Help! High CYA/Switching to this from pool store testing and chemocals

mgtfp

Bronze Supporter
Mar 5, 2020
409
Melbourne, Australia
... and just to make sure that I get the times right, not sure if they are shown to me by the system as your local times or my local times. Do the times below look familiar to you, or do they look like they were translated into Australian times?

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mgtfp

Bronze Supporter
Mar 5, 2020
409
Melbourne, Australia
OK, yesterday morning you were at 18ppm and in the evening you were also at 18ppm, right?. In-between, you added 45+45+67 oz of 12% bleach, which for your 22k gal pool should be equivalent to about 7ppm FC, i.e. you had a daytime loss of 7ppm. After passing the OCLT, it should be rather lower than higher now. You can also afford to get down to target FC now.

I would say, let your dad add 5ppm worth of bleach each day, that would be about 112oz. To make it easier, just call 1 gallon, that would be closer to 6ppm of FC. Once your FC gets lower, the absolute FC loss per day should get lower, adding 6ppm worth of bleach should not let FC drop below target while you are away, but it should also not bring it above SLAM I'd say.

Once you're back, you can adjust your bleach additions to get to target level.
 

Ilovemylife1129

Well-known member
Aug 7, 2018
63
Canonsburg/PA
Ok so I think I get what you are saying. Have my Dad add a gallon a day to keep it close to SLAM level while I’m away just to not reverse what I accomplished!!! How did you figure out the 112oz a day is 5ppm? I guess I do t get the math and I want to understand as much as I can. And thank you so much to everyone for your help and time!
 

mgtfp

Bronze Supporter
Mar 5, 2020
409
Melbourne, Australia
I used PoolMath for that. In the Burger Menu at the top left you'll find "Effects of Adding". Enter your pool volume, chose "Bleach" under "Chemical Additions" and set the "bleach Percentage" to 12.5 and enter the amount of bleach to be added. 112oz will result in an FC change of 5ppm.

I am a bit confused about the quart you added at 10:45. I am not too familiar with the US units. 1 quart is 32oz, right? According to PoolMath it should have raised your FC by 1.4ppm. I'm a bit surprised that that got you from 15ppm to 19ppm, according to Poolmath, that would require 90oz. Or is this quart the 67oz from your log? That would be equivalent to 3ppm. That's probably close enough to the 4ppm with the uncertainty in measuring the bleach, knowing the exact pool volume and drop test accuracy.

But yes: My assumption was that during the day you added 45+45+67 = 157oz of bleach to basically keep your FC constant. 157oz of 12.5% bleach is according to PoolMath equivalent to 7ppm for your 22000 gal pool, i.e. without adding any bleach you would have lost 7ppm. If you now kept losing 7ppm per day for the next 3 days when you are away (21ppm in total), but added 5ppm per day (15ppm over 3 days), then you'd go down by 21-15=6ppm. That would get you from 19ppm to 13ppm when you get back. That's what you want now, go slowly from SLAM to target-FC without undershooting.

That's a bit simplified, because once your FC is lower, your absolute daytime loss should get lower (UV makes you lose a certain percentage of your FC, so the absolute loss is higher at higher FC). But you want to be conservative. The last thing you want is to go under your minimum FC. I wouldn't even get close to it. Start slowly reducing the amount of bleach you add per day and see how your pool reacts and try to reach your target range from the top, and learn how much bleach you have to add to always remain a safety margin towards the minimum FC at all times of the day. Best to remain in the target range whenever possible, so you have a safety buffer towards min-FC for days when you can't add bleach for whatever reason (work, kids sick, no bleach available, ...)

I guess the easiest while away would be to just get your dad add 1 gallon per day, that's equivalent to 5.7ppm of FC. That leaves room for measuring errors, and should make sure that you stay above the target range for now. Once you're back, you start the fine tuning and understanding your pool's daily chlorine demands under normal conditions.
 

Ilovemylife1129

Well-known member
Aug 7, 2018
63
Canonsburg/PA
Thank you so much! That explanation was very good and helpful! You even answered my next questions which was how to know how much to put in for my target. So I slowly lower down to the higher end of my target range and then trial to see what my pool needs me to add to keep it at the higher end of my ideal range. Once at my ideal range, will I need to add every day or can I do every other to every 3 days? And I know I should use e little chlorine and pH test every day as much as feasible, and I should test everything once a week correct? And adjust once a week as needed.

mad to that queasy I added two nights ago, it was about a quart which is 32oz. That’s why I was unsure too. Maybe the quart I added an hour before wasn’t showing up yet or I counted off. All of which are possibilities. Human error?!?! Either way I passed lol!
 

mgtfp

Bronze Supporter
Mar 5, 2020
409
Melbourne, Australia
Well done, your patience has paid off:whoot:
From now on, it's all about understanding your pool. Test daily for a while to learn about the chlorine needs of your pool under different sunshine and temperature conditions, and how fast your pH rises and how much acid to add. Stick to the higher end of the target range, that gives you more room for things going wrong.

Also important to understand what impact deviations from the normal routine have, like a big pool party creating higher chlorine demand (sweat and esp. pee consume a lot of chlorine), or a big dump of leaves or dirt after a storm.

Once you got all of this, you'll know how much chlorine to put in each day, and how often you have to test to verify that you're still on target. You'll also learn to estimate how much chlorine you'll lose over a weekend away, and if it's enough to just bring it up to SLAM level before you go, or if you need someone to poor in some chlorine for you.

And look at the min FC in the CYA/FC chart as a red line that you never want to cross, it's not a level to dial in as a target. Chose your target so that considering all the losses by UV and normal bather load you'll always maintain a safety buffer to the min FC. If you expect higher losses (e.g. kids having friends over) then add a bit more chlorine.

The ultimate comfort comes with a Salt Water Chlorine Generator. Once you have that dialled in, you can easily go on holidays without having to worry about your pool. You can go weeks with just testing every couple of days, adding some acid as required. It's an upfront investment, but you'll save on chlorine over the years. Certainly worth saving some money for. I haven't heard of anyone who regretted going SWG.
 

Ilovemylife1129

Well-known member
Aug 7, 2018
63
Canonsburg/PA
Thank you so much!
Here are my results from today. My Dad was adding a gallon of the 12.5 bleach a day while we were gone and I didn’t get test yesterday. Just yesterday was the only day no bleach was added and my FC really dropped from that one day. Also our water went down a few inches while we were gone so we got in and found a hole, well looks like a little slit. Any recommendations on the best under water patch? Could this have been part of our problem?
My TA may have been 77. The water turned blue but with on more drip it was very blue which made 88?!?!
Do I need to adjust my TA if it’s 77/88?
Do I need to lower my pH is it’s 7.5?
The pool math app is suggesting it but I thought they were ok here?
I added a little over half gallon of chlorine and will be testing everyday. I want to aim for 7 since we are losing so much in one day? Hoping when we patch the hole that makes a difference. And it has been upper 80s/low 90s here for the past week.
 

mgtfp

Bronze Supporter
Mar 5, 2020
409
Melbourne, Australia
If FC didn't drop below 3, you might have been lucky, but it was close. That was a higher loss than I would have expected without additional organics in the water (or your dad was hosting one of those massive spring break like pool parties while you where away ;) ).

I'd suggest to bring it up to 7 or slightly above and run another OCLT, just to be sure.

Regarding the TA test: The test is finished once the colour doesn't change any further. When you think you're done, add another drop. When that drop doesn't change the colour, then don't count that drop. So, take the higher reading. I'm a bit confused that one drop is 11ppm. Isn't a drop either 10ppm or 25ppm, depending on sample size being 25ml or 10ml?

I wouldn't force it further down, it will come down on it's own each time you add acid to bring pH down (unless you have high TA in your fill water and are topping up a lot).

pH 7.5 is fine, no need to lower until you reach 7.8 (unless you have high CH and TA).

Not sure what to do about the slit in the liner. Let's wait for someone else to chime in, and have search through the forum, I'm sure there's advice somewhere.
 
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