Visible algae, need help please!

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Monkeydoodle08

Member
Jun 9, 2023
11
Arizona
Surface
Vinyl
Chlorine
Liquid Chlorine
Hello,

I have a 3600 gallon abive ground pool that is 2 years old. I didnt have many problems with it last year but this year I am ready to drain it and get rid of it. Everything was fine but the last 2 weeks or so there has been some algae growing. I have been adding shock, brushing it and it goes away only to return in a few days. I am using the HTH 1275 Swimming Pool Care 6-Way test kit, which is new to me this year so I hope its pretty accurate. These are my readings today.

Chlorine-2
pH-7.5
Alkalinity-50
Hardness-150
Cyanuric Acid- the kit goes to 40 and the dot was still a a little bit visible at 40.

We have had an extremely hot summer this far temps between 115-118 for the last 2 weeks or so, which I am sure is affecting things but I dont know what else to do. It seems like I am throwing away money on chemicals but nothing seems to remedy the situation. Any suggestions would be greatly appreciated. Thank you.
 
The reason that you have algae is that your FC is not high enough based on a CYA of 40 (or higher).
The CYA test only shows 0-10, 20-40 and >40. So I don't think you actually know your CYA. If you do not know your CYA then you cannot properly set a FC target and since you have visible algae, you cannot perform a SLAM Process correctly.
Also the FC test only goes to 5 and for a SLAM (assuming CYA is 50) you need to test FC up to 20ppm.

So the decision is if you want to do a proper SLAM to rid the pool of algae, then you need to purchase a proper test kit that allows you to test CYA from 20 to 100 and FC above 20.
Refer to the Test Kits Compared
Also on TFTestkits.net they sell individual test kits for CYA and FC, but it may be best just to purchase a complete kit.

Furthermore you have denoted specific data for TA and CH but the test vial only shows ranges so I am not sure those are accurate.
I am looking at this kit which has the same name you have given
hthpools.com

HTH® Pool Care 6-Way Test Kit

Quickly and easily test your indoor and outdoor swimming pool water for 6 key elements and get the most accurate results. Tests for total chlorine, bromine, pH, total alkalinity, total hardness and cyanuric acid (CYA) levels Compatible with all swimming pools
hthpools.com hthpools.com
or
 
Well, it seems your Free Chlorine (FC) level is too low compared to your CYA level. Have you always been using Liquid Chlorine to sanitize the water?
While your pool is small, it still needs to follow the FC/CYA guide to avoid algae. Here it is:
LC Chart.jpg
So for your perceived CYA of 40+, you can see that ideally your FC should be kept between 5-7ppm or even higher. The sun will always burn some off daily, so you have to have enough to cover that. In your area its probably a loss of ~4ppm per day. So keep your FC higher.
With a pool your size the fastest fix is to drain and then scrub the walls with diluted bleach water. Then follow the above chart from then on.

Maddie :flower:
 
Given the volume of your pool, you can chose to handle your pool as temporary/seasonal pool or a regular pool. As a temp pool, you would drain and start over. As a regular pool you would complete the SLAM Process. To do so, you would need a test kit capable of accurately measuring FC levels greater than 10 ppm like the Taylor FAS/DPD FC-CC Chlorine drop test.

You are likely seeing algae because your FC is too low for your CYA level. With a CYA of 40, target FC levels are 5-7 ppm and should never fall below 3 ppm.

Check out the link on temp pools:

www.troublefreepool.com

Guide for Seasonal/Temporary Pools

Smaller seasonal pools can see just as much enjoyment as their larger counterparts. In this guide we'll show you how to maintain your temporary pool.
www.troublefreepool.com www.troublefreepool.com

You should be able to get by with your existing kit if you choose.

Spend a bit of time reviewing some articles in Pool School:
Pool Care Basics
 
YippeeSkippy said:
Well, it seems your Free Chlorine (FC) level is too low compared to your CYA level. Have you always been using Liquid Chlorine to sanitize the water?
While your pool is small, it still needs to follow the FC/CYA guide to avoid algae. Here it is:
View attachment 515907
So for your perceived CYA of 40+, you can see that ideally your FC should be kept between 5-7ppm or even higher. The sun will always burn some off daily, so you have to have enough to cover that. In your area its probably a loss of ~4ppm per day. So keep your FC higher.
With a pool your size the fastest fix is to drain and then scrub the walls with diluted bleach water. Then follow the above chart from then on.

Maddie :flower:
Click to expand...

Thats the problem, I cant seem to keep enough chlorine in the pool no matter what I do. I have gone back and forth between liquid and the tablets, it honestly just depends on what is the best deal at the time. I know my pool is small, I didnt have many options for my backyard lol, and I know it would be ideal to drain it and start over but just did that about a month ago to move the pool, so that is really not an option right now. Up until recently, the levels have been ok according to the test kit anyways. I have always tried to keep my FC between 3-5. I added shock to it a few days ago which put my FC up to at least 5 per my kit, and the next day it was down to bascially 0. I honestly am so frustrated at this point. I have spent countless hours reading the forums and articles here and on other sites and was just starting to feel comfortable with everything, but now I am questioning everything I thought I understood. Maybe reading too many different articles on too many different sites has me all confused. I dont even know where to start at this point. I guess I need a new test kit, but I dont know what to do with the pool in the mean time.
 
The chemistry itself is pretty simple. With a CYA level at 40 ppm, you need to target 7 ppm FC daily. Most pools use up to 4 ppm per day. With a proper FAS/DPD test kit, you could adjust that number with accuracy to ensure your pool does not fall below minimum levels. You would test daily, and add chlorine daily.

Curious why you are hesitant to drain? In my area, water is billed per 100 cubic feet, or 748 gallons. Even during the worst times, water costs less than $2.50 per unit (748 gallons). It's much cheaper than purchasing the chlorine necessary to complete a slam.
 
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Additionally, I would recommend adding granular CYA and dosing with liquid chlorine. Solid forms of chlorine are slow to dissolve and may not provide the level of FC needed on a consistent basis.
 
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Rancho Cost-a-Lotta said:
The chemistry itself is pretty simple. With a CYA level at 40 ppm, you need to target 7 ppm FC daily. Most pools use up to 4 ppm per day. With a proper FAS/DPD test kit, you could adjust that number with accuracy to ensure your pool does not fall below minimum levels. You would test daily, and add chlorine daily.

Curious why you are hesitant to drain? In my area, water is billed per 100 cubic feet, or 748 gallons. Even during the worst times, water costs less than $2.50 per unit (748 gallons). It's much cheaper than purchasing the chlorine necessary to complete a slam.
Click to expand...
I dont know if that is an accurate level for the CYA if my test only does 40-100 and I could still see the dot at 40. The cost of the water is minimal and I am not concerned with that, they charge us more for "fees" and taxes than the actual cost of the water. Arizona has some pretty serious drought issues, so I try to do my part to conserve and I have alot of Chlorine/bleach that i have already purchased as well. If draining it is truly the easiest way then I will do that I just was hoping there was another way to remedy the situation. So in an ideal situation what should my levels be for everything just to make sure I am understanding. Also which CYA liquid chlorine would you recommend there are so many brands/options available.
 
For CYA, don't sweat the test too much. There's no CYA in tap water. On a fresh fill if you add 40 ppm based on volume (use PoolMath) that's how much will be in there. Levels will decrease over time due to oxidation and splash out. However, if you continue to dose FC based on 40 ppm, you'll never be too low. As I said earlier, I would recommend the FC drop test Taylor K-1515).
 
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That's it. The kit will allow you to precisely measure FC levels up to 50 ppm. In this test, drops are added to a sample until the sample turns clear. A formula is used to determine FC from the number of drops to clear.
 
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