High Alkalinity & Cyanuric Questions
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.
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.