I've been getting some greyish powder/dirt collecting at the bottom of my pool since last summer. Its definitely powder/dirt because as soon as you touch it, it disperses into the water. It also vacuums right out very easily on drain. I thought it was the sand in my filter getting old and letting fine particles through (the previous owner had a new filter installed in 2009 and the sand hadn't been changed since then). So I had the sand changed a few weeks ago, vacuumed the pool and everything seemed fine, I wasn't getting any greyish powder forming at the bottom. However one day last week, I applied some algaecide as regular maintenance (about 1 liter of 15% HTH Algae Stop). Later in the evening I put in my granulated chlorine as usual. The next morning my entire pool was a grey cloud!! I couldn't see more than 2-3 inches into the water. It took a few days for the water to clear out (I applied some HTH shock and ran the filter 24 hrs a day) but the grey powder was back with a vengeance all along the bottom of the pool.
I called the company that had changed my sand and asked them if it was due to the new sand filter. They came to look at the grey residue and said it looked like a water chemistry problem and probably had nothing to do with the new sand. They didn't think it had anything to do with the Algaecide I applied.
I know my water hardness (calcium) levels have been quite high since I bought the house. On the last reading it was close to 600ppm. I was usually able to lower it by draining off water and then adding new water but this year it hasn't seemed to help.
Any chance my high levels of calcium are causing this greyish powder problem? If not, any other ideas?
Thanks in advance.