New pool owner, been running SLAM method to try to remove green (algae?) stains.

[ben52]

Hey y'all! New homeowner here in Central Florida. So first, the pool looked fine during the inspection and on closing day. But I neglected the pool for a couple weeks just being overwhelmed with everything and moving in and such. Pool had a leak for one thing so chemicals were being lost fairly quickly. Got that all fixed up but the bottom and sides of the pool are green and have been for weeks. Was doing the pool store thing before I found this place like 10 days ago. So I got the Taylor test kit and the materials needed to balance the pool and start SLAM. I started that on Friday. Pool surface is plaster. There is also an attached spa (not pictured) that actually looks a bit worse than the main pool as well.

Current/most recent levels:
FC = 14.0
pH = 7.6
TA = 140
CH = 300
CYA = 35
SALT = 3000 (I have left the SWG off, my impression is it doesn't need to be on while doing SLAM)

Despite this, I have seen little change on the surface of the pool. When I brush it, a visible cloud of something appears, but it doesn't seem to actually make the stain go away. I have been cleaning the filter as needed (approximately daily). I'll attach a picture from yesterday. I also have picture from around the same time on the previous two days but I see no change between them.

Anyway, any advice is appreciated! I've got a much better grasp of this stuff than I did a couple weeks ago, but still have a lot to learn.

 

[HermanTX]

Welcome to TFP.
I assume your test results are based on your Taylor test kit that you recently purchased.
It it best to round up CYA to the higher decade value i.e. 40 for your test as it is a log scale and not really feasible to estimate the number between 2 marks. Also, have your read the SLAM Process? You need need to bring your FC up to 16 which is 40% of CYA of 40.
You need to test every 3-4 hours and add additional Liquid Chlorine to keep it at 16ppm. This is really important.
Your pH is a little high but do not worry about it now as pH testing with FC greater than 10ppm is not reliable value.
Brush your pool several times a day.
You are correct that you can turn off the SWCG while you are doing your SLAM.
Are you circulating water through the spa as well as the pool? This ensures you have consistent water chemistry in both bodies of water.
What type of filter do you have? Is it a cartridge?
A complete SLAM can take a week plus/minus depending on how well you keep the FC up at SLAM level (16ppm), how much you brush and clean your filter.
Many people have been successful so do not get discouraged. You will be delighted once you see progress and completion.
Since you have a SWCG, you may need to adjust the time it is running or the percentage output to keep your water properly sanitized to prevent reoccurrence. This can be adjusted after the SLAM is completed.

 

[ben52]

Thanks Herman, this is great!

Yes, this is from the Taylor test kit, the K-2006 for salt water pools. Good call on CYA, that makes sense. Yes, water is circulating in the spa as well as the pool. The filter is a cartridge. I will up the brushing to a couple times per day.

Thanks for the info on expected time. I'll keep it up throughout this week!

 

[HermanTX]

Great. Keep us updated.

You may need to clean your filter during the process or definitely at the end, so be prepared for that. Since you have a cartridge filter, some people store an extra filter cartridge so it is an easy swap out to get the circulation back on line. Just monitor your filter pressure. If it goes 25% above the norm then plan to clean. So if at 20psi then it increases to 25psi do the cleaning (or swap out the filter cartridge).

Also, please read the following as this is one of the criteria you need to pass when you see your pool clearing up.
Overnight Chlorine Loss Test. You would do a FC test 30 mins after you add your liquid chlorine (LC) for the evening and then first thing in the morning (before the sun hits the pool & before adding any more LC) to determine your FC loss due to algae. SWCG should be OFF.

Good Luck.

 

[ben52]

So it’s been a week since I started SLAM. There has definitely been improvement, but at this rate it does seem like it could take another week or two... I have been testing and adding bleach as needed 3 to 4 times daily. Brushing, cleaning the filter, and running the cleaner once daily. I’ll keep at it because there is definite improvement at least. I can only really tell because I’ve been taking pictures every other day or so at around the same time.

I actually do have a strange question. Is the only reason to not adjust pH during SLAM because of the phenol red used in these test kits being inaccurate at high chlorine levels? Because I have easy access to a scientific pH probe and so unless there’s another reason I will probably adjust my pH accordingly. If I go this route, what pH should I adjust down to? I Was at 7.6 when I started SLAM.

 

[JamesW]

Looks like copper and iron stains.

Drop a vitamin C tablet on a yellow or green spot.

Can you show the cartridge from the filter?

 

[ben52]

You think so? Yeah I will have to go out and buy some Vitamin C tablets so can't check right away, but I will. I will take a picture of the filter cartridge when I clean it later today as well. Whenever I do clean it, it looks greenish and rinsing it results in green water running off.

 

[HermanTX]

Is the only reason to not adjust pH during SLAM because of the phenol red used in these test kits being inaccurate at high chlorine levels? Because I have easy access to a scientific pH probe and so unless there’s another reason I will probably adjust my pH accordingly. If I go this route, what pH should I adjust down to? I Was at 7.6 when I started SLAM.

You are correct. If you have a pH probe that is insensitive to Chlorine level then you can test for pH.