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I'm hoping my plan to carbonate my kitchen drinking faucet is as easy as it seems, but would like some confirmation I'm not missing something:

In short, I want to hook my main water line up to a consumption-grade CO2 tank, the same way I would hook up a Keg. I have a separate drinking faucet connected to my main water line, and I'd like to add a CO2 tank, connected to a regulator, connected to an air line, connected to a keg coupler. The Keg coupler would also connect to my main water line, and separately connect through to my faucet. For a diagram of what I mean, check out: www.kegworks.com/blog/how-draft-systems-work/ [No affiliation].

I'm not concerned with chilling or filtering at this point, but in theory would I be able to add in a water filter that feeds into my main water line into the keg coupler down the road? Or would that create problems with making the filter system 'under reverse pressure' from the CO2 tank?

I'm also trying to avoid needing to get a separate water tank to keep under my kitchen sink as that space is limited and I'd like to keep refill trips to a minimum. If my current plan doesn't work, having a tank of filtered water that I periodically have to refill and put under my sink might be the next best thing.

I guess what I need to worry about is whether my main water line is pressurized enough to prevent the CO2 tank from simply emptying out into my water supply?Alternatively, would the pressure from the main water line 'overpower' the CO2 tank such that I would get minimal carbonation in the end product?

Per the comments, if I would need to keep the CO2 tank < the pressure of the water line (let's assume 50-75 PSI), would that sufficiently carbonate the water? If not, would it be possible to add some sort of one-way valve from the main water line that feeds into some sort of water collection tank, that then connects to the carbonation system, so that it could 'withstand' higher pressure?

  • Residential water supplies are commonly 50-75 PSI. I'm guessing that your CO2 tank would be considerably higher. You'd have to keep the regulator below the water pressure level. Would that carbonate it adequately? – isherwood Jan 17 at 21:25
  • @isherwood Okay that makes sense, and whether it would carbonate adequately is the question of the day, I suppose. Further details edited into the question based on this. – Grade 'Eh' Bacon Jan 17 at 21:32
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    CO2 is used to with beer to create pressure for the beer to flow, however nitrogen is more frequently used in commercial grade systems. Soda fountains use a motor driven carbonator to desolve to mix the CO2 into the water. Study up on commercial soda fountains to learn more. – Tyson Jan 17 at 21:44
  • @tyson Ahh, I guess that explains why my 'solution' seemed so much simpler, because the motorized solution would force the the CO2 to pass through more surface area of the water, I think. – Grade 'Eh' Bacon Jan 17 at 21:49
  • Found one on Amazon – Tyson Jan 17 at 22:25
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I don't believe this is going to work very well with the set up you have described. Carbonation of water requires that the CO2 dissolve into the water. Assuming you get the pressure all worked out, the surface area between the gas and the water is going to be tiny. If it worked at all, it would dissolve into the water line itself. My guess is only a few ounces would be carbonated at most when you open the tap.

Another thing to consider is that the colder the water, the more CO2 it can dissolve. This is why a hot beer is more likely to foam out and create too much head than a cold beer. Here's a graph of that relationship:

enter image description heresource

I think you might be able to manage this with a tank, though. Basically it would be a keg but you would need to have a water supply as well as CO2 for the water to refill through. I'm not sure there's something off the shelf for this but reverse-osmosis systems have a tank so there might be a way to cobble together parts for to make it happen. I'm not exactly sure how you would make it automatically refill.

You'd want to have some sort of check valve on the water line to prevent it from flowing back into the water supply. The CO2 tank should have some sort of pressure control valve just like it would on a keg system.

This wikipedia page has some good info on this. If 70 PSI is the right number for the water line, you would probably need to release the pressure from the CO2 in order to refill the tank. The amount of carbonation could be tweaked by the pressure from the CO2 tank. The higher the pressure, the more CO2 will dissolve.

One other consideration is that it the pressure is much higher than typical water pressure, the faucet might not be designed for that and/or it could shoot out too fast.

  • I suppose I don't really need the tank to auto-fill. If the tank is reasonably large, even say 5 liters, it wouldn't be too troublesome to reach under the sink once or twice a week, and flip some valves to allow the tank to refill until it becomes usable again. For your chart there, do you know a way to convert solubility of gas in g/KG into a PSI metric? I'd like around 15 PSI in the final product I guess, and not sure if that means chilling the tank would be needed for the extra 'oomph'. – Grade 'Eh' Bacon Jan 17 at 21:48
  • @Grade'Eh'Bacon I'm not sure I understand the question. The g of gas per kg of water is telling you the saturation point of the CO2 in water. It's not the best graph because I doesn't say at what pressure. Higher the pressure, the more CO2 will dissolve. The pressure I think you are referring to is what the effervescing CO2 would produce under normal atmospheric pressure? I'm afraid that's beyond my skills. – JimmyJames Jan 17 at 22:00
  • Fair point, I was asking for what the local pressure / effervescence of the water would be immediately after pouring into atmospheric pressure. Your edit is helpful as well, thanks. – Grade 'Eh' Bacon Jan 17 at 22:07
  • One last thought is that if I do need a separate tank to hold the water in some intermediate stage, I would suffer more for not having it chilled - because if the water could come straight from the main water line, it would come in at least slightly cooler than room temperature. – Grade 'Eh' Bacon Jan 17 at 22:09
  • @Grade'Eh'Bacon I'm sure there's a way to calculate that but chemistry was never my thing really. The wikipedia page (added the link) has references that might help in figuring that out. If you can get it working, I think you could adjust to your liking, though. – JimmyJames Jan 17 at 22:10

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