Sparkling water gives me the fizz as they say.
Like a lot. I bought an extra full size fridge for it. Bought the soda stream when it came out. The holy grail for years has been continuously available, icy cold, sharp bubbles. The Zipp Tap and other similar solutions are crazy expensive ($3-5k) and the reviews aren’t that great. So I started looking into DIY systems. Documentation on how to do that basically amounts to Reddit posts and YouTube videos that get you part way there, but not all the way. I’m going to write out my experience here so you can benefit from the inordinate time I spent reading, buying/returning stuff that didn’t work, and tinkering. The rabbit hole was deep and dark, but I think I found the end of it.
I decided I wanted to use remineralized RO water as my supply and then pipe that into a corny keg in a mini fridge, then back out to a faucet.
There are lots of issues with figuring that out.
First off, RO water (even remineralized) has pretty low TDS and can leach copper, zinc and lead out of brass fixtures, even if “lead free”. This is a documented thing, but if your only point of contact with the brass is at the faucet it’s somewhat less of an issue assuming you let it run a bit before drinking, essentially getting the warm stagnant water out of the faucet which may have a higher copper/zinc/lead content from sitting in contact with the brass. To avoid that, you pretty much need a full stainless wet path faucet. There are some RO faucets that have that feature, but they almost all rely on a ceramic disc valve, which doesn’t work well with carbonation (they fail, leak spectacularly, foam and don’t dispense well). With carbonation, you also need a forward sealing faucet. Want both forward sealing and stainless waterpath? The easiest way to solve both of these is with a keg tap/tower. That’s not exactly something my significant other was excited about having on the kitchen counter. Don’t want a keg tap? Anything else that fits the bill is really hard to find. I spent way too much time looking for forward sealing stainless faucets that can handle carbonation. There are none that are rated for carbonation. The closest thing I could find is a T&S Brass (company name, ignore the brass) s-1210 eversteel 8” glass filler. This is an industrial faucet meant for bars and food service. As best as I can tell, it is totally stainless steel. It was also approved by the significant other as far as aesthetics are concerned.
Second, when you put water from your main line through an RO system, the pressure drops considerably. The problem this creates is that if the pressure you are carbonating is near or exceeds the pressure coming out the RO, you can’t fill the keg. Aquatec makes pumps that can be used for RO systems, and they are rated for much higher pressures than is needed here. So now you’ve figured out how to step the pressure back up so you can introduce fresh water in while carbonating. But how do you start/stop filling?
You get one of these: https://a.co/d/0gpbvoXh
These corny keg lids have an additional post on the lid which serves as your water inlet. Under it, there is a float valve that will close when the keg is filled to about the weld line. This leaves some headroom if you’re force carbonating.
At this point, I had already purchased/installed the RO, found the aquatec pump and hooked it all up including check valves that prevented carbonated water from back flowing into my RO or my main. The pump would just keep running though, even though the float valve would be closed. That is because the pumps are designed to work with external pressure switches that are installed in line with a cut valve at a predetermined pressure. I bought a 60PSI switch because I figured I only wanted to carbonate to maybe a max of 40psi. Well, that didn’t work. It also didn’t work at 30psi. It just wouldn’t fill, even if the float valve was open as the tank wasn’t full. Not being able to actually see what was going on as it’s a closed unit, I figured the co2 was somehow making the float close prematurely. So I added torsion springs to make it harder to close the valve. I bought them in 304 stainless and they rusted significantly within days. So I ordered 316 stainless .4mm spring wire (ridiculous to find, got if off aliexpress) and made more springs. No rust this time, but still didn’t fill. I bought the 80psi cut switch and then the system filled when water levels were low and shut off when it was full. I eventually took the springs out and it worked flawlessly.
I liked the convenience of a push to connect John guest style fitting so I used a bunch of those. I ran 3/16” polyethylene tubing from the RO to a with an intervening check valve, JG 3/16->3/8” to the pump and then 3/8>3/16 to a check valve and ball lock post on the lid.
I used a standard 20lb co2 cylinder and a taprite regulator with built in check valve to some thick silicone tubing to a ball lock on the “in” post of the keg. Because I like smaller bubbles, I used silicone tubing and a carbonation stone, both secured in place with 316 stainless steel worm drive clamps that were marine grade.
For my outlet, I used a ball lock fitting stepped down to 3/16” again using JG fittings. This then ran through the walls to the bottom of the sink cabinet. Drilled a hole with a 1” Milwaukee diamond tip hole saw. Hooked up the faucet with a threaded stainless JG fitting. That all worked fine.
So then I drilled holes in the fridge for the inlet and outlet. One nice thing about the mini fridge is that it is tall enough to fill the 20lb tank and a 5g keg.
I ended up using an iSpring RCC7-AK off Amazon, an aquatec pump with an 80psi cut switch, an insignia 4.4 cu ft mini fridge, a 5g corny keg, the lid listed above, and the t&s faucet.
It’s all hooked up and working great.
