Pool turns green when adding water from my well

Jul 3, 2014
51
Hopkinton, MA
Pool Size
28000
Surface
Plaster
Chlorine
Liquid Chlorine
Hi All,

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

Starting:

Total Hardness: 260ppm
Total Chlorine: 4ppm
Free Chlorine: 4ppm
PH 7.6
Total Alkalinity: 130ppm
CYA: 60ppm

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?

Thanks!
 
Welcome to TFP!

Are you using sequestrants?


Thanks! I'm not using any sequestrants. I would not expect the metal content of my well water to change significantly from year to year, so I am confused about why this is just now a problem. Could it be that previous years before the SWG I was running a lower FC and CYA and their levels were low enough to prevent this reaction. Could the salt in the pool react with the metals?
 
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