CO₂ Setup

Gas Path

Check Valve

This section covers preparing the keg, connecting the CO₂ system, and setting up dispensing.

Choosing Your CO₂ Tank

Before you begin setup, you’ll need to choose a CO₂ tank size. Here’s a comparison to help you decide:

CO₂ Tank Comparison

Choose the right tank size for your needs and usage patterns.

Feature	SodaStream Tank	5 lb Tank	10 lb Tank	20 lb Tank
Capacity	60L (14.5 oz)	~320L	~640L	~1280L
Initial Cost	$30-40	$60-80 (+ tank)	$80-120 (+ tank)	$100-150 (+ tank)
Refill Cost	$15-20 exchange	$15-25 refill	$20-35 refill	$25-45 refill
Refill Frequency	Every 2-4 weeks	Every 2-4 months	Every 4-8 months	Every 6-12 months
Portability	High	Medium	Low	Low
Best For	Beginners, small spaces, light use	Most home users, moderate consumption	Heavy users, families, stationary setups	Heavy users, permanent installations

SodaStream Tank 60L (14.5 oz)

Initial: $30-40

Refill: $15-20 exchange

Frequency: Every 2-4 weeks

Portability: High

✅ Pros:

• Easy to find exchanges
• Compact size
• No special adapters for standard use

❌ Cons:

• Higher cost per liter
• Requires TR21-4 adapter for keg use
• Frequent exchanges

Best for: Beginners, small spaces, light use

5 lb Tank ~320L

Initial: $60-80 (+ tank)

Refill: $15-25 refill

Frequency: Every 2-4 months

Portability: Medium

✅ Pros:

• Good balance of size/capacity
• Standard regulator fits
• Easy to transport for refills

❌ Cons:

• Need to find a gas supplier
• Takes up fridge space if inside

Best for: Most home users, moderate consumption

10 lb Tank ~640L

Initial: $80-120 (+ tank)

Refill: $20-35 refill

Frequency: Every 4-8 months

Portability: Low

✅ Pros:

• Fewer refill trips
• Lower cost per liter
• Can stay outside fridge

❌ Cons:

• Heavy (~25 lbs full)
• Harder to transport
• Takes more space

Best for: Heavy users, families, stationary setups

20 lb Tank ~1280L

Initial: $100-150 (+ tank)

Refill: $25-45 refill

Frequency: Every 6-12 months

Portability: Low

✅ Pros:

• Best cost per liter
• Rarely need refills
• Commercial-grade reliability

❌ Cons:

• Very heavy (~50 lbs full)
• Must stay outside fridge
• Harder to exchange

Best for: Heavy users, permanent installations

Step 1: Prepare the Keg

1. Clean the Keg. Ensure the keg is clean and sanitized. See Best Practices for detailed cleaning instructions.
2. Attach the Soda Carbonator Lid to the keg as per instructions.
3. Ensure the keg is empty and the lid is sealed securely.

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Step 2: Set Up the CO₂ System

1. Use food-grade tubing to connect the CO₂ regulator to a one-way check valve. Arrow should face the keg. You want to prevent water flow back toward the CO₂ tank, especially for when you swap tanks. For information on tubing sizes, see the Water Line Setup guide.
2. Use tubing to connect the check valve to the gas quick-disconnect fitting.
3. Attach the gas quick-disconnect to the gas post on the keg. Press hard until it clicks.
4. Attach the CO₂ regulator to your CO₂ tank.
5. Set CO₂ regulator to about 40 PSI
6. Vent out all the oxygen by pulling the vent pin on the keg lid. Let the CO₂ fill the keg and vent a few times until only CO₂ remains. This prevents oxidation of trace elements in the water. Stop venting when water comes out, you’re just trying to vent air.

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Aside: Chemistry and Effects of Atmospheric Gases

When atmospheric air is present in the keg, several chemical processes can occur that affect water quality:

Carbonic acid formation: Carbonic acid forms when CO₂ dissolves in water and reacts with it (CO₂ + H₂O → H₂CO₃). The presence of oxygen doesn’t significantly accelerate this reaction, but oxygen can cause oxidation reactions that lead to off-flavors and unwanted taste in the water.

Chemistry of off-flavors: Dissolved oxygen can oxidize trace organic compounds in water, producing aldehydes and ketones that create stale, flat, or cardboard-like tastes. Oxygen can also react with any lipids or flavor compounds present, degrading them into compounds with unpleasant odors and flavors. Additionally, oxygen exposure can cause carbonation to dissipate more rapidly, resulting in a flatter drink. The acidic environment created by dissolved CO₂ (lower pH) helps inhibit these oxidation reactions, which is why purging with CO₂ preserves water quality.

Other atmospheric gases: Atmospheric air contains about 78% nitrogen (N₂), 21% oxygen, and 1% other gases including argon and trace compounds. Nitrogen is relatively inert and has low solubility in water, so it doesn’t directly cause chemical reactions or off-flavors. However, dissolved nitrogen can compete with CO₂ for space in the water, potentially reducing carbonation levels and affecting the equilibrium of dissolved gases. The presence of multiple dissolved gases can also influence pH and total alkalinity. By purging with pure CO₂, you ensure maximum carbonation efficiency and prevent any potential interactions between different dissolved gases. Trace amounts of other atmospheric compounds (like volatile organic compounds or pollutants) could also dissolve and affect water quality, though this is typically minimal in clean water systems.

Health effects of carbonic acid: Carbonic acid is a weak acid naturally present in all carbonated beverages. For most people, moderate consumption of plain carbonated water is safe. The mild acidity has minimal impact on dental enamel compared to stronger acids or sugary drinks. Some individuals with sensitive digestive systems may experience bloating or gas due to the release of CO₂ in the stomach. Plain carbonated water does not negatively impact bone health. Overall, carbonic acid in carbonated water poses minimal health risks when consumed in moderation. The author consumes unflavored carbonated water constantly and brings it up to his dentist, who thinks it’s a little weird to drink so much carbonated water, but doesn’t observe any negative health impacts.

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Step 3: Fill and Carbonate

1. Open the refrigerator line and allow the water to fill the keg. Eventually it will stop filling.
2. If needed, vent any remaining air by pulling the vent pin. Stop if water comes out.

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Step 4: Set Up Dispensing

1. Connect tubing to a liquid quick disconnect and attach it to a valve.
2. Connect another tube between valve and the tap faucet.
3. Attach the liquid quick-disconnect to the liquid post on the keg. Press hard until it clicks
4. Dispense some water to ensure the water system is working. It probably won’t be sparkling yet

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Step 5: Wait for Carbonation

• It can take some time for the CO₂ to dissolve in a full keg
• If the water is colder, it will carbonate faster.
• Be patient - the first carbonation cycle may take several hours

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Water Temperature vs Carbonation Speed

Water temperature has a significant impact on carbonation speed and efficiency:

CO₂ Solubility: CO₂ dissolves more readily in colder water. At approximately 4°C (39°F), CO₂ solubility is at its peak, allowing more gas to dissolve into the water. As temperature increases, CO₂ solubility decreases, meaning warmer water holds less dissolved CO₂.

Carbonation Speed: Colder water not only holds more CO₂ but also absorbs it faster during the carbonation process. Keeping your system in a refrigerator ensures both faster initial carbonation and better retention of carbonation over time.

Practical Impact: For optimal carbonation, maintain water temperatures around 35-40°F (2-4°C). Warmer water will take longer to carbonate and may lose carbonation more quickly, as the gas escapes more readily at higher temperatures.

This is one of the key reasons why housing your system in a refrigerator is recommended; it keeps the water cold for both faster carbonation and better carbonation retention.

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Preferred CO₂ Pressure

40 PSI gives the best bubbles in my opinion, but you can vary the pressure somewhat to suit your taste. Higher pressure will result in more carbonation and fizzier water, while lower pressure will produce lighter carbonation. Experiment to find your preferred level.

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Troubleshooting

For a complete list of troubleshooting tips, including carbonation issues and leaks, see the Best Practices page.

Next Steps

Once everything is connected and carbonating, see Refrigerator and Cooling for tips on housing your system.