Water Chemistry Within Spec but Still Green?

rofflesaur

Member
May 18, 2017
14
Pitman, NJ
Pool Size
12000
Surface
Vinyl
Total Hardness: 150 ppm
Total Chlorine: 5 ppm
Free Chlorine: 3 ppm
Combined Chlorine: 0.5
pH: 7.2
Total Alkalinity: 100 ppm
CYA: 50 ppm

For once my water is actually balanced, but my pool bottom still turns green within a day. I’ll vacuum to waste and it will look good, then 24-48 hours later it starts getting cloudy and green bottom. What gives?

Here in NJ it’s been 90-95F every day and the pool gets full sun. Water temp is 86. I’d imagine this is also ideal for algae growth.
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Here in NJ it’s been 90-95F every day and the pool gets full sun. Water temp is 86. I’d imagine this is also ideal for algae growth.
Here it is 115F and the water temperature is 92F. And my pool has never had algae.

So something is not right.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
FAS-DPD give you FC and then CC if you follow through.

Target for CYA of 50 ppm is 8 ppm FC.

Test strips are not an adequate method to test pool water chemistry. Get a proper test kit.
 
Last edited:

CuckooChris

Well-known member
Sep 14, 2016
84
Coplay, PA
Tfp isn't just a forum to ask questions, it's a method to keep your pool or spa sparkling clean. The first step is to get a good test kit, tf100 or Taylor 2006. You need to know what your cya level is in order to know what the proper chlorine level should be. A chlorine level of 3 is way too low. Don't be afraid of higher chlorine, you'll probably never tell the difference between 3 and 13.
 

rofflesaur

Member
May 18, 2017
14
Pitman, NJ
Pool Size
12000
Surface
Vinyl
FAS-DPD give you FC and then CC if you follow through.

Target for CYA of 50 ppm is 8 ppm FC.

Test strips are not an adequate method to test pool water chemistry. Get a proper test kit.
I ordered the K-2006 kit and just got it today.

Free Chlorine: 12.5 ppm
Combined Chlorine: 0.5 ppm
pH: 7.3
Total Alkalinity: 110 ppm
Calcium Hardness: 110 ppm
CYA: 80 ppm

I assume the CYA is too high? The calcium hardness also seems low according to the TFP calculator. I already dumped quite a lot (2 lbs) of calcium chloride into it last month to get it up that much. Does it have any effect on algae growth?

Thanks.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
CYA is high to SLAM. Best if you can drain off some and refill. Do not go lower than 12 inches of water left in the shallow end. Best to get the CYA down to 50 or so.

No need for calcium in your pool. You have a vinyl liner. It does not need calcium.
 

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rofflesaur

Member
May 18, 2017
14
Pitman, NJ
Pool Size
12000
Surface
Vinyl
CYA is high to SLAM. Best if you can drain off some and refill. Do not go lower than 12 inches of water left in the shallow end. Best to get the CYA down to 50 or so.

No need for calcium in your pool. You have a vinyl liner. It does not need calcium.
I'm surprised it's that high given how many times I've vacuumed to waste and added water. I'm using trichlor tablets in an inline feeder right now. After I get the CYA back to the appropriate level and SLAM, do you think I should switch to using liquid chlorine only instead?

Everything else looks okay to you?

Thanks!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I'm using trichlor tablets in an inline feeder right now.
That is adding more CYA. You need to stop using those for daily chlorine additions. Use liquid chlorine. Save the tablets for when you are going to be away from the pool for more than a few days.
 
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