Pool math says" Potential to become corrosive to plaster" with rec levels

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mikemass

mikemass

0
Jul 10, 2013
490
Northern Howell, NJ
So I am playing with the pool calculator. I currently have 2 windows open side by side on my computer:

Window 1: Pool School - Water Balance for SWGs

Window 2: http://www.troublefreepool.com/calc.html (with my numbers)

I took all recommended numbers from Water balance for SWGs and plugged in the dead midpoint of the range into the right hand column of Pool Math ("target" column).

In the left hand column (the "Now" column), I plugged in my current numbers, which are pretty good and also within range.

When I mouse over the CSI in the "Now" column apparently my pool is: Corrosion of plaster likely despite having decent numbers. (not perfect, but decent enough)

But if I mouse over the CSI in the "Target" column the pool is still: Potential to become corrosive to plaster

my CH is a tad low and I plan on bringing that up this weekend, which will help. Also I would love to do the borates again and get those to 50 (had it 2 years ago and loved it, but skipped it last year, so my concentration is down) But the higher the borate # I plug in, the more corrosive the CSI gets.

I am well aware that the pH is the largest factor in the CSI calculation. But even though mine is currently on the low side, corrosion is still "LIKELY" with all values being dead center of suggested ranges.

Pool%20Math.jpg
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Mike, I've been racking my brain on this one as well and see everything you do. Then I think it "clicked". Remember this tool is designed to show us potential problems on any given day. The one thing that is always an unknown variable around the country (or world for that matter) is temperature. The colder the water temp the more drastic CSI is affected. Generally we don't worry too much about it in cold water because pH has a tendency to rise in colder water, thereby offsetting CSI a bit as well. So I think you'll find if you change your water temp to what you show today (mine is almost 90 for example), you'll see a huge swing in the CSI. Here are a couple more discussion about that very subject that I hope help you:

CSI and cold water..
CSI and cold water?
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Thanks Tex. I know not a huge deal and may seem like I am splitting hairs. But I would just expect that if you plugged all variables in at the low end of range, or all variables in at high end of range, your CSI should be balanced. Certainly mid point at "swim-able" temps. But yes. If I raise the temp to 85 degrees the "target" gets balanced. The "Now" still has a ways to go. pH is the largest factor I see as i play with the numbers. Would love to see this algebraic formula.
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

I have a spreadsheet in my sig that mirrors pool calc with the same formulas.

Also, it says there is a "Potential" and not likely. The more negative the CSI the more likely but time is a big factor.
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Both the CSI are within the acceptable range. I fail to see the problem, other than the caution statement which just makes you aware.
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Mas985 - Awesome! Thanks for the reference to the spreadsheet in your sig. I like that I can see the formula on those. Much appreciated.

To clarify the verbiage I used earlier quoting the caution statements on the Pool Math page. Potential was used plugging in all suggested levels. Likely was used on my numbers (not shown in my OP).

Either way, it is not unheard of for guys to spend 25, 50, 100 thousand dollars and up to build their backyard oasis. The cost of a replaster and tile job alone would be north of 10 G's. So any mention of corrosion of plaster, be it likely or just a mere potential is concerning.

The only word that makes me feel warm and fuzzy is Balanced when I mouse over that field. That's what i am shooting for.
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Well, I added some calcium this weekend. Brought it up to 375. Every variable now is right in the recommended range and I still have a CSI that is Potential to become corrosive to plaster. I would like to add Borates, but if I do, my CSI will turn even more negative.
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

So raise the pH if you are concerned ... not sure why you are trying to make this so difficult ;)
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

I didn't think I was being difficult. Just trying to decide what is more important.

1. Follow the recommended chemistry levels set forth within this web site, and have a CSI at or below -0.31
2. Shoot for a balance that gives me a CSI greater than -0.31 and hence "balanced"

I would have hope both were the same so I wouldn't have to make the decision.
 

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Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Can you please post your current results below, and the date these were last tested on.

pH:
TA:
Cya:
CH:
Salt:
Borates:
Water Temp:
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

Leebo said:
Can you please post your current results below, and the date these were last tested on.
Click to expand...

Sure
6/5/2016 6:00 pm (right as pump was shutting off for the day)

pH: 7.5
TA: 80
Cya: 80
CH: 375
Salt: 3600
Borates: 10* see below
Water Temp: 78

comes out to a CSI of -0.33

* This is an estimate as I had it at 50 during the summer on 2014 and have not added since. That means there has been multiple reductions in the way of splash out, dropping level for winterization (x2), rain water, and another water level drop earlier this year when I overshot my salt.
 
Improvement after rain

Leebo, I took another round of tests tonight:

Date: 6/6/2016
Time 7:30pm
Day's conditions: Mostly sunny, 85 degrees
Special notes since last night reading: Heavy rain added about 1-1/2" of water to pool last night

FC: 5.0
TC: 5.0
CC: 0.0
pH: 7.5
TA: 80
CYA: 70-75 (but not 80 - I really took my time and tried hard to get an accurate read)
CH: 370
Salt: 3600
Borates: 15 (using LaMotte Insta Test Strips)
Water Temp: 81 deg F

CSI as per The Pool Calculator: -0.29 - BALANCED! By one-hundredth.

So, as the water temp increases I know I will continue to be 'more' balanced (further to the right on the number line), everything else being equal.

Also, I think I will add another 10-11 lbs of Calcium to get that closer to 400 as it is my understanding that running a CH on the high end is preferred for plaster pools. It is also the one factor I can adjust to get CSI closer to 0.0 so I can counteract the planned addition of Borates which will pull the CSI back to the left side of the number line.

Do you agree with my plan?
 
Re: Pool math says" Potential to become corrosive to plaster" with rec levels

As you can now tell it is impossible for us to create a table that covers EVERY pool woth "firm" numbers. There are multiple factors that come into play with every user. Because of this we give members the knowledge to maintain their pool, not a firm set of numbers to stay between.

In your case either adding CH or slightly increasing your pH will help you with your CSI. keep in mind also, as water temps go down and cause PoolMath to warn you of problems you need to remember that the lower temps slow down EVERYTHING. Any deterioration of plaster is also slowed down as explained below,
CSI and cold water..
 
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