The fastest injection rate at 20 GPM of water flow is about 0.26 lb per minute CO2 to avoid oversaturating the water.
DIY PH measurement and CO2 Injection System- Project Summary
- Thread starter setsailsoon
- Start date
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
I've definitely found I need more than the free version of ChatGPT so I pay a monthly fee. I've used it to write a very simple pool control and replacement for my Rainbird that bit the dust early using ESP32. Nowhere near as powerful as the RPi devices but also only $6 or so for the chip. Had to add a relay board but total on parts was less than $20. I did a little surgery on the Rainbird box and easily fit the 5v power supply, ESP 32 and 8 ch relay board inside. Plus, I really hated the Rainbird phone interface software - very clunky. Looking forward to try Claude. Also, loving the fact this old guy that last wrote software in Fortran almost 50 years ago now can get ChatGPT to write it and I just have to tweak it a little but it works.
Chris
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
That is very, very helpful. Thanks much! I think all I need is about 1.5 # per day but this is very rough approximation.
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Flow rate is about 25 gpm but I can raise/lower with the vs pump. Injection rate of CO2 is .05 lb per sec.
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
There are a lot of things I need to play around with to verify this is a long term solution but at least for short term like 3 wk absence I think this is going to help me keep my new pool plaster within TFP recommendations for pH. And being able to monitor/control on the internet is really not that hard to do. I did a little test to see how long the pool can stay within spec if I take pH down to ~7.1 without adding any acid. Less than 3 days I was at 8! So I'm not real happy going for another couple weeks. Admittedly, one two week excursion isn't the worst thing in the world. But I've gotten a little anal about TFP recommendations. They've served me very well since 2015.
Chris
Chris
That's 3 lb per minute, so it seems a little high to me, but I don't really know for sure how much can be added efficiently.
I am just using calculations based on the chemistry.
1.25 grams per liter = 0.01043176 lb per gallon at 86 degrees F (30 C).
1.3 lb can be dissolved in 125 Gallons.
At 25 GPM, 1.3 lb can be injected in about 5 minutes.
The max injection should be about 0.26 lb per minute or about 0.004 lb per second.
That is 1.3 lb in 26 seconds.
Are you sure that that is the rate?
Is it 0.05 oz per second?
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
I'm assuming choke flow through the 1/4" tubing. 2.83#/min. .047#/sec It is actually a little less than this but not much (I neglected to deduct wall thickness in the cross sectional area).
In my opinion, that is way too fast and most will not dissolve.
How did you get that target feed rate?
9.15 lb/hr = 0.1525 lb/minute = 0.00254 lb/sec.
CO2 Feed System - Blue-White Industries
Simple design allows safe and effective pH control. The CO2 Feed System maintains the desired pH level by directly injecting carbon dioxide into the water supply. This process creates carbonic acid, which lowers the water’s pH level naturally without hazardous chemicals such as sodium bisulfate...
www.blue-white.com
The density of carbon dioxide gas is listed as 0.1144 lb/ft³ at 70°F and 1 atmosphere pressure.
The typical feed rate for pool carbon dioxide (CO2) is usually expressed in "SCFH" (standard cubic feet per hour) and can range from 0-30 SCFH depending on the pool size and desired pH level, with most residential pools requiring a feed rate between 5-20 SCFH.
By implementing our Nano / Ultra-Fine Bubble (UFB) Technology, the pHure Feed Skid system diffuses 683 million Nano / Ultra-Fine Bubbles and has a staggering 97% to 100% efficiency.
The pHure Feed is the only NSF certified carbon dioxide Nano diffusing system.
This feeder is designed to operate at 130 SCFH and Maximum inlet pressure of 40 PSI / Ideal Flow Rate 55 – 85 GPM.
Maximum working pressure: 50 PSI
130 SCFH x 0.1144 lb/ft³ = 14.87 lb/hr at 55 gpm = 0.25 lb/minute = 0.004 lb/second.
The typical feed rate for pool carbon dioxide (CO2) is usually expressed in "SCFH" (standard cubic feet per hour) and can range from 0-30 SCFH depending on the pool size and desired pH level, with most residential pools requiring a feed rate between 5-20 SCFH.
By implementing our Nano / Ultra-Fine Bubble (UFB) Technology, the pHure Feed Skid system diffuses 683 million Nano / Ultra-Fine Bubbles and has a staggering 97% to 100% efficiency.
The pHure Feed is the only NSF certified carbon dioxide Nano diffusing system.
This feeder is designed to operate at 130 SCFH and Maximum inlet pressure of 40 PSI / Ideal Flow Rate 55 – 85 GPM.
Maximum working pressure: 50 PSI
130 SCFH x 0.1144 lb/ft³ = 14.87 lb/hr at 55 gpm = 0.25 lb/minute = 0.004 lb/second.
Last edited:
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
Interesting. Their start up manual says to start with 15 SCFH which I calculate to be ~1.7#/D. No discussion about how pool size impacts this but at least it's in the ballpark of calculations and matches up pretty closely with the CO2 equivalent of my muriatic acid consumption.
3. Adjust the Rate of Flow knob on the feeder counterclockwise until the flowmeter shows a rate of approximately 15 SCFH (Standard Cubic Feet per Hour).
15 SCFH (Standard Cubic Feet per Hour) is 0.25 cubic feet per minute (0.25 x 0.1144 lb/ft³ = 0.0286lb) = 0.000477 lb per second.
Your rate is 100 times this amount.
Do you have a Diffuser and Eductor?
How are you determining the feed rate of your system?
knorrsystems.com
15 SCFH (Standard Cubic Feet per Hour) is 0.25 cubic feet per minute (0.25 x 0.1144 lb/ft³ = 0.0286lb) = 0.000477 lb per second.
Your rate is 100 times this amount.
Do you have a Diffuser and Eductor?
How are you determining the feed rate of your system?
Product Manuals
Providing equipment, service, training and daily operations for the best aquatic facilities in the United States. Daily, our employees are at pools from Seattle to San Diego, from Houston to Tulsa. We haven't seen it all, but we've seen a lot! We bring this depth of experience to each and every...
With proper injection, the efficiency should be over 90%, but your rate is way too high and the efficiency is probably below 10%.
If you can keep the Carbon Dioxide Level below 1 ppm, that should minimize the loss of CO2.
I would keep the pH at 8.0 to 8.3 to keep the CO2 level as low as possible.
.047#/sec is 10 times too high.
What is the calculation?
You can't compare CO2 directly to muriatic acid.
You need to know if the pH rise is due to CO2 loss and/or to plaster loss.
CO2 loss results in pH rise with no TA or calcium hardness rise.
Plaster loss results in pH, TA and CH rise.
What is happening with the TA and CH over time?
- Oct 25, 2015
- 5,809
- Pool Size
- 28000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
My system is pretty basic at the moment. Flow is only limited by choke flow rate in 1/4" tube. I will add an orifice to limit by a factor of 10. TA has been reducing since refill with well water several months ago. Latest readings have been about 80. I'll check the fill water later today. I add about 60 gal/day due to evaporation. Last two CH readings have been right at min (250 ppm) which is the same as the fill water - pretty hard Florida well water.
That is with a controller that starts and stops the flow based on the pH.
It is not a continuous flow.
The CO2 loss rate depends on the pool surface area, aeration like waterfalls and infinity edges and how much you are over the equilibrium concentration.
If you are 10 time the equilibrium level, then the loss will be much higher than if you were only twice as high as the equilibrium level.
I a do not know if it is a simple linear relationship or an exponential relationship.
If the loss rate at (CO2 PPM Actual/CO2 PPM Equilibrium = 2) is 100 units, then the loss rate at (CO2 PPM Actual/CO2 PPM Equilibrium = 10) will probably be at least 5 times higher and maybe a lot higher.
At (CO2 PPM Actual/CO2 PPM Equilibrium = 1) the loss rate will be zero and the loss rate will begin at some point over 1.0.
Maybe you can do some data logging to see what the loss rates are.
CO2 PPM Actual..............................Loss rate
/CO2 PPM Equilibrium
1..................................................................0.
2..................................................................
3..................................................................
4..................................................................
5..................................................................
6..................................................................
7..................................................................
8..................................................................
9..................................................................
10..................................................................
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Can you keep the pH at 8.3 with a good CSI?
That would minimize the loss of CO2.
You should use a diffuser and keep the injection as slow as possible.
I would inject continuously at the lowest rate possible.
For example, at 1 lb per day, that is 0.04 lb/hr, 0.0007 lb per minute and 0.00001157 lb per second.
That would minimize the loss of CO2.
You should use a diffuser and keep the injection as slow as possible.
I would inject continuously at the lowest rate possible.
For example, at 1 lb per day, that is 0.04 lb/hr, 0.0007 lb per minute and 0.00001157 lb per second.
That is 1.72 lb per hour or 41.184 lb per day.
Pool CO2 Injection System Status
Current pH: 8.65
Target pH: 7.40
Injection State: ON
Time Remaining for Injection: 1 hours, 35 minutes
Current Time (UTC-5): 09:14:58 AM
Turn Injection On (Manual Override)
Set Target pH: 7.40
___________________________________________________
Pool CO2 Injection System Status
Current pH: 7.00
Target pH: 7.40
Injection State: OFF
Mixing Delay: 23.000 hours
Choked Flow Differential Pressure: 136.3 kPa (19.8 psi)
Current Time (UTC-5): 06:49:46 AM
Estimated CO2 Added per Day: 2.95 lbs/day
Manual Control
Mode: Manual
Manual Pulse Length: 1.0 minutes
Start New Injection Pulse
Set Manual Pulse Length (min): 1.0
Set Target pH: 7.40
Set Mixing Delay (hrs): 23.000
Firmware Version: 1.0.0
___________________________________________________
Current pH: 8.65
Target pH: 7.40
How sure are you about the pH at 8.65?
Are you verifying with a separate meter?
A target pH of 7.4 to way too low and it will use way too much CO2.
A target pH of 8.0 to 8.3 will be much more efficient.
___________________________________________________
Current pH: 7.00
Target pH: 7.40
How did the pH get down to 7.0?
___________________________________________________
3.67 lbs CO2 is equal to adding 1 gallon of acid as far as lowering the pH.
Estimated CO2 Added per Day: 2.95 lbs/day
That is about equal to adding 103 oz of muriatic acid per day.
That seems like a lot.
Current pH: 8.65
Target pH: 7.40
Injection State: ON
Time Remaining for Injection: 1 hours, 35 minutes
Current Time (UTC-5): 09:14:58 AM
Turn Injection On (Manual Override)
Set Target pH: 7.40
___________________________________________________
Pool CO2 Injection System Status
Current pH: 7.00
Target pH: 7.40
Injection State: OFF
Mixing Delay: 23.000 hours
Choked Flow Differential Pressure: 136.3 kPa (19.8 psi)
Current Time (UTC-5): 06:49:46 AM
Estimated CO2 Added per Day: 2.95 lbs/day
Manual Control
Mode: Manual
Manual Pulse Length: 1.0 minutes
Start New Injection Pulse
Set Manual Pulse Length (min): 1.0
Set Target pH: 7.40
Set Mixing Delay (hrs): 23.000
Firmware Version: 1.0.0
___________________________________________________
Current pH: 8.65
Target pH: 7.40
How sure are you about the pH at 8.65?
Are you verifying with a separate meter?
A target pH of 7.4 to way too low and it will use way too much CO2.
A target pH of 8.0 to 8.3 will be much more efficient.
___________________________________________________
Current pH: 7.00
Target pH: 7.40
How did the pH get down to 7.0?
___________________________________________________
3.67 lbs CO2 is equal to adding 1 gallon of acid as far as lowering the pH.
Estimated CO2 Added per Day: 2.95 lbs/day
That is about equal to adding 103 oz of muriatic acid per day.
That seems like a lot.