Help! Green!

[e49418]

Hi all - I was away for a couple days this week and while I was gone it rained pretty hard. Pump ran for the normal amount of time while I was gone, and I have a in line chlorinator (don't judge me!).
I tested the water this morning and as I expected, the levels were not bad enough to account for the green; free chlorine was at 3.5, pH at 7.4, alkalinity a little low at 76. Since I don't yet completely trust myself, I took a sample to the local pool store (I know...) and their results were almost identical to mine.
I added about 3 lbs of baking soda as the first step. Then after four hours added two pounds of 70% cal hypo shock. It's been about six hours since I did that. No improvement yet - I didn't expect miracles!
Any thoughts on why the pool went green with fairly well balanced water?

 

[JJ_Tex]

Post up your full test results from your test kit including CYA. That will tell you if your FC is good or not.

 

[e49418]

Hi all - I was away for a couple days this week and while I was gone it rained pretty hard. Pump ran for the normal amount of time while I was gone, and I have a in line chlorinator (don't judge me!).
I tested the water this morning and as I expected, the levels were not bad enough to account for the green; free chlorine was at 3.5, pH at 7.4, alkalinity a little low at 76. Since I don't yet completely trust myself, I took a sample to the local pool store (I know...) and their results were almost identical to mine.
I added about 3 lbs of baking soda as the first step. Then after four hours added two pounds of 70% cal hypo shock. It's been about six hours since I did that. No improvement yet - I didn't expect miracles!
Any thoughts on why the pool went green with fairly well balanced water?

Test results:
FC 3.8
CC 0
pH 7.4
CH 236
TA 78
CYA 100
Temp 85

 

[JJ_Tex]

Sorry, its algae because you didnt have enough chlorine. I just noticed your pool math logs and your latest CYA is 77... which we round up to 80 CYA.

If you look at the CYA/FC chart, at CYA of 80 your FC target should be 9-11. Your FC was 3.5 and certainly well below the minimum level and allowed algae to take hold.

Read about the SLAM process several times, figure out a good source of liquid chlorine, and start your SLAM.

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

 

[JJ_Tex]

Oops, we posted at the same time but with a CYA of 100 your FC needs are going to be even higher. You may consider doing a partial drain/water exchange to get your CYA levels down.

 

[mknauss]

CH 236
TA 78

Those are not possible from a drop based kit.

 

[e49418]

Oops, we posted at the same time but with a CYA of 100 your FC needs are going to be even higher. You may consider doing a partial drain/water exchange to get your CYA levels down.

Thanks. After posting I did some more reading about SLAM and used the Pool Math app to give me the recommended amount of chlorine to add.

I’m going to do a full brushing in the morning as well.

 

[JJ_Tex]

Also, if needed here is a good article on the recommended test kits that provide the level of accuracy needed to confidently follow TFP advice. I personally recommend the TF100, but there are several others. Please note that we do not trust pool store results. They are notoriously inaccurate and their real motivation is to sell you stuff vs actually caring for your pool.

Swimming Pool Test Kits Compared

What pool test kit should I buy? Why not use test strips? Our recommended test kits will pay for themselves in no time!

www.troublefreepool.com