Old pool...New owner...Stat heavy...looking for balance advice

[sox6035]

First of all, first post and glad to be here. Pool is 30+ y/o concrete approx. 37K gallons well maintained through the years. Pool was opened and treated by local company this Spring and they did a great job getting it to swimming condition. I'm looking eing said, pool seems happy to use the BBB method this season and looking to share stats for some advice on the next step.

pH: 8.4
Chlorine: total- 9.5 Free-7.8 (20 hours after shock) .3 and 0 pre shock
Alkalinity: total- 122 Free-99
CYA: 76

With the above being said, the pool seems happy (before shock anyway). I have the following questions:

1) How long after shock should I expect the chlorine level to equilibrate back to maint. levels (given typical NE weather)?

2) How much should I fight the pH? (I read the cited article about a higher pH and my take is that I should adjust the alk and chlorine and let the pool reach its "happy" pH).

3) I have not found "doses" of the BBB's to start off (per 10,000 gal.) anyone care to make suggestions (no borax for now...I know)?

Again, thanks for reading and look forward to learning a ton this season....and hopefully not having any huge issues in the process.

[Mftek1]

Hello!

High chlorine levels can give you a high/unaccurate ph reading.
After shock it could take about 8 hours, even more for the chlorine level to come down.

Once your chlorine is at a stable reading (2-3.0)
You can test the ph and alkalinity again.

If your ph and alkalinity are still high you can add muriatic acid to lower both numbers.

Post back and let us know what happens! Thanks.

[Watermom]

First thing that you should do is order a good test kit. The one we recommend is the Taylor K-2006 or 2006C which you can get through the test kit link in my signature below.

You also should read the Best Guess Chlorine Chart in my signature to learn about the connection between CYA levels and needed chlorine levels.

There is no way to determine how long it will take for chlorine levels to drop, but it is fine to swim with FC at 9. That is within your needed range of 5-10 per the chart.

How high was your chlorine level when you tested pH? Retest it when the chlorine drops back down. If it still that high, then you need to add some muriatic acid to lower it. (Again, read info in sig about using acid safely.) You are right that pools tend to have a pH that they like to be at, but when you retest it, if it really is 8.4, that is too high. You need to keep it between 7.2-7.8.

There is a very handy calculator (in the Forum Q & A section) that you can download to help you figure out doses of things.

Hope this helps. Let us know if you have more questions.

Welcome to the Pool Forum!

[BigDave]

The poolcare method taught here is simple, efficient, and effective. Founded in science and proved by time, the "BBB" method is really about testing the pool water and acting on your observations.

To follow this method successfully, you'll need a Taylor K-2006 (or a K-2006C - bigger reagent bottles). This is the single best poolcare purchase I've made and it's critical - accept no substitutes. If you buy it through the links in this thread the Poolforum get a few shekels to keep the lights on.

Read the guides and tips on poolsolutions.com and the stickies in the poolcare and chemistry forums here (you probably need to log out).

How do you chlorinate?

If you take a look at Ben's Best Guess Chart, you'll see that with a CYA of 76 (CYA tests are not this accurate) you are in the normal range for Free Chlorine now. With a Combined Chlorine of 1.7 (TC-FC) you do need to shock the pool. Here shock is a verb not a noun; here's a quick overview of the process:

Bring the FC above the minimum shock level (20 for CYA 76) on Ben's Best Guess Chart and don't let it drop below. Test and add bleach / LC to restore shock level at least twice a day.
Run the filter 24/7 - cleaning as needed.
Continue this regimen until one day after:
The pool loses less that 1 ppm FC between sunset and sunrise
And there is nearly zero CC (less than one drop)
And the pool is clear.

You'll need about 5-1/2 gallons of 8.25% bleach to bring your pool's FC from 7.8 to 20.

I'd also bring the pH down some with Muriatic Acid this will also have the effect of reducing the TA. Please read and understand Using Muriatic Acid to Safely Lower Your Pool's pH. If you let it get above 8.0 you won't be able to measure it and you won't be able to correct it.

[BigDave]

Sorry Watermom I was posting at the same time as you. Our advice is, I'm proud, quite similar.

[Watermom]

Not a problem! I guess that means that great minds think alike!

[PoolDoc]

Chlorine: total- 9.5 Free-7.8
Alkalinity: total- 122 Free-99
CYA: 76

You've already been given most of the info you need. But I wanted to point out that your test results tell me you are using a totally bogus computer test method of some sort or another.

Why bogus?

Very simple.

The best available field test method for CYA can barely distinguish between 70 ppm and 80 ppm, and can only do so reliably using a precision (= very expensive!) spectrophotometer. The digital strip readers commonly used by pool dealers have displayed resolutions of 1 ppm or even 0.1 ppm . . . but an accuracy of less than +/- 25 ppm. We have *often* seen CYA test errors on dealer pool test results of 30 - 50 ppm!

Please note: the digital units have an actual error value that is 20 to 200x times LARGER than the apparent resolution (and implied accuracy) shown on these god-forsaken devices!

However, because the only way pool owners come up with results like CYA = 76 is one of these digital units, we can recognize the bogus results.

Here's what your test results SHOULD be, if 'truth in marketing' were enforced:

pH: nominal value => 8.4; range of likely actual values => 8.0 - 10.5
Total chlorine: nominal value => 9.5 ppm; range of likely actual values => 6 - 12 ppm
Free chlorine: nominal value => 7.8ppm; range of likely actual values => 4 - 10 ppm
Total alkalinity: nominal value => 122 ppm; range of likely actual values => 90 - 150 ppm
Adjusted* (not: "free") alkalinity: nominal value => 99 ppm; range of likely actual values => 60 - 140 ppm
CYA: nominal value => 76 ppm; range of likely actual values => 30 - 120 ppm

* adjustment based on inaccurate CYA measurement!

Accurate measurement of CYA is possible . . . in a sophisticated lab. Here's the analysis process for CYA in the 0 - 5 ppm range with a detection limit of 0.1ppm:

Assay methodology
The assay methodology for measuring cyanuric acid in pool water samples and urine specimens have been described previously by Cantu´ et al. (2001a,b).

Briefly, the pool water samples were filtered, using an activated cellulose filtration disk, followed by dilution of a suitable aliquot with deionized-distilled water. Samples were then refrigerated at 48C in an amber colored plastic storage bottle for no more than one week before analysis. A 25 ml aliquot of the sample was directly injected into a porous graphitic carbon column for reversed phase high performance liquid chromato-graphic analysis (RP-HPLC). Separation of cyanuric acid was achieved using isocratic elution chromatography with a mobile phase of 95% 50mM phosphate buffer (pH 9.1) and 5% methanol (% v/v) followed by UV detection at 213 nm. The procedure was linear in the range of 1–5mg/l with a detection limit of 0.1mg/l. Cyanuric acid was quantified using an external calibration curve. To avoid biological and chemical degradation, the 24 hour urine sample was immediately preserved after collection by the addition of 1ml of a reagent composed of 10% (v/v) perchloric acid and 1% (w/v) metaphosphoric acid. The urine was cleaned by initially centrifuging 1.5ml of the preserved sample. Next, 1ml of the supernatant was loaded onto 3 previously conditioned, stacked, solid phase extraction cartridges. The filtered urine sample was eluted from the cartridges using 4ml of a 0.05M hydrochloric acid solution. Subsequently, 2.5ml of dichloromethane was added to 1.5ml of the filtered urine, the mixture was vortexed, and the phases were allowed to separate. A 450 ml aliquot of the aqueous phase was then transferred to an HPLC auto-sampler vial and stored at 48C. Just prior to analysis, the pH of the aqueous phase was adjusted with sodium hydroxide and the sample immediately injected into a porous graphitic column as indicated above for the pool water samples.

Please note, this method requires use of a HPLC (High Pressure Liquid Chromatograph). Here's a Google Shopping link, to give you an idea of why your neighborhood pool dealer is NOT likely to be using an HPCL:
https://www.google.com/search?q=hplc

In the wake of melamine & cynauric acid doping of pet foods and infant formula by Chinese export manufacturers, the FDA has approved an even more elaborate, accurate -- and complex -- methods of analysis:
http://www.fda.gov/Food/FoodScienceR.../ucm071673.htm

Meanwhile, we'll continue to recommend the use of the turbidimetric (cloudy water) method found in the Taylor K2006 testkit, which provides adequate accuracy (+/- 10-20 ppm) for pool operations.