I love carbonated water, but am sick and tired of buying it in bottles. There are home water-carbonating appliances like SodaStream, but I prefer not to have another countertop appliance. Can I install a carbonation device under my counter and have it available on a tap on my sink, similar to how under-counter water filtration devices are often installed?
I also prefer to have a co2 that can be refilled or at least recycled.
You need 3 major factors for this:
1) a source of CO2. Many people use paintball tanks which can be refilled. They come in 12 and 20 oz tanks so they would easily fit under your counter. But I bought a 20 pound tank as that seemed like the sweet spot for tank cost vs gas cost for me.
2) a tank to hold the pressurized water. For example, a 3 Gallon Pepsi style Cornelius keg is 17" high by 8.5" wide.
3) a way to keep the water tank cold. This is the hard part and I don't know of any easy solutions. I bought a 7 CF freezer and hacked the thermostat. It doesn't fit under the counter but my wife is ok with it because she drinks a LOT of carbonated water.
-- In response to the question about refilling the water tank:
The cheapest Cornelius kegs are used and hold 5 gallons/19 liters. That would last most people at least a week. So I just refill the keg as it gets empty.
I thought about other methods to refill the keg, partially with the aim of reducing the CO2 wasted when the keg is opened for manual refilling.
One idea is to buy a 2nd keg and use an air compressor to force water from the 2nd keg to the 1st keg. You would stop before the 2nd keg is empty so that air doesn't get into the 1st keg. Then you add CO2 to the 1st keg to bring it up to the desired carbonation level.
How much could you save by doing this? Typically there is 2 to 4 volumes of CO2 in carbonated water. Let's assume we use 3. In other words, 20 liters of water would use 60 liters of gas. Also that we use 1 bar or 15 psi to push the water out. That's an additional liter of gas per liter of water. At one liter of water consumed per day, that's 365 liters per year of gas wasted by opening the keg to refill.
There are 229 liters of gas per pound and I paid about $1 per pound, thus the wasted 365 liters of gas costs $1.60. I don't think this is worth any effort to avoid at my price for gas. If gas costs you more, you'll have to analyze the tradeoffs for yourself.
Note that 20 pounds gives 4,580 liters of gas while 1 liter of water per day is 1,460 liters of gas per year. This means 20 pounds of gas will last over 3 years.
If you wanted something really automated, you could use a weight sensor to detect when the water tank was running low and turn on a valve to let more water into the keg. This assumes household water pressure is higher than keg pressure. For me, water pressure at the street is 100 PSI and my regulator takes it down to 60, much more than the 15 PSI that the keg uses. If this is not your situation, you'd need a water pump. The weight sensor also needs to signal when the keg has enough water and turn off the valve.
You'd also need a pressure sensor to detect when the keg pressure is too low and inject more CO2. I consider this too complicated for home use.
Another reason I do it this way is that my wife and I love the taste of San Pellegrino. I read an article describing how to make it at home.
http://blog.khymos.org/2012/01/04/mineral-waters-a-la-carte/
I was able to find a local brewery supply house that sold "Burton water salts". Mixed into the water at an appropriate ratio (I use 1 gram per liter), it tastes very good.
Since I have to mix the minerals into my water anyway, refilling the keg and pressurizing it as a batch process is no extra burden.
Here are some photos, I hope a link to facebook doesn't break any rules.
https://www.facebook.com/media/set/?set=a.10151813156323324.1073741838.770693323&type=1&l=eaa13eed3b
There are a few option for carbonation the one you asked about with having a tap can be used for carbonated water an example of this here.
There are also DIY options using a 20Lb co2 bottle that just has a hose coming out from under the sink which you can connect to your own bottles and carbonize then as you wish a couple of examples are home carbonation system and truetex walkthrough
I have a kind of hybrid approach. I really wanted continuous flow so I went on ebay and bought a McCann's carbonator for relatively cheap. I have that pump water and co2 (100psi) into a corny keg inlet. The corny keg is sitting in a chest freezer I converted to a fridge (keezer). I then have the output through 30 feet (to reduce the pressure through resistance) out a standard beer tap. the bonus is the freezer has enough room to have another keg for some draft beer.
Due to the corny keg filling on the top and drawing out from the bottom, I would have to use a lot of water in order to ever notice the temperature difference. It also allows me to have it on tap at all times.
The corny keg approach is alright. But it takes time to carbonate, and maintenance to adjust the pressure, then readjust for serving pressure, etc..
For an industrial-like on demand carbonation system, this is what you want. It's more work, but it's also hassle free: http://www.homebrewtalk.com/f95/dedicated-sping-water-soda-water-machine-build-390573/
Have a look on youtube: grohe blue grohe red
Blue is a nice tap version developped by the famous manufacturer Grohe.
