Pool turns green when adding granular chlorine

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Pool turns green when adding granular chlorine

Postby chem geek » Thu 05 Nov, 2009 11:32

If the flakes are white or gray, then it could be calcium carbonate scale. The missing measurement is Calcium Hardness (CH) since it is the combination of high pH, TA and CH that causes scale. Measure the CH and use The Pool Calculator to figure out the saturation index and if it's high, then yes it's probably scale.

It is surprising to have such a high TA and a low pH at the same time. If the pool isn't covered, then outgassing of carbon dioxide would normally have the pH rise. If acidic sources of chlorine were used, including Trichlor, then that usually results in a drop in TA over time in addition to a lower pH. Something still doesn't seem quite right here. Yes, your adding pH Up and Alkalinity Up could greatly increase the TA, but it's just strange it was high to begin with. Do you have any idea how high it was before you added chemicals?

I don't know how the Guardex test kit works, but with the Taylor kits the TA won't be clear even if it's extraordinarily high -- it simply doesn't work that way. The test indicator is nothing more than a pH indicator. High sanitizer levels can change its colors as I noted in a previous post, but a high TA has no effect on the indicator. The test simply titrates with acid and the indicator changes color at a pH of around 4.5.

If the TA were truly very high, then yes, it takes more base to increase the pH. Instead of using pH Up which increases not only pH but also increases TA substantially, you could have used a pure base such as lye / caustic soda or could have used Borax (if available). You also could have aerated the water and removed acidic sources of chlorine such as Trichlor.


BahamaPoolCleaner
Pool Newbie
Pool Newbie
Posts: 7
Joined: Thu 05 Nov, 2009 08:18
Location: Nassau

Pool turns green when adding granular chlorine

Postby BahamaPoolCleaner » Thu 05 Nov, 2009 19:21

chem geek wrote:If the flakes are white or gray, then it could be calcium carbonate scale. The missing measurement is Calcium Hardness (CH) since it is the combination of high pH, TA and CH that causes scale. Measure the CH and use The Pool Calculator to figure out the saturation index and if it's high, then yes it's probably scale.

It is surprising to have such a high TA and a low pH at the same time. If the pool isn't covered, then outgassing of carbon dioxide would normally have the pH rise. If acidic sources of chlorine were used, including Trichlor, then that usually results in a drop in TA over time in addition to a lower pH. Something still doesn't seem quite right here. Yes, your adding pH Up and Alkalinity Up could greatly increase the TA, but it's just strange it was high to begin with. Do you have any idea how high it was before you added chemicals?

I don't know how the Guardex test kit works, but with the Taylor kits the TA won't be clear even if it's extraordinarily high -- it simply doesn't work that way. The test indicator is nothing more than a pH indicator. High sanitizer levels can change its colors as I noted in a previous post, but a high TA has no effect on the indicator. The test simply titrates with acid and the indicator changes color at a pH of around 4.5.

If the TA were truly very high, then yes, it takes more base to increase the pH. Instead of using pH Up which increases not only pH but also increases TA substantially, you could have used a pure base such as lye / caustic soda or could have used Borax (if available). You also could have aerated the water and removed acidic sources of chlorine such as Trichlor.


Thanks for the detailed reply its much appreciated. Thanks!

I had another pool guy come down and check it out and he said the pump is working good but could use a good clean. He said to brush the pool and then add 3 scoops of HGH or 65% granular chlorine spread all over the pool. He said that will clear it right up. I also have the pump running 12 hours instead of 6 hrs.

The pool was painted and that stuff floating was paint. I was told (by the other pool guys that came yesterday and charge me $100 for the consultancy) that the DE filter would need to be taken apart and cleaned every week..$150 a clean. This guy is a trained technician and has worked for alarge pool company on the island for many years...he said thats non-sense and that the paint floating would not even get to the DE filter.

so thats better news. I hope the HGH clears the water and we can get the filter cleaned and everything will be smooth sailing from now on.

he also said the ph and TA will fall inline when the HGH is added. it should be noted our well water and city water is hard so this may be just a solution for the Bahamas as our water is much harder than other countries. could explain a high TA as well.
Guest

Pool turns green when adding granular chlorine

Postby Guest » Wed 06 Jan, 2010 08:19

I think your pool needs to be cleaned right away
chatfield

Pool turns green when adding granular chlorine

Postby chatfield » Fri 22 Jan, 2010 18:07

This morning i put 2 lbs of shock in my pool and within 15 mins it was a beautiful shade of green. I think that meant that the PH was too high and had metal in the water. I went to walmart and bought 12 lbs of Arm and Hammer baking soda and put about half in my pool. It took about 3 hours but my pool is crystal clear blue.....YAY!

Return to “Pool Algae & Green Pool Water”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 0 guests