DIY Carbonator for Making Sparkling (Seltzer) Water at Home

This article discusses how to make your own DIY setup for carbonating liquids. This project been documented nicely by others on the web, including Popular Science. Read on, though, for more details on a thifty, yet high-quality system.

Parts List

Below I have listed the prices I paid in October 2015, and the sellers from whom I purchased the parts. Because many of these parts are heavy or specialty items, prices vary significantly between sellers and across time. I found a seller who had a fixed shipping cost, but otherwise low prices; I bought most of the parts from that seller and saved some money.

For example, try to find a seller that doesn't offer Prime shipping, but only charges a flat rate for multiple items. Amazon doesn't make this process easy; you may have to put various combinations of parts from different sellers in your cart and note the final checkout price with shipping.

PartPriceSeller
5 lb. Aluminum CO2 Tank $53 HomeBrewStuff
Taprite Dual-Gauge CO2 Regulator $50 Beverage Elements
5/16" Gas Line Assembly, Ball Lock $7 HomeBrewStuff
CarbaCap Plastic Carbonation Cap $11 HomeBrewStuff
Total:$121

Obtaining CO2

In my area, the only local supplier of carbon dioxide is Praxair. Drop off your empty tank, and they'll give you a full tank for about $20. They manage their tank inventory, testing the tanks for safety and retiring tanks as necessary. When you swap a tank with them, this is a benefit you receive, and it's included in the fill price you pay.

If you buy a full tank from them without trading in, they charge around $125. So buy an empty tank and trade it in.

Assembly

This is straightforward. You only need a screwdriver to secure the metal tube clamps and a wrench to lightly tighten the regulator onto the tank.

Use

I carbonate my water at about 3 bars (45 PSI). Using cold liquid facilitates carbonation. I leave some air in the bottle and push it out when screwing on the carbonator cap. This lets more CO2 into the bottle. I shake the bottle to diffuse the CO2 into the liquid for about 30 seconds. I let the bottles sit for a few minutes to settle before removing the carbonator cap and replacing it with the standard cap.

I buy two plastic 1.5L bottles of sparkling water from Trader Joe's every three to six months. I reuse these bottles repeatedly, until I recycle them and buy a new pair of bottles.

Every time I refill my bottles, I make a mark on the bottle. My idea is to retire the bottles before they pose a risk of exploding. I'm not sure when that would happen, nor has it happened to me in almost a year of practice. But I figure that retiring bottles after 30 refills is reasonable.

Other Considerations

Dual Pressures

Of course, you can use a CO2 tank to carbonate a keg of beverage (beer, seltzer water, kombucha, soda). You can also use a CO2 tank to serve a keg of beverage. Carbonation is done at a higher pressure. Serving is done at a lower pressure—roughly the pressure at which the beverage flows from the tap.

You may want to be able to carbonate and serve simultaneously. For example, if you want to be able to carbonate water while you have a keg on tap, you need a dual-pressure regulator! So before you buy a regulator, think if you might find two pressures useful in the future. The Taprite Dual-Pressure CO2 Regulator costs about $100.

Once you have two pressures available, you can connect many lines to each pressure using an "air distributor" or "CO2 manifold" (e.g., this two-way manifold. So you can easily have one line to carbonate and have many kegs on tap at serving pressure, as long as you have a regulator providing two pressures. A small CO2 tank will have trouble keeping a large manifold at a steady pressure; if you want many taps, consider a larger tank or a regulator with more outputs (splitting each into fewer lines with smaller manifolds).

Metal Carbonator Cap

Metal carbonator caps seem to be available now. I'd probably buy this one:

PartPriceSeller
Stainless Carbonator Cap $9 HomeBrewStuff
Value (Benefit-Cost Ratio)

I find Taprite's quality to be high, but a little more expensive than Kegco or generic alternatives. My impression is that some brands of regulators and tap hardware (e.g., Taprite) are much higher quality, but only a little more expensive; you get what you pay for.

Hope this was helpful!