OK, where did this calcium come from?

[chiefwej]

I was planning on having an RO treatment done to reduce my CH level, which had gotten over 1,000. The local company after giving the run around for a month called last week and said the pump was out on their equipment. They would have to reschedule, date unknown.

I tested my tap water (as the CH varies time to time) and the current CH was 150. So, I decided on a full drain and refill. I fully drained the pool and rinsed it down (didnt pressure wash or acid wash) and refilled the pool. There was no perceptible scale on the pool. I added my chemicals, 400 lb salt, 10 lb CYA, 14 boxes of borax, and 4 gallons of muratic acid to rebalance pH. Time to do a full battery of tests on my new water.

Now I do all my tests and my water has a CH of 250. How did it go from 150 at the tap to 250 in the pool?

I could see it going up if there were a lot of scale on the pool and/or I had the CSI negative for some time. But, neither is true and the water has only been in the pool a couple days.

 

[duraleigh]

Since you didn't put any in (except for the 150 in your fill), it had to already be there. Most likely precipitated onto the walls which didn't get fully cleaned and then dissolved back into solution.

Regardless, it is there and it will probably continue to slowly increase.

Testing error possibility always exists but probably not nearly that much.