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Hello! I have a 36 gallon bow-front planted tank that I've been developing for about the past year. I've got a Milwaukee regulator for CO2 supply, and while I'd been feeding that into a power head for diffusion, I recently built an in-line diffuser after getting a new canister filter.

The problem is this: I've had a difficult time controlling the CO2 bubble rate. I will get it adjusted, and then it will creep and then open wide. On two occasions it's run away while I've been away from home, on one occasion killing *all* of my fish, on another I managed to save about half of them.

I talked to Milwaukee, and they said that the problem is most likely backpressure on the regulator. The regulator is designed to be operated at near-neutral pressure, and said that to test, I should disconnect the CO line from the regulator, and then be able to blow (with my mouth) into the CO2 line (into the inline diffuser) easily, they said. I tried that out, and could not blow hard enough to *not* end up with Backpressure from in-line CO2 diffusera mouth full of water. Clearly there is a ridiculous amount of backpressure.

I raised the diffuser as high as I could behind the aquarium to reduce the column pressure, but that didn't make any noticeable difference: there's still a tremendous amount of pressure pushing back on the regulator. What's clearly happening is that the canister filter is pushing water hard down the line. I've got a one-way valve on the CO2 line to protect the regulator, but that won't decrease the backpressure.

Clearly people use in-line filters successfully, but I can't figure out how to reduce that pressure. The constriction of the spray bar pretty much guarantees that there will be overpressure on the CO2 inlet line. And yet this works for many people.

Can anyone give me any recommendations here? If there's a problem in the diffuser, I can rebuild that. Obtaining a new regulator is probably out of the question, though, on my budget. Can anyone offer any advice?

Thank you!
-Charlie
 

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Hello! I have a 36 gallon bow-front planted tank that I've been developing for about the past year. I've got a Milwaukee regulator for CO2 supply, and while I'd been feeding that into a power head for diffusion, I recently built an in-line diffuser after getting a new canister filter.

The problem is this: I've had a difficult time controlling the CO2 bubble rate. I will get it adjusted, and then it will creep and then open wide. On two occasions it's run away while I've been away from home, on one occasion killing *all* of my fish, on another I managed to save about half of them.

I talked to Milwaukee, and they said that the problem is most likely backpressure on the regulator. The regulator is designed to be operated at near-neutral pressure, and said that to test, I should disconnect the CO line from the regulator, and then be able to blow (with my mouth) into the CO2 line (into the inline diffuser) easily, they said. I tried that out, and could not blow hard enough to *not* end up with Backpressure from in-line CO2 diffusera mouth full of water. Clearly there is a ridiculous amount of backpressure.

I raised the diffuser as high as I could behind the aquarium to reduce the column pressure, but that didn't make any noticeable difference: there's still a tremendous amount of pressure pushing back on the regulator. What's clearly happening is that the canister filter is pushing water hard down the line. I've got a one-way valve on the CO2 line to protect the regulator, but that won't decrease the backpressure.

Clearly people use in-line filters successfully, but I can't figure out how to reduce that pressure. The constriction of the spray bar pretty much guarantees that there will be overpressure on the CO2 inlet line. And yet this works for many people.

Can anyone give me any recommendations here? If there's a problem in the diffuser, I can rebuild that. Obtaining a new regulator is probably out of the question, though, on my budget. Can anyone offer any advice?

Thank you!
-Charlie
Hi Charlie,

I was really trying to figure out what was causing your problem until I got to this sentence.
The constriction of the spray bar pretty much guarantees that there will be overpressure on the CO2 inlet line.
Clearly the problem is the spraybar not being able to handle the output of the filter. Choices include putting larger/more holes in the current spraybar, building a longer spraybar with more/larger holes, splitting the output of the filter with a "Y" so some still goes to the spraybar but excess pressure is reduced using an output nozzle. You may have to add a flow valve on the nozzle side or most of the output may head that direction leaving the spraybar at a trickle.

 

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I think you may be dealing with a bit of marketing doublespeak when speaking to Milwaukee! We don't want to tell you the real problem so we'll tell you another story to throw you off.

What does a regulator do if we can't use them to provide pressure at the level we want? If you want to use 20 or 50 PSI, the back pressure should have no way of working for a time and then changing.
What can happen is that a poor quality needle valve can "float" or change position. It is a pretty common complain on the cheaper sets. Ever read about people who say they have to fiddle with their needle valve all the time? The higher price, higher quality needle valves have a certain amount of drag built in so that it takes more torque to make them move. The cheaper have less drag and can move when the gas turns on/off. I would look at setting the adjustment for the short term but look at replacing the needle valve is where many do wind up. Two lines drawn on the valve body and the stem may let you see that the stem has moved when things go bad. A bit of superglue on the stem to body joint?
 

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If one cannot blow through CO2 line into the diffuser without regulator hooked up,and without backpressure from diffuser.then I might consider clogged diffuser or as mentioned,,too small a diffuser for pressure your trying to run.
How would one get back pressure otherwise?
 

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I think the issue may be getting confused when we speak of backpressure as the cause. Two things that make me say this. If the situation is changing at times, there would seem to be some item changing to get those results. Is it logical to think the backpressure from a clogged or faulty diffuser would change for the better? Maybe a clue is in the way the situation is cured when the needle valve is adjusted but then returns?
I can't think of any way that backpressure would change but I know cheap needle valves do it all the time.
 

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CO2 Back pressure.

The Milwaukee service advice is not logical! Why would they have a valve AFTER the regulator and the solenoid to constrict flow (thus causing back pressure) with the bubble counter if back pressure was such a problem? And why not have a cheaper release valve instead of a pressure gauge if back pressure was a problem? Plus the only possible problem would be the pressure equalizing on both sides making it simply like a resting state!

I used one of these things for years but when I switched to a canister diffuser I could not get an even flow. Then I stupidly blew up the guage on a tank change by tightening the knob DOWN then opening the CO2 full. I took the whole thing apart trying to fix it, the problem is the gauge is a cheap manual spring type - you can't re-tighten the spring. The knob is simply a needle valve so pressure anyway has no effect. But the needle design means as the CO2 tank empties and loses pressure from emptying the needle regulator will have to be tightened.

So they do want to avoid back pressure but it is not causing anything to "gum up" The problem is tightening everyting up and then opening the CO2 causing the spring in the guage to blow out. A new cannister is 550psi and the guage only goes to 250psi
 

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Can't you just disconnect the line going from the diffuser to the filter. If your CO2 flows properly it's a problem with the filter creating back pressure (I'll be surprised) If it doesn't it's the diffuser or reg.
 
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