The Problem: Seltzer water from the store is delicious but expensive. My wife drinks about 5-7 bottles a week, and at a dollar a bottle, this adds up.
The Solution: Creating your own soda water, also known as. sparkling water or seltzer water, is as easy as combining pressurized carbon-dioxide and cold water. We just need a few pieces of equipment, and acompressed CO2 cylinder. Here's the setup I whipped up in about 5 minutes for my New Year's Eve Party featuring Artisinal Litchfield NH Soda Water, based on this article.
Adjustable Pressure Gauge - $51.45
Gas Line with Ball Lock - $10.58
Threaded Cap - $19.99
CO2 (beverage gas) from your local supplier - ~$100 for the cylinder, then $15 per fill-up. One fill-up per year
This gauge measures the pressure in the CO2 tank, and has an adjustable knob for how much pressure you want to apply to your cold water to carbonate it. A good amount of carbonation is about 30PSI for that nice tangy zip you're familiar with.
This connects to the pressure gauge and routes the CO2. No gas will flow with just this attached, you need to plug in the threaded cap to get gas to flow
Plug the threaded cap into the end of the Gas Line. Then screw your soda bottle filled with cold water into the threaded cap. Energize the CO2 and shake vigourously for 30 seconds. Boom, you've got soda water! Flavor as desired.
Any local welding supply store or restaurant supply store is likely to be able to supply you with reasonably priced CO2 cylinders and re-fills. Typical sizes are 2.5 pounds or 5 pounds. Anything larger is huge and probably overkill. The trick is to ask for "beverage gas". Tell them that you're looking to make a soda machine, or to brew beer. Here's the local place that I used to get my CO2 tank, a place called Maine Oxy, a welding supply store. Here's how they advertise for CO2