Carbondoser vs. 2-Stage Regulator System: Supply Pressure effect on CO2 flow

[Fish Out of H2O]

I understand that the Carbon Doser works very well for many in the hobby. I personally have never owned or used one. I open this topic as a form of sharing my experience and hoping to learn from the community.

I joined the R2R forum recently for 2 reasons:
1. I have always wanted a SW reef tank and want to learn from your experience before pulling the trigger.
2. As a hobby, I build custom CO2 systems and looking to learn on application to Reef systems.

Reading about the need for precise control of CO2 flow into CR got me thinking about how the Carbon Doser handles supply pressure effect and the potential impact on bubble rate.
Referred to as ‘End of Tank Dump’ (EOTD). EOTD is our hobby’s description of the technical term ‘supply pressure effect. Here is math as it relates to CO2 as PSI can increase/decrease due to temp changes on tank as well as CO2 tank drainage as it empties. Source:
https://northerncal.swagelok.com/bl...o-stage-regulator-s-effect-on-supply-pressure

In a typical (high purity Swagelok) single stage regulator the supply pressure effect may be about 1%, so a 2000 psig decrease in inlet pressure would result in a 20 psig (1% of 2000 psig) increase in outlet pressure.
In a typical two stage regulator, the supply pressure effect is approximately .01%. The 2000 psig decrease in inlet pressure to the first stage regulator would result in a 20 psig (1% of 2000 psig) increase in outlet pressure. That increase would be a 20 psig increase to the inlet of the second stage pressure regulator resulting in a 0.2 psig (1% of 20 psig or .01% of 2000 psig) decrease in outlet pressure.
Translating this information over to real world use of CO2: At 70 degrees F, CO2 tank pressure is 853 psi. A drop in temp to 60 degrees F would drop tank pressure to 747 PSI. The 106 psi drop would translate to 1.06 psi drop from a single stage regulator or a .0106 psi drop from a 2 Stage regulator.
This same math applies as a tank empties if not monitored and replaced as pressure effect is realized.

The Carbon Doser is designed using a simple, brass single stage regulator. Based on looks of the regulator, It appears to be manufactured by Cornelius and is often sold to the beverage industry.
https://fhsteinbart.com/product/double-gauge-regulator-co2-0-60-p-s-i/

I cannot locate the regulator specs on supply pressure effect, but can only assume it would be equal to or greater than the effect of a Swagelok Stainless single stage regulator with a retail price over $600.

As the Carbon Doser controls flow of bubbles using a high quality solenoid opening and closing in fractions of time, I assume the supply pressure increases &/or decreases due to tank pressure or temp changes must affect CO2 precision.

My questions to the community:

Have you experienced effects of supply pressure effect with a 1 Stage Reg or is it negligible?

Does an Apex or alternate source of CO2/PH control offset this in some way.

I don’t pretend to understand all systems and controls in this community, so any and all information is appreciated.

 

[ispookie666]

If using a pH controller the end of tank dump would not matter much. I had this problem in my FW setup using 2 stage reg as well.

I see this often with Nitrous Oxide (joys of working in health care).

 

[Acuario]

I used a CarbonDoser for a year with good results. The pH in my reactor varied typically by about .05 which I controlled with my Apex. However, switching CO2 tanks or probes was not effortless, things had to be reset and retested each time. The CarbonDoser made me nervous too, at least how I ran it, as it depended upon an accurate pH probe measurement in the calcium reactor, so I recalibrated about every three weeks.

Now that I have a two-stage regulator, I have found this system to be more stable with less worry. Bubble-counts are rock solid and not dependent upon electronics other than the solenoid staying open and I can vary the bubble size. (A Burkert solenoid is rated at 1 billion of/off life cycles.) I run this with a Vectra pump and feed the effluent into an ARID reactor, no peristaltic pump. I've been able to lower my effluent rate and increase the tank pH as well. I do see a bit of pH variance in the reactor from day to night.

The image below shows the changeover from Carbondoser to the two-stage regulator on May 25. I'm still learning how to fine-tune this system, but the stability is remarkable. The most recent hour of pH measurements from the calcium reactor are shown by the straight line.

 

[ispookie666]

I could not get why you did put up the isotherms, all it shoes is that the vapor state of CO2 and the Critical pressure. Anyway, nice graph.

 

[Acuario]

Hi ispookie,
From my experience, this is what happens with a single-stage regulator when the CO2 starts to run out and your pH probe is a year old.

 

[Fish Out of H2O]

Thanks for the feedback Acuario- nice detail on before and after! This is what I assumed would be the case.
It appears to come down to just how precise you need the CO2 injection to be for your specific aquarium needs.

 

[Fish Out of H2O]

I recently had a question about comparison of Carbondoser vs 2-Stage Regulator components. Want to share as it applies to this thread on pressure effect:

...My point is not that the Carbondoser is a bad choice for CO2 distribution, it is that you have significantly better options available at a similar price. Their claim to be the best in the world is simple marketing. The single stage regulator used by the Carbondoser is a $60 brass reg that like ALL 1 Stage regs, is subject to supply pressure effect. See photo:

From the reg, CO2 is controlled by the opening and closing of a solenoid through a circuit board. The yellow cap solenoid is a very good quality, Clippard EV Series solenoid, which I use frequently due to low power consumption and reliability.

The average 2-Stage regulator is industrial quality, made for laboratory environments, and will not be affected by supply pressure decreases. Meaning that as PH is monitored, swings in PH should be much closer to your desired setting and much more consistent due to consistent delivery pressure and bubble flow.

These regulators retail for $300-$900 depending on brand. The solenoid is not used to control bubbles, it is simply either on/off. The critical upgrade to a custom system is the addition of a fine metering valve. These valves are what controls bubble flow & are manually controlled by the turning a dial. These valves maintain highest consistency flow from 1 bubble per 5 seconds and up.

Last, I want to clear up a misunderstanding. I’ve read on R2R a recommendation that the only alternative to a Carbondoser is a STAINLESS STEEL 2-Stage system. I strongly disagree- The CD is made of brass and electronic components. With the use of a check valve, water is kept away from the system. A BRASS 2-Stage system offers the same high quality CO2 distribution as a Stainless Steel build. The only difference is looks and how it will hold up if stored in a humid environment or subject to weather as SS will not rust.

 

[mitch91175]

I am on the market for a CO2 regulator and was thinking about the CarbonDoser until reading this. Looking on Amazon, which of these guys would you recommend? Going to use a Geo CR612X2 reactor with a Kamoer FX-STP Calcium Peristaltic Pump. Just in the planing phases ATM.

https://www.amazon.com/s/ref=nb_sb_...lator&rh=i:aps,k:harris+2+stage+co2+regulator

Is there any other regulator that you could recommend that will work better than the CarbonDoser?

 

[Fish Out of H2O]

For the highest consistency and dependability, a 2 Stage regulator with a solenoid & low flow metering valve is the way to go. With time, planning and patience you can buy and build an outstanding system for less than the cost of a CD. There are some great DIY threads out there and I’m happy to be a resource.
If you are looking for prebuilt 2 Stage, there are options out there, but retail on these is pricey from sources like GLA, etc.
There are some great Harris 2 Stage regs listed on that Amazon link at $400-$500 retail but I typically find new regulators for less from overstock sources.
There are a few of us that build and sell systems on flea-bay and through various threads, just make sure you do your research, know exactly what you need and know what you are getting before you buy.
Good luck with your build!

 

[ca1ore]

I've not used the carbon doser myself - certainly it looks fine. I've been using a Milwaukee 2-stage unit for many years. Originally won it in a tank contest; at least 15 years ago ..... perhaps longer. I have not found it to be affected by supply pressure, though the pressure in a CO2 cylinder only changes at the very end once all liquid has gone anyhow. For nominally $100, hard to beat this unit, particularly since it has lasted as long as it has. Some surface corrosion, as one would expect, but fine otherwise.

I have my CaRx setup so that CO2 is dosed continuously to maintain a 6.8 PH. Apex monitors, and alerts me if the PH drops or exceeds 6.8.

 

[Chris155hp]

Awesome thread!!!!

 

[Water Dog]

DIY 2 stage regulators are just plain sexy! Here’s my full stainless Victor 2 stage with liquid filled Wika gauges, Burkert 6011 solenoid and Hoke 1300 series metering valve. Once you familiarize yourself with the different parts, these regulator build projects are really fun!

 

[Sumo]

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[billwill]

As the owner of a two stage regulator with fancy Burkett solenoid and Fabco needle valve, my $0.02 is that the needle valve is the only thing to compare against the carbon doser. If you don’t have the fancy needle valve, it doesn’t matter how fancy your regulator is. The carbon doser metering is more precise than fancy needle valve. End of tank dump, meh. Pay attention to your gage and replace your tank when it’s low; not when your tank crashes. Though I will say I like to brag about my fancy custom made two stage regulator... but I’m as much a gear geek as I am a reefer

 

[Acuario]

I find you can make very minor incremental changes with a needle valve. The big drawback of the Carbondoser is it depends on your pH probe reading, which will drift. I was recalibrating mine every 2–3 weeks to be safe. A two-stage regulator setup with solenoid does not require either a computer controller or a pH probe to work. Of course you can use both to monitor your calcium reactor, send alerts, and keep the pH level within a certain tolerance.
The pH of my calcium reactor varies only by about .08 over the course of a week without using a controller. For even more stability, I know many aquarists use a Cole-Parmer type peristaltic pump for consistent effluent flow, but I have been able to get by on a $10 pinch valve.

 

[billwill]

I find you can make very minor incremental changes with a needle valve. The big drawback of the Carbondoser is it depends on your pH probe reading, which will drift. I was recalibrating mine every 2–3 weeks to be safe. A two-stage regulator setup with solenoid does not require either a computer controller or a pH probe to work. Of course you can use both to monitor your calcium reactor, send alerts, and keep the pH level within a certain tolerance.
The pH of my calcium reactor varies only by about .08 over the course of a week without using a controller. For even more stability, I know many aquarists use a Cole-Parmer type peristaltic pump for consistent effluent flow, but I have been able to get by on a $10 pinch valve.

Not following your logic. Carbon doser simply sets bubbles per minute. Nothing more. That has nothing to do with your ph probe. It also has nothing to do with your effluent output. And a two stage regulator does absolutely nothing different than single stage (carbon doser). Neither of these products is a controller; the carbon doser simply has digital method to control bubble rate vs a fancy needle valve.

 

[Rick.45cal]

I have both a 2 stage regulator and a carbon doser regulator, the 2 stage runs my CaRx, the solenoid is always on, I don’t even care what my bubble count actually is. It’s on a 20lb cyclinder and I haven’t had to make an adjustment in over 8 months now. The carbon doser is still brand new and in the box in my shed. I can’t speak to the carbon doser’s effectiveness because I‘ve never used it.

 

[Acuario]

Yes, you're right Bill. Do you run your Carbondoser without a controller?
My experience is running a Carbondoser with an Apex which required an accurate calcium reactor pH probe reading:

Fallback OFF
Set OFF
If CaR_pH > 6.70 Then ON
If Sys_pH < 7.50 Then OFF
If Output Calc_R_Recir = OFF Then OFF

This requires that your probe be accurate.
Another vulnerability with this setup, besides the probe getting off, is when the Apex fails, as mine did.

Maybe another way to come at this is I measured the dKH of my calcium reactor effluent every day last week multiple times. The effluent dkH varied 4% over the course of the week. The tank dKH varied by 0.5%. Bottom line my corals are happy and I like the reliability. No controller is necessary, things don't get off when the probe changes, and the regulator doesn't go whacko when the CO2 starts to run out.

I suppose one could try a two-stage regulator with the Carbondoser and not use the configurations shown above?

 

[editour2]

I find you can make very minor incremental changes with a needle valve. The big drawback of the Carbondoser is it depends on your pH probe reading, which will drift. I was recalibrating mine every 2–3 weeks to be safe. A two-stage regulator setup with solenoid does not require either a computer controller or a pH probe to work. Of course you can use both to monitor your calcium reactor, send alerts, and keep the pH level within a certain tolerance.
The pH of my calcium reactor varies only by about .08 over the course of a week without using a controller. For even more stability, I know many aquarists use a Cole-Parmer type peristaltic pump for consistent effluent flow, but I have been able to get by on a $10 pinch valve.

I don't fully understand this point. I have a cheap single gauge regulator and am dealing with issues regarding the solenoid remaining open after the ph drops to 6.5. I have my milwaukee ph controller set to turn on the CO2 when the ph raises above 6.7 and turn off when hitting 6.5, [the ph probe is in my calcium reactor]. So the question is why is the carbon doser any different on depending on the ph reading then my current regulator? Aren't they both regulated by the ph reading?

 

[infinite0180]

I always wondered about this..