I drink a lot of seltzer water. But I got tired of buying my seltzer at the store and paying anywhere from 50 cents to a dollar per liter. I also drink a lot of soda pop, which is even more expensive. So I looked at various options. I bought a bar gun and carbonator from a defunct restaurant, but I managed to burn up the carbonator while failing to make it work.
I was keeping an eye out for an old fashioned soda syphon. Then SodaStream came out. I looked at it, but two drawbacks became apparent. The proprietary sodastream CO2 canisters, and the soda stream flavors all used various artificial sweeteners, which I think all taste nasty.
So, I was researching various other options, and I realized that since I was not a high volume (like a restaurant) user, I could carbonate my water overnight. So I started looking at using a Corneilius keg as a carbonator. I bought one, got the CO2 tank and regulator, hooked it all up, and it all worked. I'm not going to share the dead ends I went down, but there are some significant cautions.
This device is creating a food for human consumption, so you do have to clean and sanitize everything that is going to come into contact with the water. Insides of the tanks, tubing and so on. Also, significant health risk with carbonated water that you only use stainless steel or plastic fittings, tubing and so on. Carbonated water is a weak acid, and if left in contact with copper or brass fittings, it will leach the copper into the water, which will poison you.
You are also are using pressure vessels. If you overpressure them, they can explode, flinging sharp shards of metal out to cut you open and destroy your body. The Corny kegs come with pressure relief valves to keep them from exploding, don't mess with them. Bleeding to death from a seltzer machine accident will just give you an entry in the Darwin awards, and we don't want that. Poisoning yourself and your family with copper is also pretty sad, so don't do that either.
The CO2 tank is also dangerous. Dropping it and breaking off the valve will turn it into a rocket. Mythbusters showed us that it has enough energy to smash through a brick wall. You don't want to see what it will do to any part of your body it smashes along the way.
So, now a bit of the physics of carbonation. The main thing is that the temperature of the water and the pressure of the CO2 are important. The colder the water, and the higher the CO2 pressure, the more CO2 will dissolve in the water. So if you are keeping the water tank in a non-temperature controlled enviroment, like I am, you will find you have to mess with the CO2 pressure to compensate. Also, if the water is warm enough, it will all fizz out in the time it takes to pour from the spigot and reach the bottom of the glass, so keeping it outside on a hot summer day will not work. For selzers, we generally want a high carbonation, so I keep the pressures in the neighborhood of 30 psi, but this is a matter of personal preference.
I'm not going to mention specific suppliers here. If you have a homebrew beer supply store near you, they will have or can order everything needed. But you have to be careful with what they order. Some of the beer dispensing valves are chrome plated brass, and carbonated water will leach the copper out and poison you. This is not an issue with beer, so the beer store folks may not realize this matters. CO2 tanks and regulators can also be easily obtained from local welding supply stores. You can find all of this stuff online, for less money, but since the stuff is heavy, shipping costs will often make that not such a good deal.
So onto the hardware. First we need a tank of CO2 and a regulator to give you CO2 gas at desired pressure. You typically will need to buy these, then refills from your local supplier will be less expensive. This is the 20 pound size tank, which is pretty common at the welding shop. I have been using this tank for ten months, and it is getting low, but still is fine. As long as you don't have any leaks, you don't use very much gas. I also keep the tank tied to something solid, like the table leg. I pulled it out for this photo. Also, the 20 pound is how many pounds of CO2 when full. the tank is something like 50-60 pounds when full, and awkward to handle, and it will mash your fingers and toes if you are not careful. Tank was about 50 bucks, and the regulator another 50.
Also, your tank will come with one gasket, don't lose it. It goes between the regulator and tank to seal. Some regulators have a permanent gasket built in, so make sure you do the right thing. The way you adjust the pressure output from the regulator is the little screw on the bell. It's backwards from what you expect. The two gauges show the tank pressure and the output pressure respectively. Tank pressure is thousands of PSI, output pressure is tens of PSI.
Now the Cornelius keg or corny keg or korny keg. These are available as small as 2.5 gallon and up to 20 gallon size. This is a five gallon size, which is the most commonly available. The soda industry used to use these in vast numbers for soda fountain service, and they are still readily available used. Anywhere from 45-100 bucks each, used to new. There is a gas in and a liquid out fitting, and these are different. So if you are forcing it, you probably are trying to put it on the wrong one. the detachable fittings can be pin lock(coca-cola) or Ball lock (pepsi and everyone else) Pick one version and stay with it.
The gas in port has a short piece of pipe inside, about an inch long. The liquid out port has a long dip tube that goes right down to the bottom of the tank so it will siphon up all the product inside. I have modified this one as a carbonating tank, by replacing the short tube with a long tube so that the CO2 gas will bubble up into the water, speeding up the carbonation process from a couple of days to overnight. I could add a carbonation stone to the end of the tube, which makes the bubbles smaller, which will further speed up carbonation, but I find I don't need that. When ordering parts for kegs, there are several manufacturers, be careful you get the right parts for your keg.
The large oval port is removable, and that is where you fill it with water. The pressure relief valve is in the lid as well. Again, don't mess with it. Five gallons of water is about as heavy as I care to lift, so I'm not interested in a larger tank, and larger tanks are expensive. More cost effective to buy another keg and add it in as a reserve tank. The gasket on the lid will need to be periodically lubricated with food grade grease. Brewers supply place with have that, and sanitizing solutions to kill off the bugs. You will also have to wiggle the cover a bit when pressurizing as it sometimes will not seat correctly, spraying water into your face. You have to disconnect the in and out fittings, and bleed out the internal pressure before you can open the fill port.
JUmper hoses can be as long or as short as you care to make them. They have a gas fitting on one end, and a liquid fitting on the other. When in doubt, order them with longer hoses than you think you need. Or just buy the fittings and a roll of pressure tubing to make then custom length. Buy proper food grade beverage tubing that is rated for 100 PSI usage. OF the correct size to match the fittings.
Dispensing. All you need is what is called a picnic faucet. these are about 20 bucks and the homebrew store should have them on the shelf premade. Use only the plastic ones or ones specifically made for soda pop. Connect this to the liquid out port and enjoy.
Now, as you can see in the pictures, I have more than just a single keg. This is for a couple of reasons. I initially got the 2.5 gallon keg, and found it was inconveniently small, and when it ran out, it took a couple days for the water to fully carbonate. So, I bought the five gallon keg (well, actually two, as the place was running a two-pack special) Just put a jumper connection and I know the main tank is empty when I cannot hear the water gurgling into small tank after I finish pouring. Leaving a reserve supply of seltzer while I go refill the carbonator tank.
As a happy coincidence, I can also bring the whole setup to a picnic and put the small tank floating in a cooler full of ice water. By looking at the cooler, once the main tank empties, the small tank starts floating higher in the water, so I can tell at a glance that the main tank needs refilling. I can speed up the carbonating in the main tank by gently shaking it to cause the CO2 to absorb faster. Takes about ten minutes instead of overnight. The smaller tank in the ice water will also ensure the seltzer is ice cold. As less carbonated water flows into the small tank, it will actually reabsorb the gas and the tank will sink back down by itself.
I also can bring just the small tank full of carbonated water with me on short trips, and using the tiny CO2 cartridge pressurizer to maintain pressure, dispense the full tank for smaller parties or just for myself. Way way less expensive that hotel vending machine soda pop. That is also available in the homebrew store. Don't try and carbonate with that though, you will need lots of cartridges. Expensive and a hassle.
Finishing touches. I like drinking seltzer with a shot of lime juice. Just enough flavor to be there, but no calories. I also have various syrups that I can make soda with. Look for Italian soda syrups. Monin and Torani are the two brands I like. Peach and apricot are my favorites. Put in one part syrup in your glass, five parts seltzer, stirring with a spoon as you are filling the seltzer in, otherwise the syrup stays down at the bottom of the glass. Add ice last.
Next step is putting the whole setup in a fridge. I'm thinking one of those chest freezers, hacking the thermostat to keep it at just above freezing, big enough that I can put the whole setup inside without having to drill any holes in the thing. Normal style fridges are not really big enough to put everything inside, and I don't want to drill holes in them, possibly letting the coolant out or breaking them otherwise.
Down the road I'm contemplating adding the bar gun and soda syrup pumps to this setup, also a still water system using compressed air for fruit juice from concentrate. I am a big fan of cranberry juice which would work well for this.
Hope this is useful.
Step 5: A Year Later....
Edit, a year or so later.
So, all those future plans got put on hold due to long term illness in the family that ate my free time. The system is still pretty much exactly the same as described. But I'm starting to get leakage at the connections where I plug in the hoses to the tanks. Over time, the connection had slightly unscrewed on one tank, allowing water and CO2 to seep out. This was fixed with just applying a wrench and tightening it back up. But I'm still seeing a tiny bit of seepage on the connections to the larger tank, which are the ones I put the most disconnect-connect cycles on. Every time I refill the tank. So I need to order a couple sets of gaskets, and relocate the tube of food grade grease. In the meantime, just putting a drip tray underneath the tank is taking care of the problem. the seepage is slow enough that it evaporates before I need to empty the tray. Mostly doing that to keep the water from damaging the wooden floor it is sitting on. It has also dramatically increased my CO2 consumption, bleeding out an entire tank in a couple of weeks until I tightened it. So this year my CO2 cost doubled to about eighty dollars. But at a 99 cents per liter from the store, I'm still well ahead.
I have bought the cranberry juice syrup and cola syrup, but about the time they arrived my dad got sick and they have been sitting on the shelf ever since, along with all the other free time projects I have. My consumption has been about one tank (600 ounces) each couple of weeks in hot weather, about one tank a month in colder weather. With spikes whenever we have a big family event here. Things are getting better on the home front, and I hope to get going on the next step, which is the fridge. Keeping an eye out on craigslist for a used chest freezer of the right size, but I only see the too-small ones and the too-big ones. That suggests that is the sweet spot for chest freezers, so I probably will have to bite the bullet and buy a new one.
Edit again, about two years later. The machine was in my home chugging away providing all my seltzer needs, when we had a fire. Everyone got out safely, which is the most important thing. But the machine is now coated in this incredibly difficult to remove coating of black gunk that is the smoke particles settling onto the thing. More than likely horribly toxic. It still is holding pressure and dispenses seltzer, but will probably be tossed and the insurance company will give me not enough dollars to replace it. If I do choose to save it. I expect I will throw away all the plastic bits and the tubing. The canisters are stainless steel, so should be cleanable. *sighs*