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· Registered
166 Posts
This is the set of directions I followed.

My first attempt failed likely because the lukewarm water I used to mix the yeast was probably too hot. Another possibility for that failure was not using baking soda.

If you sterilize properly, your CO2 generator will be running in a few hours.

This is what I do:
a) Rinse bottles and caps in hot water. Then submerge in cold water. Either the hot temperature or the sudden crash will likely kill most bacteria.
b) In a separate container mix well the 2 cups of cane sugar with 2 cups (a bit more is OK) Reverse Osmosis processed drinking water.
c) Stir that mixture into the 2L bottle.
d) Mix some hot water with cold water to obtain lukewarm or tepid water (e.g. within the 30 to 40C = 86 to 104F range), add the yeast, mix well; add the baking soda, mix well.
e) Stir this yeast-baking soda lukewarm water mixture inside your 2L bottle. Refill if needed until the upper curvature if using Coca-Cola bottles.
f) Clean carefully your bottle to avoid bacterial build up and remove the not so good smell.
g) assembly as needed. Shake vigorously and wait.
h) Check for leaks and fix as required.

I use the 20oz. bottle gas separator, actually running two 2L in a 29g bow and 3 2L in a 45g long. My DIY drop checkers confirm safe and steady CO2 levels (light green). My plants love it!

I replace one 2L bottle every week no matter what; that way the output remains somewhat constant.

I will eventually go pressurized, in the meantime, it's kind of fun to do this. My 4 y.o. daughter helps me on this task.

Santo Domingo

· Registered
910 Posts
Also i read to set up a side reaction with the yeast and some sugar. So for example if your using 1/2 a table spoon of yeast mix that with 1/2 a table spoon of sugar and ~a cup of warm water (~96-104*F. This should feel slightly warm to the touch, not hot but just warmer then your body tempature).

Mix well, make sure well mixed and airate. Let it sit and keep mixing every ~5 mins to keep mixed, once you see bubles or some foam starting on the top the yeast is proofing. From there add it to your mixture. I've read that mixing it with everything intially can kill the yeast.

· Registered
310 Posts
most diy co2 problems are leaks. they leak easily and sometimes you think its good and its not. ive been using this recipe for months with success.

2 cups sugar
1/4-1/2 tsp yeast
3-4cups water.
i use fairly hot water and shake well. bubbles in few hours.

make sure your hoses arent leaking at the spot on cap and check valve.

i dont use ro water or steralize the bottle lol. never heard that before now.

what are you using as a diffuser?

· Registered
345 Posts
most diy co2 problems are leaks.
If you have followed the directions in that link to the letter, I can almost guarentee you have leaks occuring where those screw in barbs are located. Possibly also at the check-valve joints. I learnt very quickly that the more joins you have in the system, the more likely you are to have leaks.

Using the "slightly smaller than the inside diameter of your hose" method, drill holes in the lid of your gas separator and soda bottles. Jam the hose in place, pulling thru with needle nose pliers. Delete all other unnecessary fittings (you can use a T-piece to connect the two bottles if you like). Others will say otherwise, but IMHO, you do not need check valves. Even if a siphon is created in your tank, it will only drain enough to fill the bottles. Being sealed containers, THEY WILL NOT, CAN NOT, OVERFLOW.

Mix, quick and simple:
2L bottle.
2 cups sugar (white, brown, or brindle, makes no real difference)
2 cups cold water, 1 cup hot water, 1 cup cold water. In that order.
Shake, allow to settle.
1/2 tsp Yeast (some like Champagne or Brewers yeast, I just make sure I have fresh Bakers yeast. The choice is yours)
Takes me three minutes to make this mix. Bubbles within 2 hours.

Note, if you are alternating refilling your bottles each week, get hold of one or two of those little airline clamps and isolate the to-be-filled bottle from the rest of the system. This will ensure pressure remains in the system (and CO2 in the tank) until the new mix is up and going. I leave this clamp in place until the just-filled bottle is hard with pressure, before removing.
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