Total Alkalinity..310ppm on a 30,000 gallon pool
by Deb Miller
My pool total alkalinity is at a 310 and pool is cloudy. All other chemistry is fine. I was told to add 4 gallons of muriatic acid 3 times a day and retest. I think this sounds like a lot of acid to put in my pool.
I have owned the pool for 10 years and have never had a problem like this. The pool supply store was stumped by the alkalinity level and said there has to be a source but they are not sure what it would be.
I am reluctant to put that much acid in my pool. We did put in 1/2 gallon about 48 hours ago and it seems a bit less cloudy but nothing significant. I was told there would be immediate results. Is it safe to do this and how long does the acid take to work?
Thanks for your questions Deb
When you adjust your total alkalinity you need to keep an eye on your pH level as well. pH is the opposite side of the same coin with your pool alkalinity.
Adjust Your Total Alkalinity
Swimming Pool pH Levels
The best range for total alkalinity is between 80 - 100ppm. For a 30,000 gallon pool your pool guy is not far off with telling you to add 12 gallons of acid. On a 30,000 gallon pool 5 gallons of acid will bring the alkalinity down about 100ppm. You actually have 210ppm to get down to 100ppm, from 310ppm.
BUT...don't do it all at once. You don't want to over-shoot and put too much muriatic acid in all at the same time. The first thing I would do is test the tap water out of your sink. This is the exact same water that's going into your pool. If it's high then you'll know the reason why the pool's total alkalinity is high.
Your local water company might be doing things with the water. Use a good Taylor Reagent FAS-DPD K-2005 or 2006 pool water testing kit. This will give you the most accurate readings.
It's the one I have always used, the one most pool professional use, and the Board of Health for Oregon when they test our pool water.
Swimming Pool Water Testing Kit
Alkalinity doesn't just go through the roof for no reason, there has to be an outside source, i.e. using too much sodium bicarbonate or high alkalinity fill water. I would be cautious when adding that much acid at once. Maybe 1 - 2 gallons at a time, then re-test. At the YMCA pool I have to periodically raise the pool alkalinity using sodium bicarbonate because our fill water has
a pH level of 8.0ppm and alkalinity of 30ppm.
We have the pool closed each Tuesday and Thursday from 8am - 10:30am, and this is when I make all of my adjustments. To lower the total alkalinity turn the pump motor off, pour the acid in the deep end of the pool and allow to sit for a minimum of 2 hours. You can very gently, but not too much, sweep the bottom of the pool to break up any "hot spots" of acid.
By doing this technique you're decreasing the alkalinity without much happening to the pH level. After about 3 hours, turn the pump motor back on and allow the pool water to fully circulate. This is called a "turnover", when all 30,000 gallons have gone through the filtration process.
You probably have a pump running about 40 gallons per minute. (GPM)
40 GPM X 60 minutes = 2400 gallons per hour
30,000 gallons divided by 2400 gallons per hour = 12.5 hours for one complete turnover.
After this turnover re-test the total alkalinity and make another adjustment. Keep doing this until you reach the ideal range of 80 - 100ppm. If it's a little over don't sweat it. Your pool won't explode. If you put 4 gallons of muriatic acid in 3 times per day I can almost guarantee your pool pH level is going to bottom out.
When you have such drastic and polar opposites of pH and alkalinity, it's going to take time to get things right. To get the pH level where it needs to be after adding that much acid you can go here:
Swimming Pool pH Levels
Pool pH Levels
Keeping doing these techniques to raise and lower your pH and alkalinity levels. Remember, when you do something to one side it does, although slightly, affect the other side so be patient, make small adjustments, and be sure to re-test after each complete turnover.
Concerning the cloudy pool water, be sure your pool chlorine level is between 1.5ppm - 3.5ppm and the cyanuric acid (CYA) is between 30 - 50ppm. The FAS-DPD test kit can show you how to test for the CYA.
Adjust Your Swimming Pool Chlorine
You didn't mention the kind of pool filter you have, but be sure it is cleaned and/or backwashed.
Your cloudy pool water issue should go away with proper filtration is the pool chlorine is at the proper range.
Cloudy Pool Water
I would advise you to get a notebook and record the readings, times you added the chemicals, the amount, etc...so you can have a log and see what you've done and what needs to be done in the future.