Pool opening for the season

[Johnny B]

I had enough CYA on hand (& before &I read your post), to Target CYA 30. Tested 1 week later & CYA is 30. Still want me to get to 40?
Good lesson for me. It was indeed taking too much bleach but I didn’t recognize it, 1st year with a sand filter/ backwashing.
Filter pressure hasn’t budged in probably 1 month & I suspect it won’t for practically the rest of the season.
Still want me to get to 40?

What happened to the swimming lady avatar? Women always change things, hairstyle, shoes, etc

Thanks

 

[JasonLion]

CYA at 30 is just fine for now, but in a month or two it will have drifted down. It is usually simpler to raise CYA up to 40 or 50 now, so that it will still be at least 30 at the end of the swimming season.

 

[Johnny B]

My pool sure is going through the acid this year. Every 3-4 days must go from 7.8 to 7.5. Last year was plenty too but less so. Also going through baking soda, TA drops about 10 per week- last year I almost never adjusted TA, beginning of season but then so infrequent I don’t even recall it.
CYA is fine. CC remains 0- no shocking required. CH 250 same as upon spring opening. Borates 30 (last year was 50 & I’m not going to continue with the borates but I must measure it for pH etc). Rust issue & a calcium scaling issue going on- pretty sure those are un-related. This summer is hot, last summer was unusually cooler.
Just want to be sure I’m not missing something. Thanks

 

[JasonLion]

What is your TA level? If the PH is rising that quickly, you probably want to let the TA level come down further than you have so far. Letting TA come down to 60 is normally fine, and you can go lower than that if you have added borates to the water.

 

[Johnny B]

5/29/10 TA 70
6/14 TA 60
6/18 Borates 30
6/21/10 TA 70
7/10/10 TA 50, so Target 70 - 80
7/24/10 TA 80
8/1 TA 70

I thought I was supposed to keep the TA 70 -90, it kept getting < 70 so I finally targeted 80. I’m trying to keep everything in the recommended range since I have that calcium scaling issue ( some anxiety I guess- don't want it to worsen) but I’m still learning from your posts etc.

With my borates at 30, you want a TA of 50 or 60?
Just let the TA fall by itself I assume- don’t treat to lower it, right?

Thanks for all your help.

 

[Johnny B]

TA is 50 & I know that is ok w my borates of 30-40( just re-tested the borates).

How low is too low a TA?

The frequency of acid has declined as you said, now about every 5-6 days. All else doing great thanks to you guys on TFP, chemistry is great but the calcium scaling is ugly but I'm delaying it since we can live w the esthetics

How low is too low a TA?


Thanks

 

[chem geek]

50 is not too low, especially when you have borates in the water. You do want to keep an eye on the saturation index since for a plaster pool you don't want that to get too negative for an extended period of time (weeks; months).

 

[Johnny B]

1- How low is too low a TA?

My chemistry is fine. My Cal scaling was most likely due to a prolonged high pH over the winter in spite of ideal closing. In the future winters I will monitor the pH & keep it in line with acid .
My CH on 8/1/10 was 250 & that was no change from the spring.
I’m going to delay dealing with the Cal scaling since I already tried the low pH + brush + pumice stone; so that leaves me with an acid wash as the only decent option which will reduce my plaster life a few years & I’m just “ a few years” from re-plaster anyways, so I figure I’ll take care of it all at once at the upcoming re-plaster a few years from now.
2- You guys don’t see a problem with that do you?
The Ca scaling has gotten no worse & as I say, future winters will include keeping the pH in range.

I did a search on “saturation index”. I see it on the Pool Calculator; plugging in my numbers (no salt #) I get a CSI of Now 0.24 and a Target of -0.48
3-- What’s the deal with Target -0.48? Am I supposed to do something to reach that? I am confused re CSI.

4- A question re my winter pH monitoring. I assume I’ll be adding acid occasionally (very diluted as Jason said in my other thread here raised-stains-stained-bumps-t21024-20.html
), but my water level is lowered for winter, about how many gallons is 1 inch of water in my pool? I get 412 gal per inch but I better ask.
5- ChemGeek, if you’re still following me here, do you like my plan on that link above or do have any comments on my last post in that thread. And should I expect to be adding acid as frequently in the winter as I do now (every 5-6 days?)
Thanks for the suggestion to watch my CSI.

Thanks

 

[chem geek]

When using The Pool Calculator you enter in your current numbers into "Now" and the numbers you want to achieve into "Target". When just calculating the saturation index, you can just enter numbers into one column, such as "Now", and then just read off the index in that column. The saturation index in the "Target" column would be bogus since the numbers there are just whatever was there the last time you went into the calculator. So it sounds like you have a CSI of 0.24. This means that you could lower your TA, pH and/or CH levels to reduce the chance of scaling.

18'x34'x(1/12)' is 381.5 gallons.

Your plan for a sump pump to circulate when doing acid addition over the winter sounds good to me. I do not think you will need to add acid as often as you do now since the water temps will be cold so whatever is causing your pH to rise so fast now will likely slow down with colder temps. Just test after a week the first time to see how things go and then extend the time which I suspect you'll be able to move to once a month.

 

[Johnny B]

Where do I learn about CSI, my searches haven’t been that fruitful?

I told you the wrong CSI in my prior post, sorry.
My chemistry #’s were accurate but the gallons went to a default I suppose, when I put in the correct gallons I get a CSI of -0.48 & it says “Potential to become corrosive to plaster” which is my issue with the Cal scaling ; yet it also reads “Less than -0.6 is suggestive of problems for plaster, …. Greater than 0.6 is suggestive of problems for all pools”. So I am in range but getting to close to -0.6 I assume? So I should alter something, right? TA or pH or a bit of both? My guess is that you’ll advise I try to maintain a certain pH & TA slightly different than what I have been. What I have been doing is:
pH- it creeps to 7.8 in 5-6 days & I lower it to 7.5
TA- I learned in this thread to let it drop below what I was maintaining of TA 70

My current #’s
FC 3-7 range, lets say FC 4
CC 0
CYA 30
pH 7.5, It creeps to 7.8 in 5-6 days & I lower it to 7.5
TA 50
CH 250
Borates 30-40, I do not want to add more borates now or in the future

Can you please make a suggestion how I can alter something to move away from this ““Potential to become corrosive to plaster” issue if indeed that is a concern?
Thanks

 

[chem geek]

The CSI does not change based on the number of gallons so I'm not sure what you are doing in The Pool Calculator. When I enter in numbers of FC 4, pH 7.5, TA 50, CH 250, CYA 30, Salt 0, Borate 35, Temp 80ºF I get -0.39 for the CSI. At higher temps, the CSI would be higher (at 88ºF it would be -0.33).

I don't know why your pH is rising so quickly given your low TA and also having Borates in the water. Do you have extensive water aeration such as waterfalls, fountains, spillovers, etc.? I didn't see anything in your signature that would indicate this. If your plaster was new then the curing of plaster can make the pH rise quickly, but your pool was built in 1992.

CSI is the Calcite Saturation Index and is very similar to the Langelier Saturation Index (LSI), both of which are measurements of the degree of saturation of calcium carbonate where 0 is saturated, > 0 is over-saturated, < 0 is under-saturated. One intentionally saturates pool water with calcium carbonate in order to protect plaster surfaces -- too little calcium carbonate and such surfaces can dissolve creating pitting and thinning the plaster; too much calcium carbonate and one can get scaling. So in your case to avoid scaling you want the CSI to not get much above 0 so you should be fine where you are, especially since the pH tends to rise.

 

[Johnny B]

Thanks, as always, very helpful & I’m relieved that I’m in a decent CSI range not in need of altering something.
I get the same CSI when I input your #’s, I was a bit different on the temperature & borates


I don't know why your pH is rising so quickly given your low TA and also having Borates in the water.
Me either, but its doing better as the TA falls
Do you have extensive water aeration such as waterfalls, fountains, spillovers, etc.?
No.
but your pool was built in 1992.
Re-plastered in 2006, so still this is not “new” plaster.

So in your scaling case, to avoid further scaling, you want the CSI to not get much above 0 so you should be fine where you are at -0.39, especially since your pH tends to rise.

I guess one concept of the CSI I am still unsure about is the fact that a “recommended range” of CSI isn’t mentioned, like we see a range for pH, a range for FC, etc. I do read: "Less than -0.6 is suggestive of problems for plaster, tile, stone, and pebble pools. Greater than 0.6 is suggestive of problems for all pools.”
Is my thinking correct that a nice goal is a CSI of 0, yet we don’t take much action to move toward 0 so long as we aren’t too close to either -0.6 or 0.6? So the “acceptable range” is from -0.6 to 0.6? But that can’t be true in my present Cal scaling situation, because as you say, I don’t want my CSI to get much above 0; so if I acted as if all is swell with my CSI so long as it doesn’t get too close to either -0.6 or 0.6, I would be asking for problems; instead as you say, I don’t want to get much over 0.
Don’t mean to over-think or over-analyze this CSI issue, but obviously it is relevant here. Had I been on the ball with CSI & monitoring pH last winter, it’s likely I wouldn’t have a Cal scaling ugly plaster issue now; I did not know I had to watch all this over the winter, we never did a thing in the prior 17 winters.

All my times using the pool calculator, I have never considered CSI but I suppose I should be always looking at that.

I look forward to your reply, & I may be asking for help when I see my CSI get to 0 because I don’t want it to get much over 0 or my scaling could worsen.

Thanks

 

[chem geek]

The usual advice in the industry is to have the saturation index be between -0.3 and +0.3 which are technically values where the calcium carbonate concentration is half-saturated and double-saturated, respectively. The Pool Calculator is being more liberal in its warning levels because this process is slow so one should not panic about it.

I wouldn't worry about your CSI getting somewhat above 0. The reason you had scaling in your pool was that the CSI went VERY high, mostly because your pH went very high. Based on info in this post of yours using a pH of 8.2, CYA 30, Borates 30, TA 90, CH 250 and assuming a temp of 70ºF, the CSI in The Pool Calculator is +0.45 though if the temperature or pH were actually higher, then the CSI would be even higher. Usually, actual scaling isn't seen until the CSI gets to +0.7 or +1.0, but technically anything above zero can theoretically scale.

So for you, targeting say -0.3 for the CSI when your pH is at 7.5 is reasonable since it will be at 0.0 when the pH rises to 7.8. This isn't a big deal.

 

[Johnny B]

Thanks. A big help as usual.
I failed to mention how little chlorine my pool has been using, far less than last year ( after the ammonia issue I mean, & actually about the 1st half of this season), huge difference.
My TA remains 50. Assuming my #’s don’t change much, how low a TA is too low? 40? 30? Or keep it at 50 if it drops?

My current #’s
FC 3-7 range, lets say FC 4
CC 0
CYA 30
pH 7.5, It creeps to 7.8 in 5-6 days & I lower it to 7.5
TA 50
CH 250
Borates 30-40, I do not want to add more borates now or in the future

Thanks

 

[chem geek]

Unless you see a big difference in the rate of pH rise and/or the amount of acid you are using per week at 40 ppm vs. 50 ppm, I wouldn't have the TA lower than 50 ppm. At least you have Borates in the pool for some additional pH buffering. You might also see if the pH tends to rise from 7.5 more quickly but then slow down as it gets to 7.8. If that is the case, then you might try targeting 7.6 or 7.7 as a target pH when you add acid.

You might have some other sources of rising pH in which case lowering the TA further may not help. As I wrote, if you don't notice a benefit at 40, then leave it at 50. After you've decided where to leave the TA, then adjust the CH to get your saturation index up somewhat.

 

[Johnny B]

...
So for you, targeting say -0.3 for the CSI when your pH is at 7.5 is reasonable since it will be at 0.0 when the pH rises to 7.8. ....

10/2/10 test results
pH 7.5
FC 4
CC 0
TA 50
Borates 30
Temperature 72F
CH 275-300, lets say 285
CYA on 7/10/10 (almost 3 months ago) was 30 so I added with a Target of 40. FC has been behaving wonderfully; my guess is that CYA is 40. Want me to test it just ask.
CSI -0.45


If I put in a CH of 350 (the maximum in the “recommended level” range), My CSI moves to
-0.38. Would you like me to move the CH from 285 to 350?
If yes, I have some old (2 + years) “Leslies Harness Plus” which states: “Adding 1-1/4 pounds of Hardness Plus to 10,000 gallons of water will raise the Calcium Hardness by 10 ppm.”
From CH 285 to CH 350 is 65ppm

My pool is 19,800 gal; so 2.475 pounds will raise it 10ppm x 6.5= 16.09 pounds
But the pool calculator says to use 191oz or (11.94lbs)

Here is Leslies Harness Plus which states it is Calcium chloride :
http://www.lesliesmsds.com/Document/21/ ... 0f1c83.pdf

1- Would you like me to move the CH from 285 to 350?
2- If yes, is it 16.09 pounds or 191oz (11.94lbs)?
3- It says to broadcast it. Or do you like it in a sock above the returns?


Thanks

 

[chem geek]

It's not a big deal. If you think your pH is going to generally be above 7.5, then you can leave things as is. Up to you.

The instructions seem to imply that the product is Calcium Chloride Dihydrate which is why it says to add more (252 ounces weight), but the MSDS implies that it is Calcium Chloride Anhydrate which would be less (191 ounces weight). I can't tell you which one is right, but you could always add the smaller amount and re-measure.

For distribution of the calcium chloride you can either broadcast it or add it slowly over a return flow, but will likely need to brush the bottom as well since it doesn't dissolve completely very quickly. You don't put it in a sock like you would with CYA -- if you were to do that it could get quite hot as the dissolving of calcium chloride is exothermic (i.e. produces heat).

 

[Johnny B]

Oh I see the “more drastic” effect that pH has on CSI. By fiddling with pH in the pool calc, using the same test results, simply letting the pH get to 7.7 gets me in the “more preferred CSI range of -0.3 – 0.3”; it results in a CSI of 0.29. Even having the pH get as high as pH 8.7 (not something I want, just fiddling with the #’s to learn about CSI) keeps things well in the “more preferred CSI range of -0.3 – 0.3”.

I’m all for leaving things as they are so that is what I will do ( NOT raise my CH). But still a few questions.
1- For now, while pool remains open. I should target a pH of 7.6 (rather than 7.5 as I have been) to help stay closer to a better CSI range?
2- The “recommended pH range” in my situation is 7.5-7.8. This remains the case now, while pool remains open I assume?. (FYI, temperatures will be quickly moving toward 60F for a closing in probably less than a month.)
3- Is my “winter/closed “recommended pH range” also 7.5-7.8? Reasons I ask is
a- I see the effect temperature has on CSI , and
b- All my discussion here is to try to keep my pool as trouble-free as possible, specifically, hoping to keep this Calcium scaling issue from getting worse (trying to milk a few more years before I’m forced to re-plaster). Stated differently, in the winter, is it ok to let the pH get to 8.2 then Target it back down to 7.6? Or is a winter pH of 8.2 ill-advised in my case? and
c- Pretty sure my cal scaling issue was letting my pH get to high for too long last winter ( as I say, I’ll be monitoring things all winter).

I anticipate that I’ll be posting test results here this winter being sure things are ok; perhaps then it’ll require raising CH etc.

Hope I’m not over-analyzing here, but neglecting such things is likely why I ended up with my scaling issue. I didn’t know I had to deal with this all winter.

Edit: I fiddled with the CYA too to see how it affects CSI, I’ll definitely get that CYA test done at closing time, and as I said I’ll do it now if you ask but I think I’m fine guessing that the CYA is 40 or less.

 

[chem geek]

As the temperature drops, the pH will naturally rise even if there were no carbon dioxide outgassing, so the CSI stays fairly constant. You could certainly let the pH rise to 7.8 as the temperatures dropped, but I wouldn't go above 8.0 because 1) it's hard to accurately measure higher pH than that with your test kit and 2) high pH can lead to metal staining if you've got any metals in your water. To prevent scaling over the winter, I'd make sure your pH doesn't get above 8.0 (when the water cools down) and if you wanted to target 7.8 and check on it periodically, that would be fine.

 

[Johnny B]

My assumption that my CYA was 40 was wrong, it remains CYA 50. Do you want me to alter anything to get a better CSI & minimize my Calcium scaling issue?

I am ready to close. I shocked 2 days ago (Target 16, reached & held overnight) & am awaiting the FC to fall to about FC 12

Here are my test result
pH 7.6 (my new Target is 7.6)
FC lowering towards 12, or may be there now
CC 0
TA 50
CH 285 (16 days ago)
CYA 50
Salt 0
CYA 50
Borates 30
Temperature 60
CSI -0.51 (Potential to become corrosive to plaster)
(if I let the pH get to 7.8 the CSI is -0.36)

I will leave things as they are & just keep the winter pH between pH 7.8-8.0 as you said above. Just want to be sure you don’t want me to alter CH before I close for the winter.

Thanks