New pool - FC & CSI trends?

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KurtinTUS

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Jul 20, 2017
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Tucson
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Couple days since hand-off from the PB. Only additions so far (based on Pool Math) are 1 quart of 29% muriatic acid to bring the pH under control, and yesterday I started a sock with about 3 lbs of dry stabilizer (about 2/3rds dissolved as of this writing.) I'm a little surprised at the recent run-up in FC since it was very low for a number of days before today. Should I start dialing back the IC40? It's currently at 50%. Also the CSI is really plummeting...if I add some calcium chloride to bring up the CH, would that also help out the CSI?

Thanks!

Kurt
 
The biggest influence on your CSI right now would appear to be the acid that is lowering pH and TA. It's normal to attack a rising pH demand with acid, but while your CH is currently low, allowing the pH and TA to float a little higher will help compensate. So for now, I'd allow the pH and TA to be slightly higher so that your CSI doesn't go any lower than about -0.3. You can add some calcium now if you like (min range for your SWG pool is 350), but be cautious about going too high as I suspect your fill water might have a high CH content. As you start topping-off the pool throughout the season, your CH should climb as well. If you add CH, perhaps shoot for an initial target of about 250-300 and let the fill water do the rest.

Hold the phones Kurt! I just saw something else..... why did the CH drop in the past 4 days? That big of a drop would seem to indicate about a 50% water exchange since fresh water is the only way to remove CH short of a RO process. So if that's the same water, there must be a testing irregularity. Which test kit are you using, and do you have the magnetic speed stir? I don't see that in your signature. Before you adjust anything else as I rambled about above, let's make sure that CH reading is really correct.
 
I don't see a heater, so can I assume your water is a bit chilly? That'll do it this time of year. If your water temp is at or below 60, FC loss slows way down. I'm surprised your SWG is even putting-out FC. Normally in the swimming season you would have your CYA at 70 and FC balanced to that number (about 5) on the chlorine chart, but since it's winter and you don't have a high FC demand, you can just let the CYA go to about 30 (unless you added stabilizer for a higher number) and balance FC to that CYA. Looking at the Pool School - Chlorine / CYA Chart page, the ideal target for a pool with a CYA of 30 is an FC of 4-6, so you're fine. Even if your CYA was 70 for a SWG pool, the target is 5, so good either way.
 
Thanks for the info, Pat! Just now realized my screen shot didn't include water temp....it's 58F today and I expect it to remain in close to that for a while. We'll leave the heater off until about March!
 
Kurt,

I run my IC40 at about 50% in the middle of the summer!!! In the Fall and Spring, I run it at "about" 10%.... As Pat says, when the water temperature drops below about 52 degrees, the IC40 will automatically shut off and give you a cold water warning.. My water temp is now 42 degrees and my cell is asleep for the next few months... :p

Thanks,

Jim R.
 
Kurt. In your other thread I mentioned cold water and your SWCG shutting down. I see no way your water will stay warm enough to allow the SWCG run without running the heater. I live in S Nevada and my SWCG shut down 3 weeks ago.

You do not show a heater in your signature but you state you have one. Can you add it to the signature?

If you do run the heater the water exiting the heater may be warm enough to activate the SWCG. But that would be a very expensive way to generate any chlorine you need. Also, the heater should not be run if the pool water is below 68F

Take care
 
Thanks for the info, Jim & Marty! I do have a heater (profile now updated) but we only plan to use it occasionally for the spa until things warm up in the Spring. I'll dial back the SWG to 10% or so and see how that works, as well as keep an eye on the water temp triggering an SWG shutdown....hasn't yet, but we've had a really mild Dec/Jan so far.
 
Just an update:

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So I'm thinking it's probably past time to start addressing the CH. Fill water CH is right at 200 also (all data is from TF100). Pool Math recommends 3 gallons & 1 quart of calcium chloride. Does that sound about right for a 1-month old pool, or should I more gradually ease into raising the CH? Also, anything to be mindful of when adding calcium chloride to a cold pool? Thanks!
 
I am not sure I would add calcium. You are getting some evaporation which will increase a lot in a couple months. That will increase your CH.
Keep your pH in the high 7's and you should be ok.

Take care
 

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Calcium chloride is a solid. So it would be by weight.

To keep you CSI less negative, do not add any acid unless your pH reaches 8. And then only add enough to take it down to 7.8.

When the water warms up in the spring and your CH rises naturally due to evaporation, recommendations will change.

Take care.
 
The pH rises on its own over time because the water out-gasses carbon dioxide into the air. Let pH climb and saturation will become a non-issue for you pretty soon, probably within a few days or maybe a week. The aggressiveness of the water is important, but slowed by the cold water, so there's no rush, other than to let it happen.

Really good to be thinking about though, because the right levels will make your finish stay smooth and last a long time.

Nice to meet you and great idea posting those screenshots from the PoolMath app. Makes it all really easy to see what's what!
 
As a fellow Tucsonan and someone with a plaster pool, let me give you some advice - keep a eye on your saturation index but don't try to manage your calcium. Unless you are someone who has a low CH private or community well (there are some folks in Tucson with wells that put out water with a CH of 50ppm) OR your auto fill or hose bib is tied into a water softener, then you get your water from the Tucson Water Dept. and you get the pleasure of water delivered to your home with a CH of 300ppm on average. Tucson has a Class A Pan Evaporation rate of over 90" of water per year and a rainfall of < 10"/year. What this means is that an average depth (6-7 ft), uncovered pool will evaporate all of its water :)shock:) in one year (or less). You will see this reflected in your CH testing as your pool water CH will rise 200-300ppm per year. This is the reality of living in a desert with a pool.

My water is over 4 years old and the CH is currently >1250ppm. I wouldn't be surprised if, by spring time, when I'm ready to dump my water, it's closer to 1500ppm. Even when my water was near 1000ppm, it was still easy to manage and keep scale away. You simply have to focus on your CSI and keep your saturation levels between 0 and -0.3. Since you have an SWG and because rising pH is always an issue around here, you might want to consider adding borates to your pool water at some point (it's not necessary but it can help) as the addition of borates keeps the pH rise under control and it can protect the SWG cell from scaling.

You're doing well and you're on the right track. Just let your pH and TA ride higher during this winter and your CSI will come down. It takes months and year's worth of aggressive water to ruin pool plaster and, as our esteemed expert on plaster (onBalance) will tell anyone who will listen, water chemistry is rarely, if ever, the cause of plaster issues. Most plaster issues are caused by poor plastering work or simply substandard plaster materials or mixes.

Welcome :wave:
 
I forgot that poolmath gives volume as well as weight measurements for calcium chloride. So, gallons could be a valid measurement. It's just unusual to see it measured that way.

Also, the bulk density of calcium chloride is approximately 1 oz weight per one fluid ounce. So, it would work either way.
 
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