Test Results and Pool Calculator Question/Issue

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johnsimion

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Aug 12, 2014
49
Las Vegas, Nevada
Hello, I drained 3/4 of my pool, blasted off the scale, and refilled it towards the end of August. Using two softeners, I refilled it mostly with soft water and there's a soft water feed line attached, so this is not the typical Vegas hard water. My CH is typically in the low 240s. I then installed a SWG and finished adding salt by August 28. I test my water either daily or every couple of days, and since things settled down, I have a crystal clear pool and the water feels great -- no itching, burning, or anything. I get consistent readings, but some of them aren't what the Pool Calculator wants me to have and the goals set by the Pool Calculator are just WEIRD. These are today's readings:

FCL: 4.98 (a bit high because of being out of town for a couple of days -- usually around 3.5 or 3.8)
PH: 7.6
ALK: 91
CH: 255 (usually around 240)
CYA: 43
CSI: -0.2 (balanced)
Salt: I just entered 3400 ppm into the Pool Calculator because I do not have test results for salt. See below.

Here are the questions/issues:

1) The pool calculator says my ALK should be 60-80. I have never gotten it that low since refilling the pool. On Monday morning before leaving town, I tested the water and got a PH of 7.8 and ALK of 93. I'm almost always at 7.8 no matter how much acid the Pool Calculator tells me to use to get down to 7.5. Okay, so I figured I'm going out of town so here is my chance to get the PH way down and reduce the ALK. I used the calculator to tell me how to get the PH down to 6.9 and it told me to use a bit less than 3 quarts of muriatic acid (29%). Instead I actually used almost a full gallon and as you can see, the PH today (Thursday) is already (back at) 7.6 and the ALK is at 91. Thus I reduced the PH a whopping 0.2 and the reduction in ALK is within the margin of error. Two weeks ago my ALK was actually less than my current reading. It seems obvious that the Pool Calculator doesn't ask me to add enough acid, but I have no idea how much more I should be adding in order to reduce the ALK level.

2) The salt test strips I bought from the pool store tell me that there is only about 1100 ppm of salt in the pool. That is ridiculous -- I added 14 bags to my 19,000 gal pool as the bags recommend and the pool tastes pretty salty. The SWG wants 3400 ppm and is happily generating lots of chlorine at only 60-80% capacity. Do I need to get better results? Salt doesn't seem to change the results much on the Pool Calculator.

3) If I used the goal settings in the Pool Calculator (splitting the differences on the ranges), it says my CSI would be -0.34 with the "potential to become corrosive to plaster." Yet the same Pool Calculator shows that my existing values are "balanced" at -0.26 and I have had frequent results around 0.0 which are also shown as balanced. What gives? Why would the Pool Calculator give me GOALS that would result in plaster corrosion??? And of course if I add even more acid in order to get the PH down, the Pool Calculator is going to have a cow about plaster corrosion. I even tried adding the recommended amount of borate into the Pool Calculator goals to see what would happen, and that makes the "potential to become corrosive" worse yet.

4) Even though the Pool Calculator says my pool is balanced, I am still getting some scaling and calcium spots where the spa spills over into the pool. Thus far we have been able to eliminate it by spraying it with white vinegar, but maybe I should work harder to reach the Pool Calculator goals and risk the plaster corrosion in order to keep the &*%&& scale out? Maybe it makes a difference that my pool is Pebble-Tec instead of plaster???

I don't know what to believe any more. Am I overthinking this? I don't know whether I should trust the Pool Calculator or what.
 
I would say you can trust Pool Math (link at top of page).

Instead of strips, I would pick up a K-1766 Taylor Salt Test kit

Are you verifying any of the numbers or just relying on the ColorQ?

When you say you are "getting some scaling and calcium spots where the spa spills over into the pool" is this above or below the water line?
 
I am not sure you realize, but we put little faith in the ColorQ and prefer the drop based testing ... but if you want to trust it we can offer advice.

Also realize that we recommend using PoolMath now.

1) None of that makes sense if you have the pH and TA set in the NOW column of PoolMath correctly. I would suspect testing error (because it is low hanging fruit ;) )

2) As long as the SWG is happy do not worry about it. But, I suggest the drop based salt test over the strips. Realize that the SWG and the even the drop test are only good to +/- 400ppm.

3) That is not what it says. It says you are at risk if the CSI get < -0.6. You are fine and you want it a little negative to lower the likelihood of scale developing in the SWG. The calculator does not care how much acid you use. Only the actual pH of the water matters ... do you trust your results? I don't think I do since pH is one of the easiest things to adjust. You sure you are using 30% and not the 14% muriatic acid?

4) That is not calcium scaling. Those are mineral deposits that result when water evaporates and leaves behind the minerals. No way to stop that.
 
Am I overthinking this? I don't know whether I should trust the Pool Calculator or what.
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Yes, you are overthinking. The Pool Calculator is not intended to manage or fix discrepancies in your pool.

It is intended to calculate the dosages (if any) you need to keep your pool in balance. It also provides some suggested guidelines but it has to be your input that manages the pool.

The knowledge of what that dosage should be comes from your learning and understanding your pool.

You must maintain your own pool from knowledge you have gained from this forum and perhaps other resources. Simply use the pool calculator (that has no brain) to figure your dosages so you don't screw up the math.
 
Are you running the waterfall and/or the spa spillover? Aeration causes pH to climb and that is my guess as to why the pH is rising so fast. If the fill water is high in pH and you are adding a lot, then that could be another source of the rising pH.
 
Tim 5055 said: "Are you verifying any of the numbers or just relying on the ColorQ?" Relying on the ColorQ. I have read the various threads here that diss the ColorQ and the gist seemed (with them) to be inconsistent results. That has not been my experience. I am being very careful to do the tests with the instructions right in front of me, and my own results have been extremely consistent on a daily basis. I see the PH and ALK creep upward slightly but very little change on a daily basis. The FCL, TCL, CH, and CYA are giving me very consistent results that never really change beyond a couple of points up or down. The machine may not be accurate but it is at least consistent in its inaccuracy. Tim 5055 also said, "When you say you are "getting some scaling and calcium spots where the spa spills over into the pool" is this above or below the water line?" Above the water line, near the spillover for the spa. I haven't seen it elsewhere.

I said, "If I used the goal settings in the Pool Calculator (splitting the differences on the ranges), it says my CSI would be -0.34 with the "potential to become corrosive to plaster." Yet the same Pool Calculator shows that my existing values are "balanced" at -0.26 and I have had frequent results around 0.0 which are also shown as balanced." To this, jblizzle said: "That is not what it says. It says you are at risk if the CSI get < -0.6." To this I respond: Yes, it does say you are at risk if the CSI gets less than -0.6; however, it ALSO says "potential to become corrosive to plaster" if I mouse over the CSI field when it shows -0.34 under Results in the "Goal" column. Note that I am using the following from the recommended goals: FC Goal 4-7, I used 4 as my goal; PH goal 7.5 to 7.8, I used 7.7; TA (ALK) 70 to 80, I used 70; CH 250-350, I used 250 because I'm trying to prevent scaling; CYA 70-80, I used 75 as my goal (theoretically) although I really don't understand why I would need that much; and using these as my goals, the PoolMath shows a CSI of -0.34 and it says "potential to become corrosive to plaster." Interestingly, PoolMath and Pool Calculator both say I'm balanced using the figures I reported in my original post. What I don't understand is WHY the suggested goals would give a result that **apparently** is not as good as my actual results seem to be.

jblizzle also said, "Only the actual pH of the water matters ... do you trust your results? I don't think I do since pH is one of the easiest things to adjust. You sure you are using 30% and not the 14% muriatic acid?" The acid is definitely 29%; I just checked the label. As for trusting the results, I do get different results from adding the acid, I just don't get nearly the results that PoolMath or Pool Calculator predicts I would get. In other words, my PH tests 7.8 and the Pool Calculator says I can get my PH down to 6.9 by using 3 quarts of acid; I added more than 3 quarts and two days later the PH tests 7.6. I simply don't think it ever got down to 6.9 because in the past when I'd try to get the PH down to 7.4, the amount of acid the Pool Calculator told me to use was woefully inadequate and I have NEVER been able to get the PH to go down to the level predicted. The PH goes down, it just doesn't go down nearly as far as predicted. Heck, when I was in Florida I used to add a lot more acid than PoolMath is telling me to add now. Heck, 3 quarts is hardly anything in a 19,000 gallon pool -- when I was in Florida my pool was 20% smaller with a SWG and I used add 6 quarts a week! I'm thinking there is something wrong with that calculation. Next time I am going to try doubling the acid it predicts and see if that works.

jblizzle also said in reference to the apparent scaling I had noticed near the spillway of my spa: "That is not calcium scaling. Those are mineral deposits that result when water evaporates and leaves behind the minerals. No way to stop that." I think that is correct. The wind blows a lot here and the spillover tends to splash all over when the wind blows. Also, I have not seen the calcium anywhere else. I had been hoping that using primarily soft water in the pool, and keeping the calcium level low and the PH low would also prevent this, but I guess I was wrong. I can't seem to keep the PH down anyway. At least it cleans up easily with vinegar spray.

Ping said, "Are you running the waterfall and/or the spa spillover? Aeration causes pH to climb and that is my guess as to why the pH is rising so fast. If the fill water is high in pH and you are adding a lot, then that could be another source of the rising pH." The waterfall only runs when specifically turned on, but the spa spillover cycles on and off due to the in-floor popups. I agree that this is causing the PH to rise ... but my experience has been that the PH seems to hit 7.8 and then stay there. Ever since I began testing, I have not seen it go over 7.8. Several times I have tried to reduce it with acid to get it down to 7.4 (or lower to get the ALK down) but it immediately comes right back up to 7.8. I suppose I ought to just leave it alone and see if it will ever go over 7.8?
 
johnsimion said:
Tim 5055 said: "Are you verifying any of the numbers or just relying on the ColorQ?" Relying on the ColorQ. I have read the various threads here that diss the ColorQ and the gist seemed (with them) to be inconsistent results. That has not been my experience. I am being very careful to do the tests with the instructions right in front of me, and my own results have been extremely consistent on a daily basis. I see the PH and ALK creep upward slightly but very little change on a daily basis. The FCL, TCL, CH, and CYA are giving me very consistent results that never really change beyond a couple of points up or down. The machine may not be accurate but it is at least consistent in its inaccuracy. Tim 5055 also said, "When you say you are "getting some scaling and calcium spots where the spa spills over into the pool" is this above or below the water line?" Above the water line, near the spillover for the spa. I haven't seen it elsewhere.
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Well then, I will stick with my comments/questions.

I don't have a ColorQ, haven't played with a ColorQ and didn't enven sleep at a Holiday Inn Express last night, so you understand my basis for comments - basically jsut what i have read. You hit the nail on the head about what I was thinking; "but it is at least consistent in its inaccuracy". if it is inaccurate it may account for some of your strange readings. When you are talking ColorQ and most everyone else here is talking Taylor reagents things are bound to get lost in the difference.

As to your calcium I think Jason hit it right on the head. It is really the minerals left over when splashed water evaporates in that area. There is really nothing you are going to be able to do about this. Basic science says that when water evaporates it leaves the solids that were in solution behind (Note to self Careful with statements like this because chem geek always comes and corrects me:D). You have been cleaning with vinegar as have I in the past for similar stains. I have also used diluted muratic acid in a spray bottle and for big stains I pull out the Purity Pool OS Out Spot Stain Remover. Put it on the end of you pool pole, fill with full strength muratic acid and you can place it on stains to power them away. Now, I'm using it on tile and I'm careful to rinse the grout quickly. If this area is stone or something other than tile i would be careful cleaning with straight acid.
 
Please do not just start dumping ridiculous amounts of acid in the pool. What if the test is just wrong and your pH drops very low?

Can you give an example of exactly what you have in the calculator and what suggestion it makes so we can verify nothing is off? Do you have the borates set to 0 (assuming you have not added any)?

Next time test the pH 1 hour after you add the acid and report back.
 

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3 quarts of 29% hydrochloric acid in 19,000 gallons would lower the TA by 18.2 ppm. That's a chemical fact. If you aren't measuring this sort of drop, then something is wrong. Either the acid isn't as strong as you think or your measuring equipment is inconsistent or the water didn't get mixed well. The pH may not drop as much as predicted because carbon dioxide outgassing will tend to make it rise and there is more outgassing as the pH gets lower, but it does seem as if the acid isn't as strong as labeled (which would be strange unless mislabeled because acid doesn't go "bad").

You can validate your testing via the 100 ppm TA Standard Solution, the 200 ppm CH Standard Solution, and the 50 ppm CYA Standard Solution.
 
Today's readings are: Water Temp 79, FCL 4.10, PH 7.7, ALK 95, CH 252, CYA 43, and CSI -0.11 ("balanced" on PoolMath). On Monday (9/22) I had a PH reading of 7.8 and ALK of 93. I added over 3 quarts of 29% acid and went out of town, thinking the 3 quarts of acid would reduce the PH enough to lower the ALK reading. Upon my return, the PH was 7.6 and the ALK was 91. Today (Saturday), the PH is back up to 7.7 and the ALK is all the way up to 95, which is higher than it was before I added the 3 quarts of acid. Why did I use PH of 6.9 as a goal? Because every time I add the "right" amount of acid according to the Pool Calculator/PoolMath, I never get the change that the calculator tells me I'm going to get. The change occurs but it's always way less than expected. I was using 6.9 to overshoot in order to get the calculator to tell me to put ENOUGH acid in the pool to effect the change I wanted so I could reduce the ALK. Even then it appears to have been insufficient.

The advice to check the PH an hour after adding the acid was a good idea, but right now I have other commitments. I'll test again tomorrow and give this a try.
 
I think your problem is the method you are testing. The results are illogical. The TA must go down and will not go back up unless you are adding baking soda or adding high TA water.
 
The TA is not changing all that much and is probably well within the error range of the test.

One reason that might be leading to you not getting the calculated drop in pH is that the volume of your pool might be different than the amount you are using. If all of your adjustments for any chemicals you add are coming up short, then I would say your pool volume is off and the volume is larger than what you are using.

A few other reasons for not seeing the calculated drop are: testing accuracy, acid strength is not right, or there are borates in the pool and you are not accounting for.

You need to test an hour after adding the acid to make sure you are reading the most accurate change that the acid makes.

Do you have an auto-fill on the pool?
 
All right, I just ordered a TF-100 test kit and Speedstir. I will find out soon enough whether my testing is the problem and call the pool company once again to check the volume, then post again with some results. Yes, there is an auto-fill on the pool. The city water passes through two filters and then through a water softener before entering the pool water. It may be alkaline water, though.
 
johnsimion said:
All right, I just ordered a TF-100 test kit and Speedstir. I will find out soon enough whether my testing is the problem and call the pool company once again to check the volume, then post again with some results. Yes, there is an auto-fill on the pool. The city water passes through two filters and then through a water softener before entering the pool water. It may be alkaline water, though.
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When you talk to the pool company verify how they calculate the volume. Some give a number as if the pool were filled right to the top of the coping even though the normal water level could be well below that level.
 
Turn off the auto-fill for a week and see how much fill water is being added and test the fill water for pH and TA. Try to test the pool water everyday if you can to get a baseline for the week.
 
I had the LaMott Color-Q Pro 7. All my test results were all over the place. I was told by the State of Minn. Health Inspector that I should consider the Taylor-2006 test kit for water balance as the Color Q tester was affected by light rays interfering with the readings. I have been very impressed with this test kit, if you can count you can have great success and accuracy with the 2006 test kit. We had to drain our pool as well this summer for some painting and had to balance our water as well. We didn't use soft water to fill and it was a chore to get our Alkalinity in check but after 4 cases of Muratic Acid, we are ready to open with perfectly balanced water. I totally recommend the Taylor 2006 test kit.
 

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