DIY CO2 w/brass hose barb connector - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 08-05-2013, 02:19 AM Thread Starter
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DIY CO2 w/brass hose barb connector

I was going to go with a pressurized CO2 system for my new 75g dirted/planted tank but decided to first increase my measly stock lighting by adding a double T-5 along with my stock lighting. Well that blew my budget for now so I started building my own DIY CO2 generator. Pic below is after the lighting upgrade, I still have a good bit of tannins in the water from the Mopani wood, it took about 6 months of weekly water changes to finally get the water clear up in my other 29g tank.
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DIY CO2 in progress:
Supplies:

1] 25ft polyethylene 1/4" tubing (supposed to be CO2 proof, it's a little more ridged than vinyl but still flexible enough to use. This size fits very tightly on the brass barb. Tubing $3.00 for the roll

2] Brass barb, 1/4": $3.00

3] 2L soda bottle, free I guess as I drank the contents.

4] Plumbers "Goop": about $5 for a tube large enough to last me the next 10 years (if only it would keep that long).



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I decided to get a 1/4 brass barb, heat it up and carefully push it through the 2L cap thinking this would make the tightest possible connection.
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It took me 2 tries to get it hot enough to melt through the cap. I kept the soft inner plastic washer in the cap because I know that is what helps keep the seal on the soda bottle, I just melted through both of them.
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I then pulled the barb back out, cooled it under water then dried it off very well.

I put a decent amount of plumbing "goop" on the inside of the cap, but not too much as I didn't want it to interfere with the threads. This created a really good seal on the inside between the cap and the brass barb. Then I carefully put some around the MIP end of the barb on the outside of the cap in a " ring" around it to make a top seal. I think the seal is pretty good because a very small amount was pushed through to the outside of the cap when I put the barb through the hole I melted.

So here's the final product:
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I'm going to let this cure for at least 3 days to let the VOCs evap off. Regarding the use of plumber "Goop" I found a number of people online who had used this "because it is one of the few glues that will adhere to poly-E and poly-U which the cap is probably made of. I found no instance reported of any residual VOCs causing harm to any of their fish or plants.
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post #2 of 9 (permalink) Old 08-05-2013, 02:30 AM Thread Starter
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My idea of a setup for the CO2 system that utilizes my air pump.

Here's the general idea...

DIY CO2>short tube run with bubble counter inline>check valve>brass T

On one side of the brass T I'm thinking about connecting my small air pump.

Air pump> short tubing with check valve> brass T (from above)> tubing>fine airstone inside tank.

Im thinking I might get the best of both worlds here. The air will mix with the CO2 and both will be diffused into the tank by the airstone. So this way I'm getting O2 as well as CO2 into the water. The airstone will diffuse the CO2 better than just having "standard" size bubbles of CO2 being put into the tank. Everything I've read seems to tell me that just putting a DIY CO2 generator will not have enough pressure to create fine bubbles from an airstone, hence why I'm thinking of utilizing my air pump to help me do this. Anyway, Im going to give it a shot and see how it works. I'm going to put the airstone in the bottom of my tank under my Hydor wave maker which should provide even more diffusion for both the O2 and CO2. And the check valve from the CO2 line will prevent regular air from getting into the CO2 generator, the natural pressure from the CO2 generator will allow CO2 to be mixed into the air at the brass T.
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post #3 of 9 (permalink) Old 08-06-2013, 03:09 AM
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Looking forward to what you come up with.

I tried 3 different strategies for a DIY CO2 system, and used a powerhead with the airline fed through the propeller cage, which diffused the large bubbles into tiny bubbles. I then switched over to an airstone for a diffuser. The main reason why I switched, and eventually threw out the CO2 system was because I couldn't come up with a cheap enough method to keep the CO2 in the water.

The airstone produces too much water agitation, as does the powerhead I had the airline fed into. I read that with a lot of water agitation, the CO2 has less time to dissipate in the water column.

I had this CO2 system going for nearly 2 months with no results :-/

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post #4 of 9 (permalink) Old 08-09-2013, 06:27 AM
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I'd be interested in how long this configuration works before it starts leaking. I tried with plastic air line couplers and/or check valves a long time ago. I tried putting either/both below the cap and above the cap. The result was always the same -- leaks. Sealants didn't help.

What finally worked for me? Fitting on the outside. Nut on the inside. The plastic cap and liner became a very effective sealing washer when compressed between the fitting and a washer and nut.
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post #5 of 9 (permalink) Old 08-09-2013, 06:44 AM
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@MrG: Probably dating myself here, but what worked for me was to maximize contact time with water. Running the CO2 into the canister caused cavitation. Running the co2 into the canister output resulted in 80% (estimated) waste. I ran the CO2 down the uplift tube and turned the entire underside of the UG filter into a reaction chamber. Very effective. Had _very_ good results.
Today, I run dirt substrate with no UG...and no CO2. Not sure how I'd do it today. Bubble ladder? Large capacity (large surface area?) reaction chamber external to the tank? Dunno.
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post #6 of 9 (permalink) Old 08-09-2013, 06:52 AM
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Here's my set up when I used DIY CO2: I drilled a small hole (smaller than the outside diameter of the CO2 tubing) through a 2L soda bottle cap, cut a short length of tubing ~6", cut an angle at one end and pulled that end through the hole a couple of inches (cut end inside the cap). Gooped both sides of the cap with silicone. I made two bottles like this. I put a check valve at the end of each tubing sticking out of the caps, then with a t-connector, connected the two bottles together. I did this so I could stagger changing the bottles weekly without losing any pressure in the remaining bottle. I just unscrewed the bottles to switch out the bottle (I always started a new bottle a couple of days before changing a bottle), leaving the tubing intact. I diffused the CO2 into the tank using an internal filter (a Duetto). I had a drop checker in the tank (a standard 10 gallon) and it was always green and plants thrived. This system never leaked in the two years it was in use.
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post #7 of 9 (permalink) Old 08-10-2013, 06:52 AM
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@mayanjungledog: So drill a hole small enough to create good friction, but not so small to cause the tube to buckle. At low pressure, I can see this working without leaking (measurably) with or without "goop". In retrospect, part of what caused the leakage on my set up was trying to remove the bottle without disturbing the cap (spin the bottle without moving the cap). Ultimately for me (bull in a china shop), a good compression fit was best.
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post #8 of 9 (permalink) Old 08-10-2013, 06:19 PM
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I did something similar if anyone is interested: https://www.plantedtank.net/forums/sh...ad.php?t=77476

Same idea but a few more parts.

-Matt

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post #9 of 9 (permalink) Old 08-11-2013, 10:19 PM
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@djjcoleman: yes. Probably would have been just fine without the addition of silicone too. I did a similar process to inject CO2 (not DIY) directly into the outflow tubing from my eheim filter into an external reactor. No silicone on this set up.
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