Chemical Balance Issues for 8+ months?

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Girl_Style

Girl_Style

0
Jul 20, 2015
36
San Diego, CA
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
During the start up of our pool (after resurfacing) you all helped me understand my CH & pH were going to be off for a few months due to the water in so cal + new plaster curing. It's now been over 8 months and I got the numbers to climb into a normal range toward the mid-end of summer and they stayed consistent for a month or so but have continued to climb since and I can't seem to stop the rise.

I did buy the taylor salt test kit :testkit: recommended by this group and have been using it for a month or so but am not positive on how to interpret the numbers and if they mean anything. Any knowledge on that would be awesome :scratch:

It's as if we are shocking our pool consistently so I suppose it could be worse since we won't be growing any mold or algae but I'd like to get them within a normal range for long term if you could help me at all with some thoughts/ideas? :brickwall:

Today's Readings:
pH: 8.2
FC: 21 (I can't believe this but it just keeps going up)
TA: 110
CYA: 70 (the only consistently normal reading we've had)
CH: 500
Sodium Test: 3,400ppm (17 drops)
*I added about 1/4 jug acid like normal but it doesn't seem to be having much effect.
*The salt generator has been turned down to try and knock the chlorine levels down but it doesn't seem to have any effect.
*We have only added 1/2 bag of salt since starting the pool up and that was toward the summer when the chlorine levels dipped for a few weeks.
 
Its likely your pH is well above 8.2. That is the maximum the test reads so it is very possible it is above that. Maybe add about 15 oz of acid, circulate and recheck the pH. Keep doing that until you get to around 7.6 or so.

This time of year, there is much less UV light so little chlorine is being consumed by the sun. I'd recommend shutting the cell down entirely until the chlorine levels drop to normal ranges (this could take several weeks).

Your CH level will continue to rise due to evaporation and refill. Your fill water is more than likely very high in CH, TA, and pH and that is why you are facing a constant rise. Since your CH level is and will be much above the recommended levels, you will need to get familiar with the Calcite Saturation Index and adjust your water accordingly to prevent scale formation.

Your acid additions also add chloride to the water which shows up as salt in the K-1766 test. Each gallon of acid you add will add around 25ppm of salt.

Hopefully el niño pans out this year and you (and the rest of us) get enough rainfall to lower our calcium and salt levels. try to capture all the rain water you can and add it to the pool.
 
Tiptoeadventures said:
Today's Readings:
pH: 8.2
FC: 21 (I can't believe this but it just keeps going up)
TA: 110
CYA: 70 (the only consistently normal reading we've had)
CH: 500
Sodium Test: 3,400ppm (17 drops)
*I added about 1/4 jug acid like normal but it doesn't seem to be having much effect.
*The salt generator has been turned down to try and knock the chlorine levels down but it doesn't seem to have any effect.
*We have only added 1/2 bag of salt since starting the pool up and that was toward the summer when the chlorine levels dipped for a few weeks.
Click to expand...

A couple of thoughts -

pH & TA

You need to bring these under control. As bdavis466 said, your pH is likely a lot higher than 8.2. Unfortunately the TF-100 does not have acid demand drops with it like the Taylor K-2006 as those are useful in a situation like this for telling you how much acid you'll need to add to get down to a specific pH range. PoolMath does this but I find the visual color change of the acid demand test to be very helpful. With that said, your TA (the carbonate alkalinity portion of it) is driving your pH up as well as the lower temperatures this time of year (decreasing water temperatures cause pH to increase). So you need to keep adding acid until you get your pH down. You also need to lower your TA using the acid/aeration method as that is the biggest contributor to your pH rise right now.

FC and SWG

Again, bdavis466 said this but I will repeat, at this time of the year your water is so cold and the UV from the sun is so low (as well as no bather load) that your FC has nothing to react with. Therefore your high FC will take time to come down. If your water is below 58F, then your IC-40 will not generate chlorine as there is a cold water cutoff function to protect the cell. IN the winter time, it is often easier to just shut off the SWG completely (some people remove them and install a dummy cell) and use manual chlorination. Keep monitoring your FC and let it come down naturally.

Salt

Please do not add any salt to your pool unless you have a significant water exchange (rain overflow or partial drain). Salt does not get used up. It does not go away unless you flush water out of your pool. Almost everything you add to your pool (bleach, acid, etc) eventual adds chloride (Cl-) to your water. You SWG does not measure salinity or chloride ion concentration, it measures the conductivity of the water and assumes that the conductivity is related to salt level changes. Most SWG's are not temperature compensated so, when the water temperatures drop, so does the conductivity of the water and the cell reports that as a lower "salt" level. It is not. Trust your K-1766 measurements.

As well, if your chlorine output from the cell as measured by FC seems to drop during the summer months, this is not because the pool water lacks salt. It is typically due to higher bather loads and possible algae growth. If you should experience an algae outbreak due to your FC dropping too low, your SWG will not be able to keep up with the FC demand and your FC will drop no matter how high you set your SWG output. Because algae blooms don't necessarily turn pool water green at first, people often mistake this drop in FC as a chlorine output problem from the cell and think they need to add salt. That is the wrong thing to do. Always check FC/CC regularly and, if you are experiencing a major drop in FC, you should perform an overnight chlorine loss test (OCLT) to determine if the demand requires a SLAM.
 
You are on the right track in testing and understanding your water chemistry. Brian has given you a great response.

I would like to emphasize a couple of points.

As the temps drop and there is less sun you need to lower the output of your SWG. At some point the water will be too cold for the SWG to make chlorine anymore and they often report false low salt errors due to low water temp. Mine starts acting weird as the temps drop below 70. I have already shut mine off and switched to bleach.
It is important to keep PH at 7.8 or less.
Use poolmath to keep your CSI slightly negative to manage your water hardness.
 
and have been using it for a month or so but am not positive on how to interpret the numbers and if they mean anything.
Click to expand...
Then your mission should be to read "The ABC's of Pool Water Chemistry" up in Pool School. There is no point to testing until you understand what you are testing for and what the results mean........that one brief article explains it all.
 
Just my thoughts on a quick start guide:

#1 - Turn the SWG off. - and check your chlorine daily.

#2 - Once the chlorine is below 10 ppm, then bring the pH in line.

#3 -Then lower your TA to more reasonable levels.

What troubles me is that things are "just happening." If you aren't changing your chemistry by putting stuff into the pool, yourself, you (1) have a maladjusted (or broken) SWG and/or (2) the new plaster is a chemical donor, and/or (3) you have a mischievous neighbor. In short, it can't "just happen" and the causes need to be discovered, before harm is done.
 
You all do such a wonderful job of putting my mind at ease :) Thank you for all the helpful advice!!! I will shut the SWG off for the winter (wasn't sure if I should ever do that or not) and change the schedule to slow down the pump run time. We aren't using the pool now because it's so cold and still need to get the igniter fixed in our gas heater for the spa and pool...so no winter use this year means it's a perfect time for me to get the numbers under control.

Need to head to the pool store and restock acid but I'm understanding that I should wait until the FC levels lower until I start adding more acid to lower the ph, correct?

Should I continue to add my normal amount of acid and just increase once the ph normalizes?

Can I help the FC to drop in any other way besides shutting off the SWG & lowering pump run time?

*I will checkout the pool school water testing article again for info on the salt drop test- I thought I had re read it when we got it and was still confused but I'll see What was confusing me and ask a more detailed question if it still slipping over my head ;)
 

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On determining if adding acid is needed we need to know what the pH is measuring now and what the FC level is at. With newer plaster and the SWG was still running, the pool more than likely needs some acid but I would wait until the FC nears 10ppm before adding the acid.

The answer if you should lower the FC level depends on how high it is now and how much it loses in a day with the SWG off. You could add Sodium Thiosulfate to the water to reduce the FC and get back into range today, but it might be a waste of money if the FC is low enough already.

If you don't have automation to control the IC40 then you will need to turn off the SWG in November each year. The lowest setting on the IC40 is 20% without automation and that will generate too much chlorine for your pool. With automation you could lower the output down to 5% with a short run time of a few hours to keep the FC level down.

During the winter I would switch the run time to 3-5 hours with a pump speed of about 1000 RPMs. For the chlorine source add bleach when needed.
 
Sorry! For some reason my email notifications aren't coming through for replies to my posts here.

todays readings made me do a happy dance...for the first time ever I'm in a normal range for most chemicals...thanks to this post and changing the pump run time & checking out the SWG percentage (you were right..it had already shut off on its own due to the water temp being so low)

today:
pH: 7.8
TA: 70
CYA: 80
CH: 450
FC: 13.5 (still working on knocking this down slowly)
Sodium: 3,400ppm

*I just had to give a huge shoutout thank you to all of you for your AMAZING knowledge and help in obtaining these levels today too :)
http://www.troublefreepool.com/threads/108871-THANK-YOU-amp-Good-News
 
bdavis466 said:
I'd let the chlorine come down on its own. No need to persuade it.

Where is your chlorine level now?
Click to expand...

its slowly getting better! The other readings have leveled out beautifully since changing the pump run time.
today:
pH: 7.8
TA: 70
CYA: 80
CH: 450
FC: 13.5 (still working on knocking this down slowly)
Sodium: 3,400ppm
 
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