I've opened my pool each of the last two springs ('08 and '09) to a fairly severe case of calcium scale. In each case, my recourse was to dump the pool, let the finished surfaces air dry, remove the scale with a stiff broom, sweep it up, and refill. There was less this year than in 2008, but still a significant amount. I want very much to avoid doing that again in the spring of 2010.
First, here is some background on my pool:
20500 gallons, built in 2007 in central NJ with Hydrazzo finish, DE filter, chlorinated with the Liquidator. I use a mesh safety cover over the winter, so rain and snow melt do get into the pool.
When the pool was closed at the end of September 2008, these were the test results:
These were the test results when I opened in May 2009:
ph: > 8.0 (off scale, very bright red)
And these are my current numbers:
I've generally figured out that the reason the scaling is happening is that the pH drifts upward over 8.0 over the winter and that combined with cold water and moderate levels of TA and CH create the scale deposits.
So, here are my questions:
What is driving the pH up?
Should I close the pool with a lower pH, TA, and/or CH? If so, what levels?
Does rain water cause the pH to creep up?
Is it typical to have to monitor the pool over the winter months and amend the water for a closed pool? I don't know anybody around my parts doing that.
Thanks for any insight.