I've browsed these forums regularly for the past few years when I bought a house with a pool, but this is the first time I've needed to post looking for advice.
This year I have just started having problems with my water turning green whenever I top off the pool with water from my well. I have never had this problem before. The main thing that has changed from previous years is I installed a SWG last August. The water doesn't turn cloudy, it just gets a green tint. The amount of green is proportional to the amount of water I added. Adding a 1/4 inch to the pool turned it a light green for about 2 days. I just recently added about 1" and it started turning green while I was adding the water (over a 4 hour period).
I checked all my levels before and after adding the 1" of water this time
Total Hardness: 260ppm
Total Chlorine: 4ppm
Free Chlorine: 4ppm
Total Alkalinity: 130ppm
After water turned Green:
Total Chlorine: 3ppm
Free Chlorine: 3ppm
all the rest were unchanged.
The pool is still green 48 hours later. The TC/FC are back up at 4ppm.
Based on what I have read on this site, I was suspecting this was metal in the water, though the last time I had my well water tested, it had no measurable iron in it. Just now I notice a little bit of brownish/yellow patches clinging to the walls of the pool. Algae? Could algae be coming in with the water and it just takes the chlorine in the pool a little while to kill it? What can I do to keep the pool from turning green whenever I add water?