High Alkalinity & Cyanuric Questions

(Neenah, WI)

I recently took over care of a 37,000 gal pool.

I'm new at this & the training I was given is limited at best. My last test had a pH of 7.5 & alkalinity of 170.

Based on what I just read it should be lower. How do I correct this? Also what is the range that the CYA should be in? My last test was 40.

Thanks for the question

I have some, but I'd like to have all of your chemical readings. The pH is fine. I ran the pH level in all the pools I took care of, including the YMCA pool, between 7.6 - 7.8ppm. 7.5ppm is just fine. I would encourage you to get a Taylor FAS-DPD K-2006 pool test kit. It will give you the most accurate readings:

Pool Water Testing

Water Testing Kit

Alkalinity of 170ppm is a little high, but nothing to worry about. It can easily be decreased by using muriatic acid.

Pool Alkalinity

Total Alkalinity

To decrease alkalinity 10ppm for every 10,000 gallons, you'll use 0.8 qts. of acid. For your size pool, to decrease the alkalinity 50ppm, you'll use approx. 3 gallons. This should be done in a series of applications, not all at once. You'll want to do this with the pump turned off.

Start out with about 1 - 1.5 gallons of acid. Add it in the deep end in one spot. Very gently brush the bottom to break up any hot spots of acid. Allow this to sit for at least 3 - 4 hours. Turn the pump back on and allow for one full turnover of the pool water. This is normally about 8 - 10 hours. Retest, and make another adjustment if needed. The links above go into much more detail.

You can make the adjustment in the evening. Turn on the system after a few hours and let it run all night. Your CYA should be between 30 - 50ppm and the chlorine level between 2 - 4ppm. The pool chlorine is 7.5% of your CYA level and the range is 30 - 50ppm. As long as you stick to the above you should be fine.

Hope this helps and if there's anything else please don't hesitate to contact me again.

You can find your post in the "Alkalinity" category on the Q&A page:

Swimming Pool Questions and Answers

Once you get the hang of it pool maintenance is very easy.

Good luck and have fun with it.


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Jan 19, 2015
Today's Pool Test Results
by: Robert

Today's test results are:

Chlorine - 3

pH - 7.4

Alkalinity - 190

CYA - 40

I have 2 Taylor Test kits, but I don't have the # with me right now. 1 tests only the Chlorine, pH & Alkalinity. The other includes the CYA test. I wasn't trained to test for Calcium Hardness & don't know how to do so. Would this test be a part of a Taylor kit? If so, which one? Does Smart Shock & Lo-n-Slo affect the alkalinity at all?

I see that when you add chemicals you should turn the filter off. Again I was not told to do this. Could this be a part of why things are off balance? How often do you recommend testing the CYA?

The chlorine, CYA and pH are very good so don't mess with those. Most good Taylor kits have the calcium hardness in them. It's a very easy test to do. The hardness test uses 3 small bottles with the blue lids.

1. Fill the large tube 1/2 with pool water and add 20 drops of the R-0010. This is the calcium buffer. Swirl to mix.

Don't shake the tube as it does nothing. You need to get a good swirl.

2. Put in 5 drops of the R-0011L. This is the calcium indicator.

It there's calcium in the water, the sample will turn red.

3. If it's red, you'll add the Hardness Reagent R-0012 1 drop at a time.

Swirl between each drop. Count the # of drops until the sample turns from red to blue. The multiply the # of drops by 10 and you'll have your hardness. If you put in 15 drops the hardness will be 150ppm. It's best to hold the tube at eye level against a white background, or as close to white as you can, while doing your chemical readings.

Smart Shock does not afect your alkalinity but BioGuard Lo'N Slo might. It contains Sodium Bisulfate which, like muriatic acid, is used to reduce both the pH and alkalinity levels.

That's why when your making adjustments to either the pH or alkalinity, it's important to have the pump on or off. I see in the question that you were told to not do this. There are many opinions, and here's mine. There's 2 ways to decrease the alkalinity. The first way is to decrease both the pH and alkalinity, then raise the pH.

You lower both, then add air into the pool through water features such as slides, waterfalls, splashing around, or using an air hose placed in the pool hooked up to an air pump. This is called aeration. This aeration burns off the CO2 (carbon dioxide) in the pool and the pH goes back up.

I had a route of around 50 pools in Arizona for years and I've been the pool operator for the YMCA for the last 3 years. We don't have any water features, I don't have an air pump, and very limited time to make adjustments. We're open from 5am - 9pm 6 days a week.

Our fill water has the pH level of 8.0ppm and alkalinity of 30ppm. If I try to raise the alkalinity using sodium bicarb. (baking soda) the pH will go through the roof. If I add muriatic acid to decrease the pH, then the alkalinity (total alkalinity/TA) will bottom out. So, what do I do?

I raise the TA with baking soda with the pump off. Allow it to sit for 3 - 4 hours, then turn it back on. When I was taking care of pools in Arizona I didn't have time to run back and forth turning on and off slides and using an air compresser.

When I need to lower the pH, I leave the pump on and add the acid around the perimeter of the pool. It works every time. You can use the first technique and it will work. But, for simplicity sake and time constraints, I choose to lower and raise the pH and alkalinity levels like I've always done.

Concerning the CYA, you should test all of your chemicals at minimum one per week, ideally twice. Hope this helps and let me know how it turns out for you.


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