Built It: DIY Sodastream - Fail

Spoiler alert: This didn't work.

What if, instead of buying a commercial soda maker, you could just swap out the top on an existing soda bottle and pressurize that? And what if you could rescue a 2-liter from flatness by the same device?

That's what I was thinking when I decided to build my own device to carbonate aqueous liquids. My wife and I got both a whipped cream maker and a seltzer maker (both by iSi) as wedding presents, but the instructions say clearly not to get experimental with either; just cream, just water, respectively.

The principle was simple, and this was a year or so before the prices on SodaStream devices came down to under $100.  I would mount a standard Schrader valve--the same thing you use to fill a bicycle or car tire--to the cap of a soda bottle. Then I would attach the chuck you use to fill such tires to a CO₂ tank from my paintball gun, and use that to charge whatever liquid I put into a soda bottle with fizzy goodness.

I spent more than the $67 this starter kit costs, though I also had more fun.

I rode my motorcycle out to a paintball shop in Baltimore County to get my old paintball CO₂ tank filled. The owner thought the idea was great, and he was in the process of retrofitting his existing equipment to refill SodaStream CO₂ tanks, so he was sympathetic to my goal. But my tank was out spec, so I had to buy a new one for $30 bucks. With some advice from him, the parts to connect up the Shrader chuck cost me another $25.

If I were fancy, I'd attach a regulator. But the hope was to do this on the cheap, and even the most basic inert gas regulators cost around $50, plus the extra plumbing to connect it would have been another $15 at least. Truth is, the needle valve that comes with the paintball fitting for the tank seems to deliver CO₂ at soda-bottle pressures just fine as long as you're careful.

The next part was to mount Shrader valves into bottle caps. I drank more soda in a week getting bottle caps to work on than I normally do in a month. $7. After a few tries, I was able to get a decent hole drilled by starting it with a very small normal bit and then widening it with a stepper drill bit. The trick was to do it without shredding the rubber seal on the underside of the cap. Then it was just a question of putting the valve through the hole, tightening everything down, and putting the bottles under pressure.

The stepper drill bit is honestly one of my favorite tools, as a side note. 

Problem is, it doesn't work. And what kills me is that I'm not sure why. I got the liquids cold. I tried plain water, sweetened stuff, flat soda. I tried shaking it and not shaking it. I tried 2-liter bottles and 16-oz bottles. I went dutifully for days adding more CO₂. The best I got was with lemonade, and even that was a very weak fizz, not half of what you'd get from a new bottle of soda. It did also make some milk truly, deeply, repulsive.

I'd love to tell you that this DIY system worked, and SodaStream can go take a hike. If you have any suggestions on what could be done to make this system work, please share them in the comments. But when you consider that the commercial devices cost less than what I spent by at least a 25% and they, y'know, work, this whole thing was an entertaining boondoggle.

Close up of a really cool idea that doesn't work and I don't know why.