Poolsmith CO2 injection for pH control

[cptkirk]

Doesn't appear to be much discussion about this system on the forum. Am seriously considering ordering one of these. I'm typically adding about a quart of acid every 3 to 4 days in my 20k gallon SWG pool. Not a lot of fun, plus if we travel for more than a week or so I need to hire someone to keep the pH at a reasonable level. Doesn't seem to be a lot of downside to switching to CO2 injection besides the initial cost. Anyone have any experience with these systems?

 

[aussieta]

as usual
what are your test results and what kit are you using
how old is this pool/fresh replaster?
do you top up pool, what is ta of fill water
i have not added acid for 2 years now, since my ta hit 50

 

[ajw22]

Yeah, it has been discussed over the years. Consider a Stenner pump for acid injection instead.

Prior discussions on CO2 injection...

CO2 Injection

I'd like to start a discussion on CO2 injection. It seems it is often quickly shot down whenever it is brought up here for a number of different reasons but the discussion never goes very far. I think I'm in a slightly different situation where it would normally be ridiculous for me to even...

www.troublefreepool.com

My experience with CO2

I built a CO2 system and used it for a couple of years. I used my home automation to time the injection. In fact I still have a 20lb CO2 bottle that is empty. In my experience it didn't work out too well. I live in AZ and it gets hot here. The CO2 bottles are under very high pressure and if...

www.troublefreepool.com

You may want to read...
Pool Tip #18: Use of Carbon Dioxide for pH Control | Aquatic Consulting Services

Google search results

www.troublefreepool.com

 

[YippeeSkippy]

Kinda wondering *why* your pool needs so much acid?? Do you run a lot of spill over spa, bubblers, fountains?? New plaster still curing??

Can you give us some test result so we can check to see if we see a problem?
FC
CC
pH
TA
CH
CYA
Salt if applicable

Maddie

 

[cptkirk]

Had seen most of the discussion that was linked above except for the one from the person who constructed their own system in AZ. It's interesting because the Poolsmith folks are based in Phoenix and claim to have around 500 systems in the field. I don't think I would have most of these issues since summer is not as brutal where I am. Also the injection method is different than what is described (Poolsmith injects at the filter pump) and CO2 usage is claimed to be less. For me it's not so much about saving money as it is about convenience and avoiding handling acid as much as I have to now. Acid injection makes me a bit nervous since a malfunction could be bad news. CO2 seems a bit more forgiving.

 

[cptkirk]

Ideally I'm looking for feedback from anyone who has used this specific system. Of course the testimonials on the Poolsmith website are all going to be good, and if I ask them for references they will all be good too.

 

[red-beard]

I'm thinking of a similar system. I have a very small spillover from the spa, but the drop is only 3 inches or so. But I have wind. Lots of wind. My TA is around 80. My pool will go from 7.5 to 7.8 in about a week. I add about a quart to 1/2 gallon of acid a week. Pool and plaster is 14 years old.

I have an "Ozone" injection line. I am thinking of getting 80 lbs tanks from a welding supply shop. The regulator is the main issue. It will require 2 regulators, one to drop the pressure and the other to be a flow regulator. Joyful Noise had some ideas on how to calculate to CO2 loss pH rise. And CO2 is cheap.

It will not be an automated system. It will be more like the SWCG. Adjust the flow and see how the pH responds. It will definitely be temperature dependent, since CO2 solubility shift with temperature.

 

[mknauss]

Do realize that CO2 injection does not effect TA. So you will still need to use acid to manage TA.

 

[cptkirk]

The Poolsmith system doesn't use sensors. Basically you dial in how long you want injection to occur and what the flow volume is. They give you some starting parameters based on size of the pool, then you tweak up or down as your particular pool requires to achieve your target pH. Since my pool operating conditions in season are relatively constant, I would *think* this kind of set up would work well for me.

Don't have a good feel for how fast TA would climb since I'm adding acid so frequently. I don't know what the TA of the pool fill water is, will try to test that. It's not so easy because all the water taps I have access to go through a whole-home filter/softener first but the pool fill does not. But if other variables are constant or nearly so, it appears I could tolerate a fairly broad range of TA and still be within reasonable balance.

 

[mknauss]

Water softener's do not remove TA

 

[cptkirk]

Going back to the post asking about my specific pool. 20k gallons, plaster, about 3.5 years old, outdoors but screened in, SWG, with autofill. I have 6 deck jets, but typically these are only run one day a week for 15 minutes just to exercise the pump a little. No other water features or spa. Here are my numbers from testing this morning:

CL: 3 ppm (no CC)
pH: 7.8
Alk: 80 ppm
Ca: 310 ppm
Salt: 2900 ppm
CYA: 30 ppm

I know the CYA is much lower than recommended here, but my CL is well controlled at this level. Currently I'm only running the SWG from 10am to 3pm at 10%, but we're not using the pool yet. After we start using the pool in a week or so, I'll up that to around 8 hours, probably will up the percentage to 15% once it gets hotter. I run my filter pump continuously at 50%. I have tried running the system with Alk down at 60 ppm, but it didn't seem to make a lot of difference on my acid demand.

I did test the fill water by putting my filter/softener into bypass and drawing some water from an outdoor faucet near the water inlet after flushing it for a minute or so. CL was 1.2 ppm, ph 7.8, Alk 70, Ca 90. I have not noticed Ca creeping up (if anything I have to add some occasionally after we get a hard rain), and this tends to be a fairly humid area, so I don't think the fill has a big impact normally.

 

[Katodude]

Get an electronic pH meter (one of the good ones that @setsailsoon) uses. Use that to drop you TA down to 60 and you pH level should stabilize. I find that since I got a pH meter I understand how my pH rises and falls much more accurately than the drop test. I used to have to add acid every 2 days and now I am down to once a week. Once we start using the pool more this spring I will try to refine that even more.

Then when you travel throw a few pucks in a floater and you are all set.

 

[JoyfulNoise]

There really isn’t anything wrong with using CO2 injection other than the additional plumbing and hardware needed at the pad. It adds more to the equipment maintenance side of pool ownership. The biggest hassle is CO2 tank exchanges. I’m some areas it’s cheap & easy. In other areas you have to rely on expensive delivery services. My guess is there will be little cost savings between adding acid manually or injecting CO2. Once you get a feel for usage and CO2 demand, you’ll get a clearer picture of the annual cost. You may want to use it in the swim season and then go back to manual addition over winter. Believe me, I understand the hassle of adding acid but it gets better over time. Initially my pool drank acid like it was KoolAid, now I’m adding acid every 7–10 days in the summer and weeks apart in the winter (I think I went over a month between my last additions). Your pool will settle in too.

Good luck and let us now how the system performs.

 

[cptkirk]

I decided to get the Poolsmith system, should be arriving next week. After I get it installed and have a little experience with it, I will post about it.

 

[Prickly]

I just ordered the Hayward CO2 Sense and Dispense system. I haven't personally used CO2 but I am a former Public Health Inspector and have seen them in use in a couple pools that I inspected. The operators loved them because it kept a steady pH of 7.4 while allowing them to maintain the required 80-120 ppm TA. This isn't easy to achieve with acid because the pH will want to stay much higher with that TA. I realize that most people resort to keeping a lower TA in order to prevent the pH rise but my fiberglass pool manufacturer has advised that a lower TA will harm the gel coat. I have witnessed this in my pool when I kept a low TA and the coat developed a temporary white haze that immediately resolved when the TA increased. The unit cost me $611 in Canada and I believe it goes for $300 ish in the USA.

 

[cptkirk]

Finished the installation of the Poolsmith system yesterday. Below are a few pictures.

The first picture is of the controller. The connections to the pool equipment are at the bottom from left to right: power cable; CO2 input from tanks; CO2 output to pump; water pressure input from pump. Schematically, the system is pretty simple. The CO2 input first goes into a flow meter on the left. The knob at the bottom of the meter is used to control the flow rate. From the top of the meter, the gas flows through a relay that is controlled by a timer circuit. The dials labeled "INPHUSION SETTING" on the right control the length of time gas will be injected. During the injection interval, gas is injected periodically (2 minutes on, then 2 minutes off). The green LED shows when you have power. The yellow LED shows when injection is occurring. The water pressure input is provided so that the system will not inject if the pump is not running.



The second picture show three 20lb. CO2 tanks in a small shelter I built to keep them out of direct sunlight. The tanks are ganged together and run through a single tube which I threaded through some flexible conduit to the controller. I didn't have room for the tanks immediately adjacent to the controller, so they are about 25 feet away.



The third picture shows the connections to the filter pump from the controller. The gas is injected through the right drain port (under the pump skimmer basket). The left drain port (on the impeller side of the pump) runs to the pressure sensor on the controller.



Continued on next post.

 

[cptkirk]

When I first turned the system on, gas was not flowing through the meter, even though I verified that gas was being supplied to the controller input. Poolsmith is a small company, and I was able to immediately get in touch with the owner. We walked through some basic diagnostics (just to make sure I hadn't made some mistake in installation), and he concluded that the problem was inside the controller and agreed to send me a new unit, which he shipped out later that same day.

A couple of hours later when I had some time, I decided to pop the front cover off to see if there was anything obviously wrong. Sure enough, the short tube that connects the flow meter to the relay had gotten crimped, probably during final assembly. The internal tubing is identical to the external tubing, so I was able to remove the damaged tubing and replace with a short length cut from the external tubing that is part of the kit, and voila it worked.

I have initially set the flow rate and timer settings to the values recommended for my size pool, and we'll see what happens. I will periodically add new posts with my observations on performance.

 

[JoyfulNoise]

What’s your cost for CO2 in your area?

 

[cptkirk]

It's not cheap. There are not a lot of options for refill. Cheapest I've found near me is $45 each, but I found another company that will do a tank exchange for $25. I'm not expecting to save money, it's more about not having to handle acid so often, and to be able to go away for a couple of weeks without having to hire someone to keep things in balance.

 

[JoyfulNoise]

It's not cheap. There are not a lot of options for refill. Cheapest I've found near me is $45 each, but I found another company that will do a tank exchange for $25. I'm not expecting to save money, it's more about not having to handle acid so often, and to be able to go away for a couple of weeks without having to hire someone to keep things in balance.

I haven’t looked around my area fir pricing but I wouldn’t be surprised if it were as expensive. Welding supply shops are probably the cheapest source but you usually have to buy big tanks. Hopefully you can get a lot of use out of those three tanks before you need to exchange.

If you control your aeration sources and keep the pool covered, you won’t use much CO2. pH control is all about outgassing of CO2. The better you control that, the less fiddling with pH is required.