Do It Yourself Soda Water Carbonation

Daniel's Soda-Water Machine

I drink a lot of carbonated water.   I enjoy the fiz and the bubbles bouncing off of my tongue.  Don't judge me, it is the way that I am.

What I don't like is filling our Blue Box Recycle bins with plastic bottles or aluminum cans after a binge night of hitting the ol' bubbly.  So.. I decided to make my own bubbly and reuse PET bottles.  Poly-Ethylene Teraphthalate, those clear or green, rarely blue plastic bottle that soft drinks are sold in.

Now one can buy a machine to make soda water, but these tend to require non-standard CO2 cartridges or tanks that are expensive to buy or refill, or worse.. disposable.  So I decided to make.

This is a practical DIY item, similar to my Homemade Geiger Counter from January 2010.

This is my new Water Carbonator.  I slowly gathered the requisite parts over the last year.  Bought the 7 1/2 lb CO2 bottle last year, then the regulator, then the food grade beverage tubing, ball lock connector and finally the ball lock connector -> PET bottle cap adapter.

Caution to others: do not use reinforced tubing.  You really want the tubing to be the weak component.  In the event of a defective regulator dumping 900 PSI into your line, a split tubing line is a non-event in the safety world, whereas an exploding PET bottle will effectively redefine for you the words 'exciting' and 'shrapnel'.

I have seen others where the maker used a tire chuck at the end of the tubing instead of a ball lock connector and set tire fill Schraeder valves into PET bottle caps.  Problem with that is the black rubber seal bits breakdown and can end up in your water (ew).  Also, the tire air chuck and valve stem are not made of food grade metals.. also (ew).

Ambient air == no fun, squeeze it out!

The ball lock connector is the standard for connecting a CO2 supply to beverages, what was tough was finding an adapter to connect a PET bottle to a ball lock connector.

Fortunately a company in the U.S. makes just such an adapter. Search the web for Carbonator Cap PET and you should find any number of online suppliers willing to sell you one for anywhere between $12 and $20.  The come in red or blue.  You usually do not have a choice. I like the blue.

To use: Fill a PET bottle with dammed cold water.  You can use kinda cold water, but you will fail at getting much fiz.  You can take my word for it or Le Chateleir's Principal.  "When a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure the equilibrium shifts to counter the imposed change and a new equilibrium is established".

Remember in school when you asked your Physic's prof why you needed to learn this stuff and when would you ever need it?  This is why and magically also the when.  Water down at near freezing will absorb CO2 at the most successful rate.  I caution that if using 0 degrees Celsius water that you use CO2 pressure at less PSI then warmer water levels since the PET bottle pressure will increase dramatically should that bottle be left on a room temp counter.

Carrying on..  squeeze the bottle to force out the ambient air mixture as nitrogen and oxygen will interfere with our process.   Attach the PET bottle adapter and give the bottle one last squeeze as you press down on the valve on the adapter to 'burp' out any remaining air.

CO2 absorption

Now the FUN!  Connect the ball lock connector to the PET adapter and open your CO2 supply line.  I have set my regulator here to 25 PSI.  Others recommended 10 PSI and others 40.  I figured 25 was a good starting point.  As the pressurized CO2 is applied, the bottle immediately inflates and a shaking motion back and forth allows the water to surface contact the CO2 and absorbs it.

How much CO2 can be absorbed is limited by Henry's Law.  That law states: "At a constant temp, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid".  The more pressure, the more will be absorbed.

Continue to shake for 30 seconds.. rest for 30 shake.. for a couple of minutes.  There is no set routine, really damn cold water will take on CO2 faster than cold and surface area is a factor.  The nice thing about this set up is that I can deliver constant CO2 pressure to the solution whereas the air chuck guys need to keep topping up their bottles during the shake and dance phase.  DO NOT allow your solution to flow up your line.  That would be bad form as you would contaminate your line with your beverage.  Not a huge deal when just carbonating water, but messy when you start to make your own fizzy lemonade or gin :)

Let the bottle rest for a bit under pressure, and then release the ball lock connector.  You need not close the regulator exit barrel valve (the small red lever pointing straight down in the open position in the pics above) prior to releasing the ball lock, the ball lock will maintain line pressure all by itself.  But if you are done for the day, then close your main tank valve.

Put in the fridge with the PET bottle adapter in place for an hour or so to complete the carbonation and then remove the PET bottle adapter and replace the PET bottle cap, toss back in the fridge.  That's it.  Enjoy your bubbly!