SLAMing is not fixing algae in my Spa

[ScienceDancer]

Pool renovation completed July 2022 with Diamond Brite plaster. I have a 20,000 gallon pool/spa combo. Spa had slightly visible green algae only on the wall above the seat. I changed the filtration to Spa ONLY (~ 750 gal capacity spa). CYA @ 30; adjusted Ph to 7.5 and SLAMed to 12 ppm using liquid chlorine. Brushed once per day throughout process.
5/9/2023: Cl 15 ppm.
5/10: 11:00AM - 7 ppm; 1:00PM - 11 ppm; 2:20ppm - 8 ppm; 3:30PM - 13.5 ppm; 5:30PM - 10 ppm.
Changed SLAM target to 16 ppm because when retesting CYA, it might be as high as 40 (so difficult to judge exactly).
5/11: 8:30AM - 8.5 ppm.
5/12: 9:00AM - 12 ppm; decided to drain spa and allow dry and sun to kill algae.
5/13: brushed empty spa and then refilled. Green looks better, but still slightly visible. Changed filtration to Spa and pool as I don't want to create a problem in the main pool! Backwashed DE filter.
5/24: Begin SLAM process again (Target 16 ppm and Ph @ 7.2) with filtration to Spa ONLY @ 11:00AM; 3:00PM - 15 ppm; 8:40PM - 10 ppm.
Each subsequent day, I switched filtration to Pool ONLY for a few hours while the Spa was 'soaking' in SLAM level chlorine, then back to Spa ONLY. Brushed Spa each day.
5/25: 8:30AM - 6 ppm; 10:00AM - 21.5 ppm; 4:30PM - 10 ppm; 6:15PM - 15 ppm.
5/26: 9:00AM - 9.5 ppm; 12:00PM - 17 ppm; 2:30PM - 10.5 ppm; 4:00PM - 15.5 ppm; 6:00PM - 11 ppm; 8:30PM - 14 ppm.
5/27: 8:30AM - 11 ppm; 9:30AM - 22 ppm; 12:00PM - 18.5 ppm; 2:30PM - 14.5 ppm; 3:45PM - 12 ppm.
5/28: 9:00AM - 13.5 ppm; 11:30AM - 17 ppm; 2:00PM - 13 ppm.
5/29: 9:00AM - 5.5 ppm; 11:30AM - 17 ppm; 2:00PM - 15.5 ppm; 6:15PM - 11 ppm; 8:15PM - 14.5 ppm (performed Overnight Free Chlorine Test).
5/30: 7:30AM - 8.5 ppm. Emptied Spa at Noon, again hoping dry and sun will resolve problem. It seems in certain lighting, I can ever so very slightly still see green. It is difficult to accurately visualize, but OFCT really tells me there is still active algae. Water has been, and remains, crystal clear.

I believe I have done a pretty good SLAM procedure, but the chlorine continues to be rapidly consumed. The 'drain spa and let dry/sun kill the algae' was my personal invention -- as I just didn't know what else to do. Spa is still empty.
Anyone have any ideas or suggestions? Greatly appreciated!

 

[Texas Splash]

Welcome to TFP! After looking at your numbers, I see a lot of ups & downs with the FC, but nothing steady or consistent for the proper SLAM FC level which if I understand should be 16 based on your CYA of 40. I also don't see where you passed the Overnight Chlorine Loss Test, so what seems to be happening is you are throwing money into the water without the result. Very frustrating.

The SLAM Process works when followed carefully. So if you confirm the CYA is 40, then do your best (schedule permitting) to maintain the FC level of 16 until you pass all 3 SLAM criteria. Keep in mind that if you see algae growing in the spa, it's probably in the pool as well, so don't overlook ANY part of both areas when inspecting, brushing, etc.

If you have any questions please let us know.

Also be sure to bookmark our Pool Care Basics page for lots of great info. Hope that helps.

 

[ScienceDancer]

I felt certain it was only the Spa where I have an algae problem, but I wanted to confirm. So I performed an OCLT in the pool last night (Spa is still empty) and FC went from 2.5 @ 8:15PM to 2.0 at 7:30 this morning. CC was 0.5 and water is crystal clear.

I can completely sequester the Spa water from the Pool water, with the exception of water contained in the DE filter, which gets mixed together when I change all the valves from one to the other.

Has anyone else tried destroying algae with dry/sun? Do I go ahead and vigorously brush (to remove any algae that has died from dry/sun over the last 3 days) and refill the Spa at this point to begin the SLAM procedure again?

 

[Texas Splash]

With the spa exposed at the moment, go ahead and clean it now by applying a water/chlorine mixture and brushing. Be sure to wear old clothes and eye protection. I wouldn't leave the plaster exposed too long. Fill it back up and definitely increase the FC level in your pool since it was down to about 2 this morning. As a reference take your current CYA level and go to the FC/CYA Levels to see what your normal and SLAM FC levels should be.

 

[Donldson]

Have you ever purged the spa with Ahh-some?

 

[ScienceDancer]

No, though we never had a heater for the spa before the end of last summer when we completed our pool renovation, so it has only been a waterfall feature for the last 31 years. We only got in a few spa sessions before closing the pool for the winter. And given the algae situation, we haven't yet fired up the spa.

 

[ScienceDancer]

SLAM still not working after allowing the spa to remain empty and dry for 3 days. Filtration set to Spa ONLY (~ 750 gal capacity spa). CYA @ 30; adjusted Ph to 7.4 and SLAMed to 16 ppm using liquid chlorine.

6/6: 8:30AM - 0 ppm; 9:30AM - 8 ppm; 10:30AM - 17 ppm; 11:30AM - 15 ppm; 12:30PM - 12 ppm; 1:30PM - 15.5 ppm; 2:30PM - 14 ppm; 3:30PM - 16 ppm; 5:00PM - 11.5 ppm; 6:00PM - 20 ppm; 7:30PM - 17 ppm; brushed spa with algae brush.
6/7: Scum floating so I backwashed DE filter; 9:30AM - 5.5 ppm; 3:00PM - 3 ppm; 6:30PM - 15.5 ppm.
6/8: 7:30AM - 7.5 ppm & brushed; 10:00AM - 21.5 ppm; 3:00PM - 13.5 ppm & brushed; 5:00PM - 13 ppm; 7:30PM - 17 ppm & brushed.
6/9: 7:00AM - 11 ppm & brushed; 10:00AM - 11.5 ppm & brushed; 10:00AM - 11.5 ppm & brushed; 2:30PM - 13.5 ppm & brushed; 5:30PM - 13 ppm; 8:00PM - 15 ppm.
6/10: 7:30AM - 10 ppm; 9:30AM - 21 ppm & brushed; 11:30AM - 17 ppm; 1:30PM - 14 ppm; 4:00PM - 14 ppm; 7:30PM - 16.
6/11: 8:30AM - 11 ppm.

Despite as meticulous of a SLAMing procedure as I can accommodate, I don't seem to be making any progress. For the last 3 days, the end of day chlorine has been pretty much at the target of 16 (since my CYA is 30, that target is actually 11), and the morning reading is about 11 ppm.

Is this the type of stupidity where one continues to repeat the same action, but expects a different result??? What else can I try? A big dose of Algaecide?

Chris

 

[Mdragger88]

SLAM still not working after allowing the spa to remain empty and dry for 3 days. Filtration set to Spa ONLY (~ 750 gal capacity spa). CYA @ 30; adjusted Ph to 7.4 and SLAMed to 16 ppm using liquid chlorine.

6/6: 8:30AM - 0 ppm; 9:30AM - 8 ppm; 10:30AM - 17 ppm; 11:30AM - 15 ppm; 12:30PM - 12 ppm; 1:30PM - 15.5 ppm; 2:30PM - 14 ppm; 3:30PM - 16 ppm; 5:00PM - 11.5 ppm; 6:00PM - 20 ppm; 7:30PM - 17 ppm; brushed spa with algae brush.
6/7: Scum floating so I backwashed DE filter; 9:30AM - 5.5 ppm; 3:00PM - 3 ppm; 6:30PM - 15.5 ppm.
6/8: 7:30AM - 7.5 ppm & brushed; 10:00AM - 21.5 ppm; 3:00PM - 13.5 ppm & brushed; 5:00PM - 13 ppm; 7:30PM - 17 ppm & brushed.
6/9: 7:00AM - 11 ppm & brushed; 10:00AM - 11.5 ppm & brushed; 10:00AM - 11.5 ppm & brushed; 2:30PM - 13.5 ppm & brushed; 5:30PM - 13 ppm; 8:00PM - 15 ppm.
6/10: 7:30AM - 10 ppm; 9:30AM - 21 ppm & brushed; 11:30AM - 17 ppm; 1:30PM - 14 ppm; 4:00PM - 14 ppm; 7:30PM - 16.
6/11: 8:30AM - 11 ppm.

Despite as meticulous of a SLAMing procedure as I can accommodate, I don't seem to be making any progress. For the last 3 days, the end of day chlorine has been pretty much at the target of 16 (since my CYA is 30, that target is actually 11), and the morning reading is about 11 ppm.

Is this the type of stupidity where one continues to repeat the same action, but expects a different result??? What else can I try? A big dose of Algaecide?

Chris

I would slam both pool & spa at the same time. They were mixed at some point so that makes the most sense.
Algeacide won’t fix an algae problem. It is a preventative/ insurance incase of low fc at best.
The answer is the
SLAM Process full stop for both bodies of water.
You are done when:

CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
the water is clear.
(Crystal Clear w/no algae dead or alive)

*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.

 

[ScienceDancer]

Success!! My pool has passed 2 consecutive overnight chlorine loss tests with CC of 0.5 and sparkling water. Thank You!
Chris

 

[Bperry]

Success!! My pool has passed 2 consecutive overnight chlorine loss tests with CC of 0.5 and sparkling water. Thank You!
Chris

Cool. For future reference, the SLAM process usually takes at least a few days up to a few weeks to work. Letting it continue for a couple extra days initially before draining would have been best path forward.