Pool growing algae again?

[79TAKid]

about 3 weeks ago I posted about my pool being very green

Pool looks green, sand filter leaking sand into pool


I SLAMed the pool around 6-28/6-29 for quite a few days and it seemed to pass the overnight test. Everything seemed to be good again. Now I believe algae is growing again. There is a 'layer' around the whole pool. Brushing will clean the area but kick up a cloud of brown, just like the last time algae grew. I believe the lowest my FC went was 2.5ppm about 5 days ago. My CYA was still at 40ppm because I never raised it after SLAMing so I adjusted. The pool isn't quite as green as last time (pics in the link above) but it has looked 'off' for a few days and now has that 'layer' of junk. Should I go ahead and SLAM again? Can I do that at 60ppm CYA?

My results:

FC - 7.5
CC - 0
pH - 7.8
TA - 65
CYA - 60
CH - 50


Before brushing


After Brushing same area



Other side of pool after brushing

 

[robertmee]

Yes looks like you need to SLAM again. Unfortunately 2.5 FC was too low with a CYA of 40 and allowed algae to take hold. With a SWG it should never drop below 3 but I'd keep it at least at 5. I keep my SWG FC level at 7 to be safe. You can slam at 60 CYA but you'll need to keep FC at 24 ppm.

 

[Kiss4aFrog]

When possible you want to slam at the lowest CYA level you can, ideal would be 20-30. That way you're using less chlorine to kill the algae.

You can SLAM at 40-60-80 but the higher the CYA the higher the FC level (more chlorine $$) you need to maintain that FC level and to do the same job.

Once you SLAM, the water is clean and you pass your OCLT then you should bring up the CYA level to 70-80 and then maintain the recommended FC level for it from this chart - > Pool School - Chlorine / CYA Chart

 

[kimkats]

It is harder to do a SLAM with your CYA at 60 as it uses more bleach/chlorine. You might want to drain some water to get your CYA down to 30 THEN start your SLAM.

When you did your SLAM did you take your steps out and clean them REAL good? They are an awesome algae hiding place.

Kim

 

[Casey]

When your pool started looking off a few days ago, you should have added a high dose of chlorine that could have killed off the algae before it got the chance to go into a full blown bloom.

SLAM the pool and do an OCLT once it clears.

 

[Defgufman]

My cya is 40 and I dose to 6 fc everyday in the summer. You let it get too low.

 

[Patrick_B]

Indeed, and likely did not complete the SLAM all the way. Or, for sure you didn't maintain good FC if you did, but I'm guessing both. Do anther slam, and make sure it passes 100% without any doubt. If you do this and keep good FC residuals, you will have no more green outbreaks. I promise you, this will be the outcome.

 

[Swampwoman]

Assuming with your salt water generator you adjusted our cya from 40 to 60, did you adjust your ppm of free chlorine to accommodate the higher cya?

Since you're new, I just want to check and make sure you're using the cya:chlorine chart (see link in signature) for your maintenance dosing going forward after the slam. That ratio is the key to trouble free

After the slam this time, be sure to get your cya up to recommended levels and get your output dialed in to the level suggested for swg in the chart.

 

[domct203]

.......... I SLAMed the pool around 6-28/6-29 for quite a few days and it seemed to pass the overnight test. Everything seemed to be good again. Now I believe algae is growing again. There is a 'layer' around the whole pool. Brushing will clean the area but kick up a cloud of brown, just like the last time algae grew. I believe the lowest my FC went was 2.5ppm about 5 days ago.

What do you mean by "seemed to pass"? How long was "quite a few days"? How much bleach did you use?

Letting the FC drop to 2.5ppm most likely let the algae that was still lurking take over again.

SLAM, and be sure to follow the procedure to a "T". If you "guess" you finished the SLAM that is not good enough, you need to be 100% sure you complete the SLAM, even if that means going 1 or 2 days extra.

KILL that Algae, don't dance with it.

Dom

 

[chem geek]

After you SLAM and until you get a handle on setting your SWG system properly, I'd set a higher % ontime for a higher FC target than recommended. Measure the FC at the worst circulation spot in the pool in the morning before the pump and SWG turn on. That's the worst-case situation. Then after you get more comfortable with the adjustments of your system, you can lower the % ontime and FC target to be closer to our minimum FC/CYA recommendations.

If you are unable to consistently maintain at least the minimum FC/CYA levels at all times, then there are other approaches you can take to prevent algae growth but they are extra cost.

 

[79TAKid]

Thanks for all the info. I went right out the night I posted this and started the SLAM process.

It is harder to do a SLAM with your CYA at 60 as it uses more bleach/chlorine. You might want to drain some water to get your CYA down to 30 THEN start your SLAM.

When you did your SLAM did you take your steps out and clean them REAL good? They are an awesome algae hiding place.

Kim

Hi Kim,
I did have enough chlorine on hand (big jug from the pool store) start the SLAM process. By steps I assume you mean the ladder on the side of my pool? I did not take it out last time, I will be sure to do that. Thanks for the tip. I don't believe my regular steps to get into the pool are removable.

Assuming with your salt water generator you adjusted our cya from 40 to 60, did you adjust your ppm of free chlorine to accommodate the higher cya?

Since you're new, I just want to check and make sure you're using the cya:chlorine chart (see link in signature) for your maintenance dosing going forward after the slam. That ratio is the key to trouble free

After the slam this time, be sure to get your cya up to recommended levels and get your output dialed in to the level suggested for swg in the chart.

Thanks, I'll look at the chlorine chart better and keep better track of my ratios. I was trying to keep my FC at 5 but I had problems after I first opened the pool with my SWG until I cleaned it out. It almost seems to me like the SWG's not producing as much chlorine as it used to because I have to run it for more hours. That seems to be the only setting I have on my SWG is how many hours. No time or other adjustments. I set how many hours at night time so it ends up running every night (I run everything 24/7, my electricity bill hates me). I'll read the manual to see if there are any other settings.
SOLVED: SWG making pool very bubbly?

What do you mean by "seemed to pass"? How long was "quite a few days"? How much bleach did you use?

Letting the FC drop to 2.5ppm most likely let the algae that was still lurking take over again.

SLAM, and be sure to follow the procedure to a "T". If you "guess" you finished the SLAM that is not good enough, you need to be 100% sure you complete the SLAM, even if that means going 1 or 2 days extra.

KILL that Algae, don't dance with it.

Dom

Thanks, i've had a lot going on lately and didn't take note of my overnight test so I can't remember my results exactly. I want to say I lost 1 to 1.5 FC over night. Letting the FC drop real low is probably what got me. I had thought since it didn't run out completely I would be okay (now I know better).

After you SLAM and until you get a handle on setting your SWG system properly, I'd set a higher % ontime for a higher FC target than recommended. Measure the FC at the worst circulation spot in the pool in the morning before the pump and SWG turn on. That's the worst-case situation. Then after you get more comfortable with the adjustments of your system, you can lower the % ontime and FC target to be closer to our minimum FC/CYA recommendations.

If you are unable to consistently maintain at least the minimum FC/CYA levels at all times, then there are other approaches you can take to prevent algae growth but they are extra cost.

I'll try to keep it at FC -7ppm & CYA - 70ppm. I let the pool pump run 24/7 and SWG run 6-8 hours (see above)

What should I do if I notice my FC drop low again like when it dropped to 2.5ppm. Do I need to SLAM my pool every time it accidentally gets low? Or just bump my chlorine level up over the Target FC?


Also, no one should swim in the pool while SLAMing, right? I'm not sure if this was mentioned in the Pool School or if it's just common since. I'm in the middle of SLAMing right now and my girlfriend said she wanted to have people over to swim tomorrow. I told her this was a very bad idea because the chlorine level is so high and that no one should swim in it. Was I correct?

 

[domct203]

It's safe to swim if:
You can clearly see the bottom of the pool & when the FC is between min and SLAM level per your CYA.

Dom

 

[kimkats]

If those steps/ladder will not come out get a FIRM bristle brush and use it to clean the underside and back of the ladder. I have a couple of places on my ladder that I have to use a toothbrush to get to BUT I know this and do it.

Kim

 

[chem geek]

What should I do if I notice my FC drop low again like when it dropped to 2.5ppm. Do I need to SLAM my pool every time it accidentally gets low? Or just bump my chlorine level up over the Target FC?

It depends on how quickly you catch the drop. If it's caught early then a full SLAM may not be needed and you would just elevate the chlorine level. Is the issue that you have varying weather so if you set your % ontime to handle partly cloudy days then a bright sunny day is consuming too much chlorine? Just because you have an SWG doesn't mean you can "set it and forget it". Regular testing is still needed and adjustments made either by supplemental manual dosing or by adjusting the % ontime as needed.