Hello, please help me get rid of green algae!

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novata

Member
May 27, 2020
21
Sugar Land, Texas
Hello,

I have a 18,000 gal inground pool. My pump is a Pent Air with cartridges filters. It has a green algae problem. The problem started 3 weeks ago. I don't have a test kit, I've ordered one. I went to the pool store and they gave me a recipe that has improved a little the initial greenish but I still see the algae enjoying my pool. Last night I put the following: Four 1 pound bags of shock (Calcium Hypochlorite 73%), plus 2 jugs of bleach from Home Depot. Today's pool values from the store water test are as follow:
FC: 0.15
TC: 0.41
pH:6.9
TA: 62
CH:140
CYA: 76
Phosphates: 586

Today the store suggested to add products to rise the alkalinity and calcium hardness. I asked about FC, I still have the algae problem, but they said I should worry about the other two parameters first (?). Please help.

Thank you!
 
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First order the TF100 test kit sold here. If available get rush shipping. Do your own tests. Also read the pool school here. Only use liquid chlorine. Powders and tabs are likely to have CYA, and you already have too much of that. I'm assuming you don't have a salt water chlorine generator. Around here (I'm in Katy) I find Leslie's 4-gallons of 12.5% chlorine is cheaper than Home Depot or Walmart when the percent of chlorine is taken into account. I paid 16.99 at Leslies on Westheimer Parkway in Katy for four gallons of 12.5% yesterday. Calcium chloride to increase CH. Your unbelievably low pH plus low CH means you're probably losing calcium from the pool walls unless yours is a vinyl liner or fiberglass pool. Nobody here cares about phosphates as far as I can tell. Killing the algae is your need, but you might want to get the pH up a bit first, since when you run really high chlorine levels (which you will need with your CYA to kill the algae) you cannot get accurate pH readings. See the pool school on SLAMming asap. Basically, you're talking about a lot of chlorine added frequently until you stop losing it overnight. It's 1:10pm by my watch. If you hurry, you can get a box of four gallons before rush hour.

Someone smarter than I will shortly step in with what I've left out or stated incorrectly. Get the liquid chlorine while you wait for that smarter reply.
 
We can certainly help you get control of your pool, but we don't trust pool store testing so I can't really give much advice off of that. While you wait for your test kit to arrive, you can use PoolMath and add 5ppm worth of liquid chlorine to your pool every day. This won't really fix your problem, but will keep it from getting worse while you wait. You will also want to source some liquid chlorine for your SLAM.

What is your pool surface? Fiberglass, vinyl liner, plaster?
 
Thank you both for your replies. I'm expecting my kit by June 1st (I already ordered the Taylor K-2006 test kit before coming to this forum). I'm trying to understand the Pool Calculator... how can I translate how much chlorine do I need to put in my "plaster" pool ( when I bought the house the plaster was long gone, now it's just concrete). I mean how many jugs of liquid chlorine do I need to use? And what product should I use to rise the ph? (I'm sorry I'm reading and trying to understand everything from this website).. Thanks!
 
If you use the PoolMath
App you can setup your pool- aka gallons etc. & it will populate the amounts for you - you will have to put in some info to do that & know what percentage you’re bleach is65D6B3B1-9277-47B6-BC78-0A30E49BC328.pngFFD87ACE-784F-4D1C-B65E-F999275E57A5.png
 
With a plaster pool you will need to raise your CH a bit too (assuming the pool store test is accurate), so if Cal hypo is what you have on hand, just add 1lb per day until you get your kit. Each 1lb bag of 73% cal hypo will raise your FC by 4.8 and your CH by 3.4.

You also mentioned jugs of chlorine from Home Depot. If you are talking about the pool chlorine and not laundry bleach, then they are 10% strength. 1 gallon will raise your FC by 5.6 so you could do a gallon a day until your kit arrives.

For pH, we don't generally recommend chemical additions based on pool store testing. We don't trust that pool store testing is accurate. Assuming it is accurate, it's also pretty close to what you need to start your SLAM anyway. We can help you fine tune your chemistry once your kit arrives.

If you would prefer to use PoolMath on a computer, there is a link to the old poolmath webpage at the bottom of the page, otherwise you can download the app to your phone.
 

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If you got the Taylor K-2006 and not the K-2006c, order some refills on the FAS-DPD components now. You don’t get much without the C in the kit and you will probably run out quickly. :)
 
novata said:
Hi again, I'm trying to clean the filter cartridges. I'm just using pressure water, but the algae is stubborn. I don't know how to clean them properly. Please let me know. Thank you in advance!
Click to expand...
All you need to do is hose them off with the jet attachment on a garden hose. You will kill the algae when you perform the SLAM so i wouldn't worry too much about that right now. If your pressure does not go back down all the way to your normal clean pressure after you hose it off, then you will need to do a deeper clean (details in the link).

Maintenance and Cleaning of Pool Filters
 
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Hello,

I just received my Taylor K-2006 kit! These are the values I got:
Date
5/29/2020​
FC
0.4​
CC
0.4​
pH<7.0
base demand9 dropsto reach 7.2
total alkalinity CaCO3
90​
calcium hardness
270​
cya
75​

I had trouble with the CYA measurement. It depends on light (outdoors vs indoors). Also, the pH value I got didn't match any of the colors on the chart, so by the shade I assume it's lower than 7.0. I have been adding liquid chlorine and brushing daily. The pool is still green (light green now) and very cloudy.
I hope you can help me! I've attached a pic of the pool. Thank you in advance!
 

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Can you aerate to bring up ph - turn your jets up & run any water features - you just need to get to 7.2 so you can begin SLAM Process
*EDIT*
Did your kit come with the base demand table? If so add the corresponding amount of soda ash to raise to 7.2
It looks like this 0072AD73-401D-45DD-8CDA-9D8B2D8B0241.jpeg0072AD73-401D-45DD-8CDA-9D8B2D8B0241.jpeg- you’ll need to buy 2 boxes - they have it at Walmart- I would aerate until it gets added - also just keep adding 3-5 ppm of bleach until u get the ph up
 
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Hello again!,

I wanted to share my progress. I started two days ago the SLAM process. I used the CYA chart to reach 30 FC. I've been brushing my pool and cleaning my cartridge filters more than 3 times now. I see a lot of progress. The water is much clearer now, but today, after measuring FC, I added the required amount of liquid chlorine and immediately the water turned green. Please if you could advice what do I need to do know.

PS: I'd like to know if it's normal that my FC drops very quickly (half day?) and i have to replenish chlorine very fast?. Also, my CYA level is different today because other reader's eyes (my son's) Thanks!

Date
5/29/2020​
5/29/2020
5/30/2020​
5/31/2020​
Time
11:45 AM​
7:00 AM​
10:43 AM​
FC
0.4​
0.2​
0.2​
0.6​
CC
0.4​
0.4​
0.6​
0.6​
pH<7.0
7.4​
7.2​
(in between 7 and 7.2) ~7.1​
base demand9 drops
total alkalinity CaCO3
90​
125​
100​
150​
calcium hardness
270​
250​
250​
275​
cya
75​
80​
65​
 
I would say yes keep the chlorine up but adding bromides may have complicated things. How much did u add? If it was a lot I would think about replacing some water (like at least 50% enough to get cya down to a reasonable level like 40 & help remove the bromine u likely created) kill 2 birds with one stone - it would really make your slam & maintenance more efficient
@JJ_Tex @IceShadow thoughts?
 

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