inconsistent/inadequate pressure in new CO2 system

[HarlanH]

Hi, I'm trying to set up a CO2 system for a 20-gallon well-established planted tank. Here's the stack:

* SodaStream
* SodaStream adapter
* single-gauge CO2 regulator (got this one because the SodaStream adapter doesn't work with American-threaded systems, and the voltage issue precludes using most European regulators)
* solenoid valve on the same timer as my lighting
* plastic check valve
* combined bubble counter and ceramic diffuser

It almost works. The solenoid works, the diffuser works nicely, etc. But I'm having a hell of a time getting the regulator set to a level that's appropriate for my sized tank. I set it to a reasonable flow, which is tedious but possible, but in the morning, the water's siphoned up to my checkvalve, and the pressure seems inadquate to clear the line.

What's going on? Would a very slow leak somewhere cause this? Or am I using inappropriate equipment in some way?

Thanks!

 

[HarlanH]

Any thoughts on this? One other idea I had is that my tubing might not be appropriate? I'm using a flexible blue airhose tubing. Might it be too flexible, and ballooning in a bad way?

 

[dcutl002]

CO2 tubing is different from air tubing. Air tubing will corrode from CO2.

 

[FishCr8zy]

Do not, I repeat do not use airline tubing for pressurized co2. Air tubing is more porous than co2 tubing and will release almost 50% of the co2 traveling through it. That is most likely why you are not having enough pressure. You could also have a leak somewhere which is why I just siliconed all the places where the tubing met with something. Both are valid reasons and even more likely is both are the reasons you are having leaks.

 

[dcutl002]

What he said.

 

[HarlanH]

FishCr8zy, thanks for the clear answer! I hadn't understood this previously. Will pick up some better tubing and report back soon!

 

[FishCr8zy]

No prob

 

[Jkeating8]

Do not, I repeat do not use airline tubing for pressurized co2. Air tubing is more porous than co2 tubing and will release almost 50% of the co2 traveling through it. That is most likely why you are not having enough pressure. You could also have a leak somewhere which is why I just siliconed all the places where the tubing met with something. Both are valid reasons and even more likely is both are the reasons you are having leaks.

Just curious, but how do you know it releases 50% of co2 traveling through the line? I've always used airline tubing and I get 3 months on a paintball tank. I use an obscene amount of co2. I think that is a bit of an exaggerated statement.

 

[FishCr8zy]

It's an estimate. People say 25%, 75%, etc. I made an estimate that is 50%. Some lose less, some more.

 

[HarlanH]

OK, I've upgraded to CO2 tubing, and that does seem to help somewhat, but I'm still having problems. I don't think I have a leak -- I've tried the soapy water trick, and all the joints seem fine.

I can regulate the flow rate during the day to something appropriate, and my plants are happily making O2 bubbles. But the next morning, the lights turn on, but the CO2 is not moving.

In order to get it to work, I have to fairly drastically open up the regulator (increasing the pressure) until the gas starts going through the diffuser. At that point, the flow rate increases a lot, suggesting to me that there's a nonlinear amount of back-pressure. It's like classical friction. If gas is flowing through the diffuser, then the back-pressure is low, but from a standing start, you need more gas pressure to get it going.

But I can't possibly set the regulator permanently to a high enough pressure to get it past this initial friction, or I'll have aquarium soda and dead fish.

What's the trick? Should I use a different type of diffuser? I'm using one of the combo bubble-counter and ceramic diffusers. Maybe one of the plastic maze diffusers that won't have back-pressure? (But will be much more wasteful?) I've also thought of switching to a fancier timer and maybe just running the CO2 for a few minutes each hour at a higher pressure, but I'm not sure that's a good idea.

Thanks!