Folks,
Unplanned spare time from construction is a good thing sometimes. Learning/preparing for my RPi set up is invaluable... I also have time for a few other related items like getting my 10K thermocouples and fittings to install them into proper thermowells like
@Katodude did. Much better installation in my opinion but there are some details that need to be addressed not so obvious at first. I think I have that addressed and if anybody wants details let me know.
Next up on my "to-do" list was CO2 injection. Seems like there's a lot of negativity about that for good reasons. But that was the same for salt pools and things have changed somewhat. First thing I do is try to get the facts and for pool chemistry we have great access to experts.
@JoyfulNoise and
@JamesW have left a trail of great information that I'm still getting my arms around. Matt actually referenced a post from James that has been invaluable:
3.67 lbs CO2 is equal to adding 1 gallon of acid as far as lowering the pH.
Edit: It depends on the final target pH. For a target pH of 7.8, you need 3.8 lbs CO2. For a target pH of 7.5, you need 3.9 lbs CO2. For a target pH of 7.0, you need 4.49 lbs CO2 to match the pH drop of one gallon of 31.45% muriatic acid.
For example, with a TA of 110, you need 26 oz acid to lower the pH from 7.8 to 7.5. That's equivalent to 0.79 lb or 12.68 oz (weight) CO2.
Also, that's at 100% of the carbon dioxide getting dissolved into the water.
If the injection process is not good, you might have low efficiency in transfer, which will cause you to use more.
I always try to work the simple stuff first. Is it available for retail? First I called one of the large CO2 vendors for soft drink machines. Answer was easy "NO CAN DO". The only other source I could find was welding gas supplier. Answer there much different, "don't do it a lot but more and more are doing it and yes we can supply your needs with refilling".
So next issue is will it work. Technically I think the experts say it will. But it's a little more complicated since CO2 does not reduce TA like acid does. And it takes more CO2 to lower pH compared to acid depending on how low you want to maintain pH. So now it's getting a little more complicated. But it still appears that if I run my pH on the high end (I always did that with 7.8-8.0 range and it worked well). I will need ~3.8#/CO2 for every gallon of muriatic acid. Then there's the non-technical will it work? Seems like other's experience was that starting and stopping flow systems was the biggest issue here. I plan to run my monster 5 hp pump 24/7 and I would think this should be easier to keep constant flow of CO2. So I think I pass that part to make this worthwhile.
Last is operating cost. My new pool is over 2x my previous pool size so this is more important. The up front cost for a 50# tank varies a lot but seems like $150 is common. Then there's the injection system - they run around $1200. Don't know if I want to spend that much because I don't really need a lot of flow regulation. I can just set the flow rate through a roto-meter and have a high pH range that shuts the system down if anything gets messed up (pretty easy on my RPi to configure this). Once I get the proper amount of flow I should have great control over pH. So long as this system is about the same cost as acid and it works I much prefer it. I hate jug-lugging acid. Just like I hated jug-lugging chlorine. This is certainly a personal preference thing but for me tie goes to CO2... lugging 50# cylinders may get old too but not too bad with my dolly straight out to the pad from the car and 2 cylinders should last several months at least. Cost per # turns out to be a big advantage to CO2. Previous articles indicated it was about equivilent. The sellers of injection systems say CO2 is 20%. I'm finding CO2 is $.92/# so 3.8# is a little less than $3.50. Latest cost for acid is about $9/gal. (wow! that used to be $5-6).
Jury's still out on this but at least it's definitely doable, and cost effective if I install my simple way. Not sure how much TA I'll have to deal with and that will require acid but things are looking positive. My prior pool I had no trouble keeping TA 50-70 but I was adding acid also.
As always suggestions and comments welcome.
Chris
EDIT *** PS I made no attempt to price search for CO2 or acid. Just googled and called one supplier for CO2 since I've never bought that before.
