box is not sealed against moisture. Care should be taken to mount it in a dry location, while still keeping it within 6 feet of the sensor’s location in the bilge. For a longer distance, you can separately purchase 10-foot extension cables (p/n EXT-10 for $5) for the Aqua Vigil that may be ganged for greater distances. There's also an option to have two sensors connected to one electronics box (p/n DP-2KT $10) for monitoring two bilge areas. Although we have not tested this, we have some concerns with sensor corrosion, especially in the miserable bilge environment.

The Aqua Vigil does produce an alarm when the sensor comes into contact with water. With no water on the sensor, our current meter showed that the consumption from the 9V battery was less than one micro-amp. The manufacturer recommends changing the battery once a year.

As a quick test of the Aqua Vigil, we put the sensor into tap water and let the alarm sound for 200 hours. At the end of this time, the battery voltage was close to 8V. Using the battery curves from Duracell’s web site and a 5V battery cutoff, we estimate that the Aqua Vigil should continue beeping for perhaps 900 hours (more than a month).

Due to the simple design of the sensor and electronics, we found some quirks in the Aqua Vigil’s operation. First, the sensor/electronics combination doesn’t have a threshold before sounding the alarm. For example, a thin film of water creates a tiny chirp whereas immersing the sensor in water creates the full-volume alarm. Likewise, as the sensor dries, the alarm gradually fades out over many minutes. To shut it down more quickly, you can either dry the sensor’s surface or pull the sensor plug from the electronics box.

Second, we found that oil in the bilge water can foul the sensor so that it can’t sense the conductivity of the water. To cure this, you need to wipe off the sensor’s surface until it's clean and then test the sensor. Testing is easy: Put some water or saliva on your finger and touch it to the sensor’s surface.

Third, we found that if the bilge water has soap or detergent mixed in with it, the soap bubbles can stick to the sensor surface and energize the alarm. Again, cleaning the sensor surface alleviates this problem.

If we were going to install the Aqua Vigil in our boat, we would mount it as high in the bilge as possible, as a last-chance alarm, and not use it for everyday high-water detection. Mounting it high up will minimize sensor fouling and corrosion. Also, make sure to mount the electronics box so that others in the marina can hear the alarm outside your locked-up boat.

The Aqua Vigil comes with a one-year warranty and is available from the manufacturer for $59.95 plus shipping and handling.


Contacts- Aqua Vigil Corp., PO Box 3334, Clearwater, FL 33767-8334, 800/739-9888, 727/461-9600, www.floridarep.com. Zircon Corp., 1580 Dell Ave., Campbell, CA 95008, 408/866-8600, www.zircon.com.

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