How to Safely Reuse and Repurpose Old Scuba Diving Tanks

Diving deep into the mysteries of the underwater world requires some expensive gear, with scuba tanks being one of the most costly.

But if your aluminum or steel tanks expire, you may wonder how to reuse them.

If scuba tanks expire, don’t just send them away to a junkyard without a closer optimistic look. With some strategic repurposing and TLC, you can give those old cylinders a new life above water.

Let’s see how.

How To Reuse Old Scuba Tanks

Scuba demands robust, high-pressure gas cylinders, typically made of aluminum or steel. While cheaper, aluminum tanks aren’t as enduring as their steel counterparts. These hardy tubes are built to handle years of adventure but ultimately get retired after about 5-15 years.

Scuba tank lifespan depends on factors like usage frequency, corrosion, and accidents. Once the hydrostatic testing date stamps expire, shops refuse fills for liability reasons.

But just because tanks won’t go diving again doesn’t mean their glory days are over. With proper precautions, expired tanks can be repurposed for:

The main factors are ensuring valves, O-rings, and fittings are in good condition and following all safety steps when modifying, pressurizing, or cutting tanks. Always proceed with care – because mishandling can cause explosions.

Inspect The Old Tanks Before Reuse

Before sending an old tank on its next mission, conduct a thorough assessment:

Only proceed if your tank passes inspection. Compromised cylinders can explode under pressure. Consult a professional if uncertain. If you think the tank is on the verge of getting damaged, then you can use it for reuse purposes.

Cleaning and Prepping The Tanks for Reuse

A deep clean is required before sending retired tanks on new adventures:

• Remove all valves and fittings – Unscrew and inspect any attached parts. Replace damaged O-rings, washers, etc.
• Rinse out loose debris – Shake out all dirt, sand and residue.
• Use an alkaline cleaner – Let soak for 15-20 minutes to remove grease, oil and grime.
• Rinse multiple times – Flush the interior until the water runs clear. Vinegar or citric acid helps remove deposits.
• Dry completely – Air dry fully or purge remaining moisture with clean compressed air.
• Reattach parts – Confirm valves and fittings seal properly before pressurizing.
• Add new label – Cover old certifications with a “Non-DOT Approved” warning.

Proper cleaning is essential for measuring the ability of the tank to be reused.

Cutting Tanks Open Safely

Many repurposing projects require accessing a tank’s interior by cutting it open. This is extremely dangerous and should only be attempted with proper precautions:

1. Fully purge the tank – Remove all gas by opening the valve underwater until the bubbles stop.
2. Research proper cutting procedures – Consult experienced welders on the safest torch, blade or saw type.
3. Mark cutting lines precisely – Use a straightedge and soapstone.
4. Clamp the tank securely – Use a sturdy vise or jig for stability.
5. Wear safety gear – Face shield, ear protection, fire-resistant clothes, etc. Have an ABC extinguisher nearby.
6. Make relief cuts first – Lightly score along cut lines to relieve internal stresses.
7. Cut slowly and cautiously – Apply heat/force gradually, watching for issues. Stop immediately if anything seems unsafe.
8. Use an exhaust system – Position a hose near cut point to evacuate hot fumes.
9. Inspect carefully afterwards – Allow cooling, then thoroughly check for cracks or defects.

Rushing the cut or using the wrong tools can cause explosions and serious harm. Consult an experienced professional if you are uncertain about it.

Modifying Valves and Fittings

Valves and fittings play a critical safety role by controlling gas flow. When repurposing tanks, you may need to modify or replace these parts. This requires care to prevent leaks.

Removing Old Parts

• Use penetrating oil to loosen stuck threads.
• Clamp the tank securely to avoid rotation.
• Grip valve bodies, not just stems.
• Unscrew slowly with a properly sized wrench.
• Detach any O-rings, washers or gaskets for replacement.
• Use a valve wrench if unable to grip adequately.
• Avoid bending or damaging valve stems.

Some Exciting Repurposing Ideas for Old Tanks

With some creativity, old scuba cylinders can be prepped for exciting second purpose. Here are some of these potential projects:

1. High-Pressure Gas Storage

Devalved tanks make inexpensive cylinders for:

• Recharging pneumatic tools
• Filling paintball hoppers
• Storing compressed gases
• Charging fire extinguishers
• Supplying kegerators or soda fountains

Use proper CGA fittings and follow all pressurization limits.

2. Air Cannon or Spud Gun

Seal off one end and install a quick exhaust valve to build:

• Powerful air cannons for launching projectiles
• High-powered potato guns for distant spud shooting

Use extreme caution and limit pressurization to 100 psi or less.

3. Portable Air Tank

Cut a tank horizontally and weld on caps to create:

• A portable tank for off-road trailers, RVs, overlanding, etc.
• An emergency air supply for filling tires
• A pony bottle for short secondary dives

Use a regulator and keep volume under 30 cubic ft.

4. Pneumatic Tool Air Reservoir

Use scuba tanks to store compressed air for:

• Powering pneumatic nail guns, impact wrenches, etc.
• Supplying airbrush or HVLP spray painting
• Running air-powered ratchets, sanders, and tools

Install safety valves and use regulators rated for tool use.

With creativity and proper precautions, retired scuba tanks can be prepped for exciting second usage! Just follow all safety protocols when pressurizing high-pressure cylinders, and consult experienced technicians anytime tension strikes.

Step-By-Step Instructions for Common Projects

Once you’ve assessed a used scuba tank and deemed it suitable for reuse, there are some great DIY projects to take on. Here are detailed steps for the most popular repurposing ideas:

Converting Tanks into High-Pressure Air/Gas Storage

Here’s how to safely convert old scuba tanks into vessels for storing compressed air, gases, or CO2:

Step 1: Tank Prep

1. Clean thoroughly and let dry completely
2. Remove all valves and fittings
3. Sand and repaint the exterior if desired
4. Label as “Non-DOT” if previously used for diving

Step 2: Install New Valve

1. Research needed CGA valve for gas type (ex: CGA-320 for CO2)
2. Apply thread sealant to valve threads
3. Screw in the CGA valve and tighten to 85 ft-lbs torque

Step 3: Attach Fittings

1. Install outlet ball valve for gas flow control
2. Add bleeder valve on the opposite side for purging
3. Use Teflon tape on all male NPT threads
4. Wrench tighten fittings to 40 ft-lbs max torque

Step 4: Pressure Test

1. Seal valve openings with plugs/caps
2. Slowly pressurize tank to max working pressure
3. Check for leaks at valves or fittings using soapy water
4. Depressurize and reseal if any leaks are found

Once converted, the tank is ready for securely storing compressed air, inert gases, CO2, or other approved media, staying at or below the tank’s rated pressure capacity.

Building an Air Cannon from a Scuba Tank

Here are the steps to follow to construct a pneumatic air cannon from a used scuba cylinder:

Step 1: Tank Preparation

1. Clean the tank thoroughly and let it dry completely
2. Cut tank to desired barrel length
3. Deburr and smooth cut edges to prevent damage
4. Install threaded end caps on both ends using thread sealant

Step 2: Release Valve Installation

1. Drill and tap hole in the rear end cap for valve threads
2. Apply thread sealant and install high flow ball valve or quick release
3. Orient valve to allow rapid exhausting of tank air

Step 3: Muzzle Attachment

1. Drill holes in the front end cap for muzzle mount bolts
2. Cut PVC pipe to size and chamfer edge for muzzle
3. Attach muzzle section using gasket and bolts through end cap

Step 4: Pressurization and Testing

1. Add air fill valve to allow tank charging
2. Slowly pressurize to no more than 100 psi
3. Check for leaks using soapy water
4. Verify stable muzzle mount and proper valve function

The air cannon is now ready for launching soft projectiles! Always observe safety protocols when firing.

Making a Portable Low-Pressure Air Tank

Here’s how to convert old scuba tanks into portable air tanks for inflating tires or powering low-pressure pneumatic tools:

Step 1: Tank Preparation

1. Thoroughly clean and dry the tank
2. Measure and mark cut lines to reduce tank size
3. Clamp the tank securely and cut along marked lines
4. Smooth cut edges and remove any sharp burrs

Step 2: End Caps

1. Select end caps based on tank diameter
2. Apply sealant to cap threads and screw into both ends
3. Torque caps to 40 ft-lbs for aluminum, 90 ft-lbs for steel

Step 3: Fittings and Valves

1. Install high flow ball valve for inflating and bleeder valve for purging
2. Add pressure regulator or tire inflator fitting
3. Use thread sealant on all fittings and tighten securely

Step 4: Leak Check

1. Pressurize the tank to no more than 125 psi
2. Spray soapy water on caps and fittings
3. Ensure no leaks before filling the tank with air

The portable air tank is now ready for use. Follow safe pressures and drain after each use. Proper handling is critical to avoid explosions.

Building a Scuba Tank Air Pig

Here are the steps for constructing a high-capacity air pig from a used scuba tank for powering pneumatic tools:

Step 1: Tank Preparation

1. Clean and dry the tank completely
2. Measure and mark cut lines 12-18” from one end
3. Clamp the tank and make relief cuts before full cut
4. Grind smooth and deburr cut edge

Step 2: Breather Tube Installation

1. Drill holes in both ends to fit breather tube
2. Cut copper tube to fit between holes
3. Braze tube to curved ends for flexible connection

Step 3: End Cap and Fittings

1. Install 2” NPT end cap on cut end using sealant
2. Add 1” ball valve for air flow control
3. Install air quick connect fitting for tool hookup

Step 4: Leak Check

1. Pressurize tank to 150 psi max
2. Spray soapy water on end cap and fittings
3. Ensure no leaks before use

The air pig is ready for powering pneumatic tools. Just follow all safety protocols when pressurizing.

Recommended Read: How Long Does a Scuba Tank Last?

Essential Safety Tips for All Tank Projects

When repurposing old scuba cylinders, safety is paramount. Follow these tips to avoid accidents:

It’s also wise to have tanks re-inspected every few years, even for low pressure applications. Never take shortcuts when handling and transporting high-pressure gas cylinders.

Final Words

With some strategic TLC and proper precautions, expired scuba tanks can be repurposed for exciting projects rather than throwing it to the junkyard.

Just be sure to follow all necessary safety steps when working with high-pressure cylinders, and tap experienced professionals for guidance whenever unsure. Your retired diving buddies still have plenty of adventures left in them.