SWG Algae Solved - but what happened?

[niveknow]

My Pool: 26k gallon outdoor SWG pool. 5 years old. Pebbletech

Problem - black algae on bottom at various places. IMHO not major, but the Mrs. thinks the sky is falling.

What I've done (unsuccessfully)
- Shock Calcium Hypo (double and triple dose)
- SLAM - this includes adjusting CYA and all the other stuff along with SLAM recipe.
- Scrubbed like heck before SLAM and shock. This is tougher with pebbletech because it's not a smooth surface that you can easily scrub even with a wire brush without totally destroying the surface.
- Raised FC levels to 3-5ppm by running SWG higher
- Added trichlor pucks in a floater

It's almost an annual battle and each year I try something new each year with the above tweaks all unsuccessfully. Well, I guess that's subjective because it's Not that bad which might suggest my actions did help, but I think I figured it out: trichlor (53%) granulates. I grabbed a handful and dropped it from the surface and watched it sink presumably dissolving some, but some granules able to make it to the bottom and lay directly on the algae. Pump off to allow it to settle but it seems to turn all the black into brown in a matter of hours. The brown I read is dead algae. I was hesitate to do this before because I didn't want the chlorite to bleach or discolor my pebbletech, but that 53% gave me a little confidence that it might be low enough not to be a problem. I tested a small section first overnight before I decided to continue this morning where I noticed how fast this works.

So here's the question: why? I've raised the FC high relative to CYA during slam. Did all the crazy amounts of shock. Nothing worked, but was this simi undissolved and scattered trichlor granules packed enough punch to knock it out in hours because of the concentration? Is the chlorine in the trichlor different than what comes out of a SWG?

 

[PoolStored]

I've raised the FC high relative to CYA during slam. Did all the crazy amounts of shock. Nothing worked, but was this simi undissolved and scattered trichlor granules packed enough punch to knock it out in hours because of the concentration? Is the chlorine in the trichlor different than what comes out of a SWG?

The granular "sprinkle" method is one that @1poolman1 recommends, however he recommends calcium hypochlorite granules. No difference really, just that trichlor adds cya and cal-hypo adds calcium. SWG and all these products create the same sanitizing results.

The other method, advocated by @Katodude is to use a power washer (lower pressure the better and wider tip, starting far away from the spots and moving in until it starts to blow the algae away). The get a pressure spray pump, fill with the strongest liquid chlorine you can find and spray the areas with the LC with the pump off. Then need to run your FC at 20% of your CYA for several weeks.

Either way, you probably need to run FC at 15% of CYA for life of this plaster.

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

www.troublefreepool.com

 

[1poolman1]

The granular "sprinkle" method is one that @1poolman1 recommends, however he recommends calcium hypochlorite granules. No difference really, just that trichlor adds cya and cal-hypo adds calcium. SWG and all these products create the same sanitizing results.

The other method, advocated by @Katodude is to use a power washer (lower pressure the better and wider tip, starting far away from the spots and moving in until it starts to blow the algae away). The get a pressure spray pump, fill with the strongest liquid chlorine you can find and spray the areas with the LC with the pump off. Then need to run your FC at 20% of your CYA for several weeks.

Either way, you probably need to run FC at 15% of CYA for life of this plaster.

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

www.troublefreepool.com

TriChlor is also much slower acting. CalHypo is the strongest oxidizer we can get over the counter. Fast acting, but doesn't dissolve so fast that it actually reaches the bottom of a pool and land where needed.
There is about 8 ppm calcium in a 1# bag of calhypo. Average fill water in the country calcium is 20 ppm.

 

[Mdragger88]

- Raised FC levels to 3-5ppm by running SWG higher

What fc were you attempting to maintain previously & at what cya?
I suspect it was much too low & that’s why the algae took hold in the first place.

 

[niveknow]

I'm learning more with each passing year on my pool.

I ran my CYA at ~60 from my reading on SWG. At this level, I didn't need to raise it for the SLAM. Assume 15% of that, my target FC is about 9-10? as the appropriate levels!? This ratio is new learning for me and I definitely was not running it anywhere near this number for years. I went with the "book" recommendation at least from my test kits at the 2-3 range for the first couple years. I only raised it to 3-5 this year when the algae was more visible. However when I SLAMed, it went into the high teens which should have taken care of the algae however it didn't budge. Wasn't until this sprinkle method am I seeing it immediately turn brown. Problem now is that I got too exciting thinking I was sprinkling fairy dust all over the my pool zapping away evil. I essentially dropped in 96oz total of 53% trichlor. I don't have a test kit that reads above 10 but some pool math calculator suggest I may be in the high teens. I've clearly overdosed the fairy dust. That's a different problem for me to bring down into safe levels for swimming. However for now the algae is starting to all brown out. So why the high teens SLAM not work, but working now?

 

[Parac]

Your sprinkle method is going much higher than teens in that immediate area for a bit at least. The high teen calculation is only after it has evenly dispersed throughout the pool.

 

[Mdragger88]

Slam level fc for a cya of 60 is 24ppm - not high teens.

Trichlor adds cya - the higher your cya the higher fc you need to be maintaining

Here’s roughly what that amount has done.

I am going to take a wild guess and assume that 53% trichlor has a bunch of additives that you don’t want in your pool aside from cya. Things like copper. Copper causes stains.
It is also very hard to find granular Trichlor in the United States these days - are you sure its not dichlor? If it is dichlor you may have added even more cya.
If dichlor or trichlor is to be used we suggest only using 99% - no additives.
For your experiment I suggest you stick to liquid chlorine in a pump sprayer or cal hypo as suggested above.

 

[Parac]

I don't have a test kit that reads above 10 but some pool math calculator suggest I may be in the high teens.

Lets back up a bit. How are you testing? You can't do a proper SLAM without one of the test kits that has an FAS/DPD test that can test higher levels of chlorine: Test Kits Compared


Also, filling out your signature will help others give the proper advice without having to ask as many questions about your pool setup.
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[niveknow]

Slam level fc for a cya of 60 is 24ppm - not high teens.
View attachment 610363
Trichlor adds cya - the higher your cya the higher fc you need to be maintaining
View attachment 610367
Here’s roughly what that amount has done.
View attachment 610368
I am going to take a wild guess and assume that 53% trichlor has a bunch of additives that you don’t want in your pool aside from cya. Things like copper. Copper causes stains.
It is also very hard to find granular Trichlor in the United States these days - are you sure its not dichlor? If it is dichlor you may have added even more cya.
If dichlor or trichlor is to be used we suggest only using 99% - no additives.
For your experiment I suggest you stick to liquid chlorine in a pump sprayer or cal hypo as suggested above.

I saw that calculator read out as well, but I'm approximating about half that rise given my 53% trichlor. I'm using the Clorox Xtrablue granules in the yellow bucket. Found on Amazon and fine print reads 53% + 'other'. No telling what the other is, but hoping it's not going to be materially negative add to my pool. When I compare it to the Clorox Xtrablue tabs at 95% trichlor that I understand to be typical concentration. That's where my estimation of my current levels came from: 12 ppm from granules + my 3-4 ppm tested FC before sprinkling. Reagent refill coming so I can properly test high range.

 

[cwswifty]

Thoughts on Clorox Xtra Blue products

New guy here. I will be adopting the BBB approach to managing my pool chemistry, but I still have some Clorox Xtra Blue products: Clorox Shock Xtra Blue and Clorox Xtra Blue Chlorinating tablets https://www.cloroxpool.com/products/ The shock has copper, the tablets some form of stabilizer. My...

www.troublefreepool.com

 

[Mdragger88]

xtra blue is no good = copper.

 

[niveknow]

Thoughts on Clorox Xtra Blue products

New guy here. I will be adopting the BBB approach to managing my pool chemistry, but I still have some Clorox Xtra Blue products: Clorox Shock Xtra Blue and Clorox Xtra Blue Chlorinating tablets https://www.cloroxpool.com/products/ The shock has copper, the tablets some form of stabilizer. My...

www.troublefreepool.com

Interesting for sure. Copper? Maybe this helped the algae problem since copper is typically in the algaecide. Not to take away from that perspective, but that was 4 years ago. I wonder if the product has changed since then. I've dumped in 6lbs or the granuates so far and actually bought 6lbs more given the progress. Now folks here are making me think about the copper and what it could mean to my water and equipment. I'm in the saltwater fish hobby and have a high range copper test. I'll test the water after another week or so to see if I'm able to detect copper in the water.

My take away here so far is the sprinkle method seemed to work when I collect the discussion here. Specifically the FC levels especially localized where I sprinkled before the pumps dispersed it throughout the pool. It just works amazingly fast. Maybe the copper in the Blue? Or maybe just combination and cumulative actions over the past several weeks. All I know is I'm not considering all the radical solutions that I've read including draining pool, powerwashing etc. Thanks all.

 

[proavia]

As the copper builds up in the pool water, you will get staining.
Stains are difficult to impossible to remove.
Pretty much every pool product that mentions 'Xtra Blue', blue, blue is going to have copper in it.

SLAM - this includes adjusting CYA and all the other stuff along with SLAM recipe.

What exact test kit do you have?
Test Kits Compared

I ran my CYA at ~60 from my reading on SWG.

The SWG doesn't have a CYA level listed or can it test the CYA level.

Post a full set of current test results from one of the recommended test kits.
FC
CC
pH
TA
CH
CYA
Salt
Water temperature

Pool Care Basics
Overnight Chlorine Loss Test
SLAM Process
PoolMath
FC/CYA Levels

Here's some inspiration
How Clear is TFP Clear?

 

[Mdragger88]

The high local fc level is the secret sauce here - as mentioned this same effect can be accomplished without byproducts you don’t want in the pool by using cal hypo in the same way or liquid chlorine in a $10 pump sprayer.
Definitely no need to drain the pool - black algae requires persistence and patience to overcome while maintaining adequate fc levels. I fear you’re shooting your self in the foot with the blue Trichlor. Possibly Trading one type of stain for another along with making your required slam & maintenance fc levels higher & higher with each application.

 

[SoDel]

It's almost an annual battle and each year I try something new each year with the above tweaks all unsuccessfully.

I don’t know much about black algae but I have a couple suggestions going forward for a pool that is a problem year after year.

One, there might be something going on with your CYA testing and the wrong CYA result will give you a wrong suggested range for your FC. If you run FC at minimums, it can make a difference. The TF Test kits has a 50 ppm CYA reference solution that you can test a get a good feel for what the disappearing dot is “supposed” to look like. It is very inexpensive.

Two, don’t run near the minimums for your particular pool. At a CYA of 60, the pool is “safe” to swim with FC up to the slam level of 24. You might need to experiment to find your sweet spot but I run my pool at CYA around 60 and FC between 7.5 and 10, with a result including not knowing anything about algae lol. The FC chart provides excellent guidelines for most pools but yours might need a little extra umph. The pool doesn’t care about a little extra FC but the algae sure does. Yes, it can shorten the life of the SWG a little bit but the SWG is a consumable and eliminating an annual headache is likely worth slightly shorter SWG life. I have a Hayward T-9 at the end of its 5th season and showing no signs of aging. The extra cost of running FC higher than I “need to” is too small to give much thought to, especially when compared to all the other costs that go with a pool.

 

[Mdragger88]

@SoDel
Maintaining a higher fc level is a one time add to move the bar- be it with liquid chlorine or your swcg.
Daily losses are similar if not the same no matter if you maintain 6 or 10 so the swcg isn’t doing more work really. Going much above that you’ll notice some higher losses like during slam. But If you want the swcg to have to produce less fc daily help it by increasing cya and reducing what is lost to uv. 60ppm cya is a tad low for a swcg pool anytime other than shoulder seasons unless the pool is covered or indoors.