Cloudy water, rising CH and TA

judas

Member
May 25, 2007
16
MA
I need a little advice on the order of things to address this issue.
My CH has been a bit high since June (the amount of calcium chloride I added beginning of the season was apparently way too much, my initial reading was 150).

Water has been crystal clear and chlorine numbers were good up until a couple days ago; it's now cloudy, but not too bad...I can still see to the bottom of the pool. No visible algae.
Cleaned out the DE filter grids yesterday. I performed a test today and these are my numbers:
FC 0.5
TA 110
CYA 30
pH 7.5
CH 725

Previous test results from June:
TA 80
CYA 35
pH 7.5
CH 675

Per poolmath, to lower CH I'll need to drop my water volume (gotta test the house water CH to find the exact volume to replace); to drop TA I need reduce pH to 7.0-7.2 and then aerate to increase pH.

Should I address the CH first, then worry about the TA?
Anything else I should be doing?
 

Dtkokay

Well-known member
Dec 31, 2019
305
Houston, Texas
You should aim to lower your CH in the long term by draining and refilling water. However, of much more immediate concern is that you basically have no chlorine In your water. That’s why your water is cloudy. Get some liquid chlorine in there asap, and you should do an overnight chlorine loss test to check whether you have algae growing. Just because you can’t see it doesn’t mean it isn’t there.
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
I just had a look through your PoolMath logs. Looks like your CH was 100-150 just before you added 50 pounds of calcium chloride, and after that your CH was 675 and kept rising to 725. That doesn't really fit together, those 50 pounds should have raised your CH by 270.

Did you top up a lot of water lately, and do you know the CH of your fill water?

How did you test your CH?
 

judas

Member
May 25, 2007
16
MA
The CH thing has been boggling me since it happened. Not sure if my pool volume estimate off or what. I only topped off once this season; but I plan on testing the hose water CH this morning. We've had a couple heavy downpours (no steady rain this summer though). I use a fresh TFP test kit for everything.

And lo and behold there is now visible algae in a couple places.
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
That CH is very odd. Your pool volume needed to be half as big as assumed to explain this massive overshoot in CH. And if that were true, than the 7.5 lbs of stabilizer you added would have increased your CYA by about 90, so I'd rule that out. Not that CYA is a good way to estimate your pool volume, but a factor of two should be visible.

While we keep thinking about that, you should start attacking that algae asap - it's time to SLAM!

Don't worry about lowering that TA for now. But it is interesting that it got up from 80 to 120 without adding baking soda. This, together with the CH jump, could be explained by topping up a lot of evaporated water with fill water that is high in CH and TA. But if you say that you didn't top up much, then that explanation doesn't seem to fly...
 

judas

Member
May 25, 2007
16
MA
Maybe the rain has contributed to the TA and CH increase? We've had a few heavy downpours this summer when I've had to lower the water. But I've only added once (and just a small top off) from the hose this season.
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
The only other explanation on your CH mystery I could come up with so far is, that you added 50kg of calcium chloride instead of 50 lbs. Any chance that might happened?
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
Maybe the rain has contributed to the TA and CH increase? We've had a few heavy downpours this summer when I've had to lower the water
Rain water has 0 CH and TA. So rain reduces those parameters by dilution. If it gets to the level where you have to drain, you will remove some CH and TA, so the levels are effectively reduced (that happens in my pool over winter - a lot). If you don't drain and the added rain water just evaporates over time, you're back where you started.
 

judas

Member
May 25, 2007
16
MA
The only other explanation on your CH mystery I could come up with so far is, that you added 50kg of calcium chloride instead of 50 lbs. Any chance that might happened?
Definitely was in pounds. Per poolmath app, I was supposed to add 67 lbs to bring my initial CH from 150 to the target of 450.
There is probably a good chance I screwed up measuring, and I really added way over the 50 lbs I thought. That's gotta be the only explanation.

On a side note, I just plugged in the numbers using the online poolmath vs the app, and there seems to be a discrepancy - using the online calculator, it says I should've added 888 oz by weight (55.5 lbs).
The app says I should've added 1067 oz (67 lbs).
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
You must have picked imperial gallons instead of gallons in the App. 55 lbs is about right to raise CH by 300, so in the old Web-PoolMath you must have picked the right "gallons".

That at least explains why you wanted to add 50 lbs in the first place, that would have increased your CH by 225, from 150 to about 375, which is a reasonable level (I'm glad you didn't add the amount to get to 450, there is actually no need to aim for the middle of the ideal range. It is a range for a reason - people with high CH fill water will be happy if they can keep it as low as 650, and those with low CH fill water and/or a lot of rain can struggle to keep it as high as 350). But because your pool actually has 20000 gal and not 20000 imp gal, it actually should have increased your CH by 270 to about 420. But in your case, CH was increased by 525 (initially to 725, and then it kept rising even to 725). There is something else going on.

How did you add the calcium chloride to your water? It creates a lot of heat when dissolving in water, and shouldn't be dumped into one spot in the pool and let sit there, especially such a large amount, it should be distributed over the surface and stirred in with the brush. When adding large amounts of any chemical, it is better anyway to add it in smaller batches and test before adding more to make sure that you are not overshooting too much.

I have heard of vinyl liners getting damaged by the heat created by dissolving calcium chloride, not sure if a plaster pool could get damaged by the heat being created if a 50 lbs pile of calcium chloride dissolved in one spot, and then some calcium from the plaster got released. That is just me thinking, I haven't actually heard of that happening. But something must have happened to explain this massive overshoot (even when considering the gallons mix-up). I don't think that you would have got the measurement that wrong - to get to 675 you must have added about 88 lbs (or even 106 lbs when considering the latest 725 measurement as the correct test result).

How old is your plaster?

And have a look at the CSI to help you choose the right CH level. For a plaster pool it should be between -0.3 and +0.3 (I have a SWG and even keep it between -0.3 and 0 to avoid scaling in the cell). You can turn on "track CSI" and "track temperature" in the App, then it will calculate CSI for you:

 

judas

Member
May 25, 2007
16
MA
DAMMIT!
You were right I had imperial gallons set on the app. Just fixed that.

When I added the calcium chloride, I added it to pool water in a 5 gallon bucket, mixed, and emptied it in the pool slowly and while walking around it. Took a while :)

Pool plaster is really old...can't say for sure, but I know the pool was built in the late 70's early 80s, and knowing the previous owner (we are the 3rd), it may have been only plastered once. It is definitely due. It's on the list, it's just a huge expense we haven't been able to budget for, but I think it's time.

Numbers as of this morning:
FC 3.5
TA 110
CYA 30
pH 7.2
CH 725

pH has dropped a little, but the water is back to being crystal clear. Overnight FC lost test = 0.5
Tracking CSI now....looks OK.
Thanks for your help - I think we're getting somewhere!
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
Looks like you are in a similar boat to me, my pool is also from the early 80s, never been replastered, so it's looking a bit tired. One day...

Glad we sorted one of the problems out. Still don't understand the big jump. Just keep an eye on the CSI and see if there are any more CH jumps. I guess you'll get some rain over fall/winter in MA, that might be enough to bring CH down over time. If it was 100-150 before, then you don't seem to have a calcium accumulation problem.

Are you doing any renovations, could plaster or concrete dust got into the pool?

TA should come down on it's own each time you add acid to bring pH down. With the high CH you'll want the pH on the lower 7 half to control the CSI.

How high did you take FC in your SLAM, can't really see that in the PoolMath logs?
 

judas

Member
May 25, 2007
16
MA
re: renovations...I replaced some waterline tiles back towards the end of May/beginning of June; I did lose some thinset/grout/cement mix to the pool, but that was all vacuumed out and the the CH wasn't tested until the repair was completed. Could there still be some dust that isn't getting caught by the pool robot?

For the SLAM, FC was taken up to 12ppm based on the chart in pool school.
 

mgtfp

Bronze Supporter
Mar 5, 2020
397
Melbourne, Australia
It would look like a very late reaction. And it was very sudden - you tested before you added calcium chloride and a few days after, and the increase came within these few days. But it seems to be the best explanation, having ruled out everything else.

If you passed all SLAM criteria, then try to keep the FC at the upper end of the target range, always keep a buffer to the min FC. And keep a good look if any algae returns, and check hidden spots.
 

judas

Member
May 25, 2007
16
MA
It would look like a very late reaction. And it was very sudden - you tested before you added calcium chloride and a few days after, and the increase came within these few days. But it seems to be the best explanation, having ruled out everything else.

If you passed all SLAM criteria, then try to keep the FC at the upper end of the target range, always keep a buffer to the min FC. And keep a good look if any algae returns, and check hidden spots.
That's really the only explanation - one that I didn't even consider. Should be taken care of after I winterize the pool this season.
I've been inspecting and brushing every day; for some reason this time of season has always been the time for algae become a problem for me.
I appreciate all your continued help!
 
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