Slamming for Algae not Going as Expected

Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
Hi! So I replaced water and brought my CYA down to 50, reduced my pH to 7.2, and brought the chlorine level up to 20. Ran the filter overnight and today noonish the chlorine is a 22, with 0.5 CC. That means nothing is happening, correct? I brushed yesterday, and back washed the day before (although I just realized you need to add back DE after backwashing). Is the lack of DE why nothing is happening? It's yellow algae that doesn't budge when brushing. Could it not actually be algae? I am feeling stuck... any bright ideas?

Pool is 20,000ish gallons, not salt, pebbletec finish. I did previously have high CYA (thanks, pool company). It is high in phosphates, which I know shouldn't matter.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,792
Evans, Georgia
Mandy, first, lets get a signature line going (found under "Settings") so that we know exactly: pool finish, equipment in use, type of filter, how you sanitize the water, any water features, how you test your water (which test kit). This helps us not have to ask questions again and again.. ok?

Can you give us a full set of test results:
FC
CC
pH
TA
CH
CYA
Salt if applicable

What does the algae look like? Is your pool in sun or shade? What chemicals have you or others added to the pool?

Pictures welcome.

Maddie :flower:
 

Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
Mandy, first, lets get a signature line going (found under "Settings") so that we know exactly: pool finish, equipment in use, type of filter, how you sanitize the water, any water features, how you test your water (which test kit). This helps us not have to ask questions again and again.. ok?

Can you give us a full set of test results:
FC - 22 (Leslie's said 16.5)
CC - 0.5
pH - lowered to 7.2 before I started
TA - 110
CH - I don't remember! within range
CYA - 50 per my test (Leslie's said 77)
Salt if applicable

What does the algae look like? Is your pool in sun or shade? What chemicals have you or others added to the pool?

Pictures welcome.

Maddie :flower:
I made a signature! I tried to take a picture, but it's not picking up the yellow way down at the bottom of the pool. I filled in the #s you asked for above. I did add phosphate remover yesterday, as they were over 1,000 per Leslie's test. I'll update after testing today. The algae looks like a true yellow. My pool is in shade more than in sun. We have lots of trees.

Thanks for your help!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Hummm. Not seeing all the test results you mentioned. Only the CYA, pH, FC, and CC. The CH and TA would also be good to know. The fact the yellow doesn't move when brushed tends to seem like it's not algae. The Phos-Free stuff is no issue. In fact, you don't really need to buy that stuff again. It's basically useless. Have you added any other products to the water in the past? Algaecides perhaps? Has the pH dropped any lower than 7.0 that you know of?

Is the yellow all over, or only in certain locations? Can you reach to do some testing maybe?
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,862
SW Indiana
Can you feel the yellow stuff with your hand

The fact that you can’t brush it leads me to think it might be iron staining or iron staining combined with calcium scaling.

A simple test is lay a vitamin C tablet on a yellow area for a few minutes and see if it lightens the spot.
 

Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
Hummm. Not seeing all the test results you mentioned. Only the CYA, pH, FC, and CC. The CH and TA would also be good to know. The fact the yellow doesn't move when brushed tends to seem like it's not algae. The Phos-Free stuff is no issue. In fact, you don't really need to buy that stuff again. It's basically useless. Have you added any other products to the water in the past? Algaecides perhaps? Has the pH dropped any lower than 7.0 that you know of?

Is the yellow all over, or only in certain locations? Can you reach to do some testing maybe?
My filter pressure went way up overnight but still no chlorine loss. Yellow is concentrated in areas, but has spread to a light yellow most places on the bottom. pH per my test this morning was maybe a 7.6. I lowered before I started the slam. TA is 110. I can't remember CH, but it was within range. According to Leslie's, iron is a 0.1, copper is a 0. I will try the vitamin C thing.
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,723
Prosper, TX (DFW)
Any chance you can post pictures?

Also, a couple of questions since your FC seemed to rise the other day:
- Do you have any sort of automatic chlorinator, pucks in the skimmer, or anything else that would add chlorine
- When you say you raised it to FC of 20, did you wait 30 minutes and then test to get that number, or is that what your FC should have been after you added chlorine?

Normally I would say to do an OCLT (overnight test) to see if your chlorine is being used up by something when the sun is not shining to confirm or rule out algae, but lets figure out the questions above first.
 

Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
Any chance you can post pictures?

Also, a couple of questions since your FC seemed to rise the other day:
- Do you have any sort of automatic chlorinator, pucks in the skimmer, or anything else that would add chlorine
- When you say you raised it to FC of 20, did you wait 30 minutes and then test to get that number, or is that what your FC should have been after you added chlorine?

Normally I would say to do an OCLT (overnight test) to see if your chlorine is being used up by something when the sun is not shining to confirm or rule out algae, but lets figure out the questions above first.
I can't get a good picture... looks fine in the picture, not to the eye. No, I do not have a chlorinator, but I also did not retest after adding the amount recommended by the pool calculator. I should have. That said, it was 22 yesterday, and 22 this morning. Zero change. I have vitamin C sitting on a patch now, and so far no change. I'll let it stay for a while longer. Do you think the phosphate remover would cause the jump in my filter pressure? I'm hoping my husband has time for a real clean today. I back washed yesterday.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
If the brushing has no effect, the Vitamin C did nothing, and the elevated chlorine seems to be staying still with no drop, I have a suspicion you may have some calcium scale staining. Calcium scale can sometimes present itself in a dingy yellow color. Are you brushing with a steel brush? Maybe concentrate on one area for a while to see if that helps at all. If any of it was near the waterline, you could even lower the water a little expose it, spray some muriatic acid on it, and watch to see if it fizzes at all. The phosphate remover might have caused a small increase in filter pressure, but at this point with no chlorine loss I wouldn't worry too much about that product. Do you have a chlorine tablet? As a last (organic) test, trying rubbing a puck on the stained for a few minutes. Move it periodically though, don't let it sit in once spot too long.
 

Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
I do have a steel brush, but don't use it as much because it is hard to push. 😬 I will use it today. Vitamin C did nothing. What would cause calcium staining if my CH is only 325? Is there anything to do for that? I can probably get a chlorine puck from a neighbor to try that.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
"IF" it is indeed from scale, it may have slowly developed over several months (or seasons) if the pH got too high couple with warm water temps. Sometimes scale can trap organic material in it as well which can add to the discoloration. But see if the puck does anything. If not, we'll o from there.
 
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Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
I dropped a chlorine puck onto a yellow spot, and low and behold, that spot was perfectly clean when I moved it. Is it possible I don't have enough chlorine?? Leslie's got a higher CYA reading than I did. Maybe they were right.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I dropped a chlorine puck onto a yellow spot, and low and behold, that spot was perfectly clean when I moved it.
Alright! :goodjob: That's promising (organic). Better than heavy calcium scale. So now it's time to review your own FC/CYA, but not with Leslie's or any other source. You still have your TF-100 correct? That's the best way. The CYA test may be tough to do if you have bad weather (cloudy), but if the sun comes out I'd check again. Then do a good FC test as well and let's see where you're at. See my CYA note below.

CYA Testing:
Proper lighting is critical for the CYA test, so you want to test for CYA outside on a bright sunny day. Taylor recommends standing outside with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/gently mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then gently mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. If it helps, pour a little, look away, then look back and pour some more. Some people like to squirt enough solution to go line-by-line for a better feel. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading. If you are still questioning your own results, have a friend or two do the same test 2-3 times. Share your results only after everyone is done to see if you came up with the same average results.
 
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Mandy M.

Bronze Supporter
Aug 6, 2020
12
Houston, TX
Alright! :goodjob: That's promising (organic). Better than heavy calcium scale. So now it's time to review your own FC/CYA, but not with Leslie's or any other source. You still have your TF-100 correct? That's the best way. The CYA test may be tough to do if you have bad weather (cloudy), but if the sun comes out I'd check again. Then do a good FC test as well and let's see where you're at. See my CYA note below.
Hmm. It hasn't been sunny all week. I will do another CYA test as soon as we get sone good light. My chlorine finally dropped overnight! Down to 17.5 FC, 0 CC. I will add more today. Thank you for your help! I am learning in leaps and bounds since I fired my pool company... in hindsight, I should've started pool school first. 😂😂