JasonLion said:
The other possibility is that the PH was a bit too low for a bit too long at some point and that dissolved extra calcium out of the surface and into the water.
I think that is what happened.
Ok so just finished filling a brand new plaster pool (diamond brite exposed aggregate finish)this morning. We did an acid wash before filling then added a ton of acid after filling at the direction of the plasterer. Like 12 gal in a 16k gal pool.
Testing ph, it's lower than 6.2 using the TFP kit. (YELLOW!) and testing TA the solution turned red before I even added any of the 2nd reagent. What does the latter mean?
new-pool-1st-fill-initial-test-help-t39440.html
12 gallons of 31.45 % acid in 16,000 gallons of water will lower the TA by about 380 ppm. So, subtract 380 ppm from your fill water TA to get what your TA was. It was probably strongly negative unless the TA was above 380 to begin with.
The pH would have been well below 4.5.
This is called an acid startup. However, 12 gallons of acid in 16,000 gallons of water is very aggressive unless the acid is a lot lower strength than 31.45 %.
All of that acid would have dissolved a lot of calcium out of the plaster.
Also, if the system was online during the low pH, then there might be copper in the water from the heat exchanger, which could interfere with the calcium hardness reading.
Your posts indicate that there are metals in the water. The green water was probably from copper. Try this modified test to eliminate copper interference:
Make a sample of 50 % pool water and 50 % distilled water. Mix well. Follow these steps to test:
1) Rinse and fill large comparator tube to 25 mL mark with water to be tested.
2) Add 10 drops R-0012. Swirl to mix.
3) Add 20 drops R-0010. Swirl to mix.
4) Add 5 drops R-0011L. Swirl to mix. If calcium hardness is present, sample will turn red.
5) Add R-0012 dropwise. After each drop, count and swirl to mix until color changes from red to blue.
6) Add the original 10 drops of R-0012 to the number of drops needed in step 5, and multiply the total number of drops by 20. Record as parts per million (ppm) calcium hardness as calcium carbonate.