What tool should I use to open the battery compartment on my computer?
Use the dedicated tool provided in the original packaging or a coin- such as a 50-cent piece- that fits perfectly into the slot to avoid warping the plastic.
How much silicone grease should be applied to the O-ring?
Apply a microscopic amount- about the size of a pinhead. The O-ring should simply be shiny and slippery. Too much lubricant will attract sand and cause leaks.
Why is it necessary to replace the O-ring each time the battery is changed?
A rubber O-ring compresses and deforms with use. Reusing a worn or pinched O-ring is the number one cause of flooding in sealed compartments.
Can metal tools be used to remove the seal?
No, you should never use sharp metal tools like a screwdriver or knife because they could scratch the plastic throat of the housing, which would compromise any future waterproofing.
Opening a waterproof instrument, whether in the confined space of a dive boat cabin or on the clean surface of a workshop table, is akin to a surgical procedure.
It was the pressure of the water that taught me, over the years and through the equipment failures of my students, that changing the battery is the most critical moment in the life of our gear.
A simple handling error, a poorly positioned O-ring, or an invisible grain of sand, and your valuable device will flood on its very first dive.
To avoid this common mishap, here's the rigorous procedure to follow step by step. The order of these steps is crucial for ensuring watertightness.
2. Step-by-Step Procedure
1. Preparing the Environment
Set up in a clean, dry, and well-lit area. Absolutely avoid dusty or sandy areas like the deck of a moving boat.
Wash and thoroughly dry your hands. Prepare your materials: a new battery, a new O-ring, silicone grease, a lint-free cloth, and the appropriate opening tool.
2. Preliminary Cleaning of the Computer
Never open an instrument that is covered in salt or sand. If the computer has recently been used for diving, rinse it with lukewarm fresh water.Carefully dry it with a clean towel before unscrewing anything. No water droplets should enter during the opening process.
3. Opening the Compartment
Unscrew the cover gently. If you use a coin, choose one that fits perfectly into the slot, such as a fifty-cent piece.
This precaution prevents damage to the plastic screw thread. Then, carefully remove the protective cap and the used battery.
4. Removing the Old Seal
Never use a sharp metal tool like a knife or screwdriver. The old seal is either on the cap or located inside the housing.
Remove it by gently pinching it with your fingers. If you scratch the plastic rim, the watertightness will never be guaranteed again underwater.
5. Cleaning the Groove
Use a clean, lint-free cloth or cotton swab to wipe the groove where the seal sits, removing any old grease.
Look for even the smallest grain of sand, hair, or salt crystal residue. The surface must be perfectly clean before installing the new seal.
6. Lubricating the New Seal
The goal is to lubricate the seal so that it slides smoothly, not to smother it with a thick layer of grease.
Apply a microscopic amount of silicone grease to your fingertips, about the size of a pinhead, and massage the seal between your thumb and index finger.The O-ring should be smooth and slippery. If you see white clumps of grease, wipe off the excess immediately because it will attract dust.
![Close-up view of clean hands handling a small black O-ring with silicone grease. In the background, an open dive computer rests on a clean microfiber work mat.] (Visual instructions: Close-up view of clean hands handling a small black O-ring with silicone grease. In the background, an open dive computer rests on a clean microfiber work mat.)
7. Installation and Closure
Insert the new battery, carefully observing the correct polarity, with the positive terminal usually facing the cover.
Place the lubricated O-ring in its groove without stretching or twisting it. Close the cover by screwing it tightly, but without excessive force.
The O-ring will naturally compress under the pressure of the cover to ensure a perfect seal.
8. Dry Leak Test
Turn on the dive computer to verify that the new battery is properly powering the device. Before taking it to great depths, perform a simple immersion test.
Submerge the dive computer in a bucket of water or a sink filled with water for a few minutes. Watch for any continuous air bubbles escaping from the cover.
Waterproof test of the dive computer in a container of fresh water
(Visual guidelines: A Mares or Suunto dive computer submerged at the bottom of a large, transparent glass container filled with clear water. No bubbles are escaping from the battery compartment.)
3. The Importance of Systematic Replacement
Some diving manuals suggest that you can clean and reuse the existing seal. This is an extremely risky choice.
A new O-ring costs less than three euros, while a flooded dive computer represents a loss of several hundred euros.
For each opening, purchase a complete kit including the battery and its dedicated sealing ring. To identify the correct battery model for your device, consult our complete guide to dive computer batteries.
4. Training for Safe Diving
Technical proficiency with your equipment is essential for diving safely. Simple actions can save computers and dives.
To improve your maintenance skills and understand the theory of decompression, discover our interactive modules on AquaExposure Training.
