ejcom12

New member
May 7, 2022
4
San Antonio, Texas
Pool Size
40000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello. I'm new to the site and to the TFP method and I'm hoping someone can let me know if I'm on the right track to treating what I think is mustard algae.

I recently fired my pool maintenance company for a number of reasons, including the persistent algae on the southern, shady walls of our pool. This led me to purchasing a TF 100 kit and reading everything I can on the site.

When I started, I found that the CYA was at 18, so I purchased stabilizer to bring it up. I completed the following test after stabilizer was added, and also had Leslie's test the water as I'm not super confident in my test ability yet.

FC 2.5
CC 1
TA 130
pH 7.8
CYA 28 (Leslie's showed 33)
CH 450

I decided to begin the SLAM method, thinking that my CYA was close enough to the lower limit of 30 when averaging my score and Leslie's. After adding the appropriate chlorine on Monday afternoon, I took the FC up to 14, CC at 0.5. The next morning the FC reading was at 13, and CC was 0. The water was clear so I thought that I had passed the OCLT with a drop of 1ppm in chlorine over night.

From there, I took the chlorine level up to Mustard Algae levels recommended by my CYA level. After adding more bleach, at 4pm yesterday I tested FC at 19 and CC 0, with lots of brushing. By 8:30 last night the FC was 16.5 and CC at 1, so I added more chlorine again.

This morning I did the full slate of tests and here's the results:

FC 16
CC 0.5
TA 110
pH 8.2
CYA 22
CH 600

I believe the pH isn't a concern because I'm at such high FC levels, but the CYA dropping like that is puzzling. CH coming up to 600 is a bit confusing too.

I've attached a before and after of what I think is mustard algae. The first two pictures were taken May 7th, the second pics are taken this morning. It doesn't seem like I'm making much progress.

Any thoughts on my next steps? Should I drop back down and try SLAMing again after a few days? The one step I know I'm missing is taking the lights out of the niches. I got lazy on that step since I actually have to get in the pool to remove them, but I can do that as well.

Do I give up and head back to Leslie's? :(

Thanks for all the great advice on this website!
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
40,605
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Welcome to TFP! :wave: One thing for sure, you can skip Leslie's. That is no help at all and can actually confuse you. Now that you have a TF-100, that's all you need along with perhaps some coaching and confidence in your testing.

The light niche, that's a must. Any algae in there will continue to give you problems. With the breaker to the light off, pull the light and leave it on the decking for a couple days. That stuff on the southern walls I see in the pic ... it brushes off easily, or is it embedded? Remember that the OCLT inly applies to regular SLAM level. We only go to MA levels after passing all 3 SLAM criteria, and even then that MA level is only for 24 hrs. I wasn't sure if you followed that protocol. Today should be a good sunny day to get a good CYA reading. The dot must disappear by 30. If you still see the dot, add about 10 ppm worth of stabilizer (sock method). Even if you accidentally pushed the CYA up to 40, the SLAM FC level would only be 16 and still very manageable.

If this truly is Mustard Algae, every inch of the pool must be exposed to chlorine and brushed really well. If you haven't done so already, you might pull the drain cover off and clean in there as well. If you have any other questions let us know.

 

ejcom12

New member
May 7, 2022
4
San Antonio, Texas
Pool Size
40000
Surface
Plaster
Chlorine
Liquid Chlorine
Welcome to TFP! :wave: One thing for sure, you can skip Leslie's. That is no help at all and can actually confuse you. Now that you have a TF-100, that's all you need along with perhaps some coaching and confidence in your testing.

The light niche, that's a must. Any algae in there will continue to give you problems. With the breaker to the light off, pull the light and leave it on the decking for a couple days. That stuff on the southern walls I see in the pic ... it brushes off easily, or is it embedded? Remember that the OCLT inly applies to regular SLAM level. We only go to MA levels after passing all 3 SLAM criteria, and even then that MA level is only for 24 hrs. I wasn't sure if you followed that protocol. Today should be a good sunny day to get a good CYA reading. The dot must disappear by 30. If you still see the dot, add about 10 ppm worth of stabilizer (sock method). Even if you accidentally pushed the CYA up to 40, the SLAM FC level would only be 16 and still very manageable.

If this truly is Mustard Algae, every inch of the pool must be exposed to chlorine and brushed really well. If you haven't done so already, you might pull the drain cover off and clean in there as well. If you have any other questions let us know.

Great to have a response from a neighbor in the SA area! Thanks for your help. I definitely need to build confidence in my testing.

I believe I passed the OCLT: The water was clear, my morning FC test indicated a 1ppm drop, from 14 to 13, and I didn't have any CCs.

Okay, I will take the lights out and clean the drain as soon as I get home. Is it safe for me to get in the water with the chlorine that high? I'm assuming hustle into the shower immediately afterwards?

After that, what do I do next? Maintain mustard algae level? Drop down to regular SLAM level?

Thanks again!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
40,605
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Is it safe for me to get in the water with the chlorine that high?
It is safe as long as you haven't exceeded your regular SLAM level. You can't go in if the water is at MA level. So if your current SLAM level is 12, and you are 12 or below, you can get in there and check the lights/drain. Post swim shower optional. Ha.
 

red-beard

Gold Supporter
May 27, 2019
1,619
Houston, TX
Pool Size
25000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
Brushing, looking for any location where algae can hide. The pool cleaner. Make sure the filters are clean. put EVERYTHING in the pool when you get to the MA level to make sure everything is exposed to the very high FC level.

And once you are done with the SLAMs, keep the FC to the high side of your range. If your CYA is 30, the range is 4-6 ppm, BUT for a while keep it at 6 ppm, or so that it is 6 ppm at the end of the day. That means dosing to 6+ what you lose in 24 hours. You will probably be dosing to 8-9 for a few weeks. I've been doing this for about 2 years...I hat Mustard Algae!
 

ejcom12

New member
May 7, 2022
4
San Antonio, Texas
Pool Size
40000
Surface
Plaster
Chlorine
Liquid Chlorine
Brushing, looking for any location where algae can hide. The pool cleaner. Make sure the filters are clean. put EVERYTHING in the pool when you get to the MA level to make sure everything is exposed to the very high FC level.

And once you are done with the SLAMs, keep the FC to the high side of your range. If your CYA is 30, the range is 4-6 ppm, BUT for a while keep it at 6 ppm, or so that it is 6 ppm at the end of the day. That means dosing to 6+ what you lose in 24 hours. You will probably be dosing to 8-9 for a few weeks. I've been doing this for about 2 years...I hat Mustard Algae!
Sounds like a plan I can follow. Thank you!
 
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