FCOA makes an effort to make diving accessible for everybody. When it comes to scuba diving, we need technical equipment. By knowing how to do simple repairs ourselves, we can save time and money getting things fixed. By knowing how to test secondhand equipment, we can buy gear at a fraction of the new price.
For all equipment, keep in mind that salt crystals deteriorate materials. Your best bet is to wash your gear right after the dive before the salt starts crystallizing. It's best to submerge the equipment in fresh water and leave it there for a while. The colder the water, the longer it takes for salt crystals to dissolved; 3 to 5 minutes should do it.
Another factor that deteriorates dive equipment is sunlight, so dry your equipment in a shaded and cool area.
PERSONAL TOOLS AND PARTS
Recommended for scuba divers to keep in their gear bags.
Dynamic Seals vs. Static O-Rings
There are two kinds of O-rings in your scuba equipment:
Static O-rings: These are not subject to wear and tear. They simply create a seal, and if left undisturbed, they can maintain that seal for a very long time. The O-rings that seal between the first stage and the hoses connected to it are static.
Because they are not in contact with moving parts, they hardly ever leak.
Dynamic O-rings: These are in contact with moving parts, so they often wear out, start leaking, and require regular replacement. It is good practice to carry spare dynamic O-rings along with the tools needed to replace them.
Common Dynamic O-Rings to Carry:
- Scuba tank O-rings: When the yoke overtightened, the O-ring can get damage and start leaking. They are also easily lost, especially if the yoke is opened while there is still residual air in the hoses.
- Swivel Pin O-Rings: (or a complete swivel pin for your SPG).
- Second Stage to Low-Pressure Hose O-Ring: Since the second stage can rotate, this O-ring is subject to wear and tear.
- Inflator Hose Quick-Disconnect O-Ring: Exposed to wear and tear every time you connect or disconnect the inflator.
- Internal Inflator Button O-Rings: Exposed to friction every time the buttons are pressed.
TOOLS
The tools required to maintain scuba gear vary by brand. It is best to use spanners (wrenches) of the exact required size rather than an adjustable wrench, as adjustable wrenches have a tendency to slip, damaging and rounding off the edges of the nuts.
Recommended Tools to keep in Your Bag:
- A dental pick to remove O-rings (for example, from the inside of your inflator).
- The two spanners needed to separate the SPG from the hose (you may need hot water to soften and remove the rubber boot surrounding the SPG).
- The two spanners needed to separate the second stage from the low-pressure hose.
- The Allen key needed to remove a DIN insert from a scuba tank valve.
- The specific tools needed to open your inflator valve.
REGULATORS
Evaluating Secondhand Regulators
Before purchasing a secondhand regulator, perform the following tests:
- Suction Test: Before connecting the regulator to a tank, suck gently through the mouthpiece and listen/feel for air leaks.
- Pressure Test: Connect the regulator to a tank pressurized to 200 bar and listen for air leaks. Better yet, apply soapy water with a sponge to see if bubbles form around leaks, or submerge the pressurized regulator in fresh water to observe any escaping bubbles.
- Breathing Test: Breathe from both the primary and secondary (octopus) regulators to ensure breathing feels effortless. It is normal for regulators to make a loud bussing or humming sound when breathed above water. This is caused by the diaphragm vibrating; once underwater, ambient water pressure stabilizes the diaphragm and stops the vibration.
Reasons a Regulator Might Free-Flow
- A grain of sand is preventing
the demand valve seat/lever from closing completely. Press the purge button while tapping the demand valve gently, or rinse the demand valve with fresh water while pressing the purge button (without air pressure connected).
- A salt crystal is blocking the valve seat/lever. Submerge the regulator in fresh water to dissolve the salt.
- A calcium buildup is preventing the lever from closing.
Submerge the affected part in vinegar for 5 minutes to dissolve the calcium.
- Altered Spring Tension: Impact or wear has altered the spring tension. Open the regulator housing and adjust the nut that regulates spring tension. .
- Worn First-Stage Seat: A worn high-pressure/intermediate seat causes the intermediate pressure (normally around 10 bar) to creep slowly up to 11, 12, or 13+ bar. The second stage is designed to vent this excess pressure. If this occurs, the second stage is functioning correctly—it is simply receiving excessive pressure. The seat in the first stage must be replaced. You can confirm this by attaching an intermediate pressure gauge to the first stage. On some first stages, the Teflon seat can be flipped over to use the unmarred side.
- Debris in First Stage: Salt or calcium deposits inside the first stage can also cause intermediate pressure creep. Before attempting a full overhaul, disconnect the hoses, soak the first stage in vinegar for 5 minutes, rinse in fresh water for 5 minutes, blow out all residual water, and reattach the hoses to check if the issue is resolved.
Replacing SPG Swivels and Second-Stage O-Rings
Because SPGs and second stages rotate, their seals use dynamic O-rings that require periodic replacement. To replace the SPG O-ring, remove the gauge from its rubber boot. Heating the boot in hot water softens the rubber, making removal easier. Always use exact-fitting tools to avoid scratching sealing surfaces, and use a dental pick to remove old O-rings carefully.
BCDs (BUOYANCY CONTROL DEVICES)
Tips When Buying Secondhand
- Inflate the BCD completely and check that it holds pressure over time.
- Overinflate the BCD until the overpressure relief valve (OPRV) opens to ensure it vents and reseals properly.
-
Ensure the inflator nipple matches your low-pressure inflator hose; while most use a standard fitting, proprietary non-standard fittings exist.
-
If the inflator hose assembly tears away from the fabric jacket, it is generally not worth repairing, as most fabric patches on bladder materials fail quickly under pressure.
Common BCD Repairs
- Self-Inflating BCD: Check if the inflation button is sticking. Soaking the power inflator assembly in vinegar will dissolve calcium deposits causing the valve to stick. If soaking fails, disassemble the inflator. Many power inflators use standard Schrader valves (similar to car tire valves). If so, replace the valve core.
- Early-Venting OPRV: If an overpressure valve releases too early, unscrew the housing, stretch the internal spring slightly, and reassemble it to increase spring tension.
- Pinhole Leaks: Small punctures or tears in the fabric/bladder can be sealed using specialized flexible adhesives such as Aquaseal.
SCUBA TANKS (CYLINDERS)
Inspection and Testing
In most countries, scuba tanks must undergo hydrostatic testing every 5 years
(and annual visual inspections). After a hydrostatic test, the testing date is stamped onto the tank neck.
To find affordable testing facilities, inquire where local industrial gas suppliers or hospitals send their oxygen cylinders, as these also require 5-year hydrostatic retests. While dive centers offer tank testing services, they typically charge a fee to handle valve removal, preparation, and transport.
To check for leaks around the valve or neck seal, spray the area with soapy water and watch for bubbles, or submerge the pressurized tank valve underwater.
Tank Materials
Tanks are primarily manufactured from steel, aluminum, or carbon fiber composite:
Steel: Heavier out of the water, which allows divers to carry less lead weight on their weight belts. Steel can corrode (rust) internally and externally if exposed to moisture; while rust should be addressed promptly, steel cylinders are extremely durable and offer long service lives as long as they pass periodic inspections.
Aluminum and Carbon Fiber: Lighter alternatives, but require different handling and weighting strategies.
CRITICAL WARNING
Valve-to-Cylinder Mismatch:
When purchasing a replacement tank valve, verify that the thread specification matches the cylinder neck exactly (e.g., metric vs. imperial threads). Installing an incorrect valve can result in the valve stripping out under high pressure, causing a fatal explosion or severe injury.
.
SURFACE MARKER BUOYS (SMBs)
To test an SMB for leaks, fill it with water and hang it up to check for drips. If water escapes, air will escape during use.
DIVE COMPUTERS Common Issues & Maintenance
- Pressure Sensor Failure: The depth sensor interprets ambient pressure. If it fails, the computer will display either no depth reading or an inaccurate depth.
- O-Ring Seal Leaks After Battery Replacement: Improperly seated battery compartment O-rings can flood the unit. Professional dive shops test battery replacements in a dry pressure chamber or a water-filled chamber under vacuum. Under vacuum, escaping bubbles indicate an compromised seal, allowing the technician to open, dry, and re-seal the computer before water causes damage. Once salt water enters an electronic dive computer, the device is usually unrecoverable.
- Software & Algorithm Errors: Maintain proficiency with manual dive tables or planners. Cross-checking your dive profile allows you to spot erroneous computer readings during a dive.
- Incorrect Gas/Altitude Settings: Verify that the computer is set to the correct mode (e.g., Air, Nitrox mix percentage, or Altitude mode), as incorrect settings directly alter your No-Decompression Limit (NDL). Always consult the user manual. .
- Freedive Mode vs. Scuba Mode: Using a dive computer in Scuba mode while freediving will trigger rapid-ascent warnings and register missed safety stops, which may lock the computer out of operation for 24 to 48 hours.
- Purchasing Secondhand: Request a video from the seller showing the computer operating underwater at depth; a short video verifying sensor responsiveness provides valuable confirmation of functionality.
UNDERWATER CAMERAS
- Housing Pressure Test: Test an underwater housing without the camera inside first. Place dry tissue paper inside the housing, seal it, take it on a test dive, and check that the tissue remains completely dry.
- Rinsing: Soak camera housings in fresh water immediately after exiting salt water. Do not allow salt water to dry on the buttons or O-rings, as salt crystallization damages the mechanical seals.
OXYGEN CLEANLINESS
"Oxygen Clean" refers to equipment or components that have been thoroughly processed to remove organic contaminants (such as oils, grease, dust, and particulate matter) that could ignite or explode when exposed to high partial pressures of oxygen.
Equipment used with enriched air Nitrox containing up to 40%–50% oxygen generally utilizes standard scuba cleaning protocols (depending on local regulations). However, any equipment exposed to gas mixtures exceeding 50% oxygen must be strictly oxygen cleaned and prepared with oxygen-compatible lubricants (e.g., Christo-Lube).
