First time pool SLAM

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
Doing this for the first time, I have read through the instructions, but figured I would post my process in case there is anything I have missed.

--We have noticed very small slimy green spots forming on the bottom of the pool over the last 10 days. Slowly getting bigger, so that as of this morning they are green streaks (this was after brushing the pool less than 12 hours earlier)
--The water is crystal clear
--There have been more stains evident on the liner the normal.
--I also had to bump my SWG up a few notches (its less than 12 months old), so figure something is up.

Test as of last night.
FC: 5.5
CC: 0
PH: 7.5
TA: 60
CYA: 60
SALT: 3200
TEMP: 87

Retested this morning (SWG was on)
FC had dropped to 5.0
No change to the other tests

What I have done:
--Turned off SWG
--Went ahead and added some acid to bump the PH down a notch.
--Removed the pool light from its niche and brushed out any debris
--Added 3 gallons of bleach to bring FC up to 28
--Brushed
--Tested after 30 minutes ( we have great circulation), FC was only 24. Its not uncommon for me to need slightly more chems than calculated, its a custom pool and it slightly bigger than the 12k gallons I was told it was. I also am not sure how fresh the HD bleach is.
--Added more bleach, and will test the levels shortly for baseline.

My next steps are (I think)

--Test every hour (or two later on) and top up cholrine as needed.
--Brush every hour or so
--Once chorline loss stops (via an OCLT) I am done (since the water is already clear and the CC is already 0).

Any other tips?


Thanks so much!
 
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kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
90 mins after starting, FC dropped from 26 to 23.5.
Would that be a good indication that there was some sort of organic issue?

Added chlorine and brushed the seams.
Will check again in an hour.
 

CrystalRiver

Well-known member
Jun 19, 2020
171
Massachusetts
FC loss would be expected to be about 2-4 ppm per day if you didn't have something going on. Losing more than 1.5 in an hour means something's up.

If there isn't something up, you'll pass OCLT tonight, and you'll be done SLAMming very quickly. Based on your numbers, I think you'll have quite a bit of drop overnight.

You don't have to brush hourly. Daily will suffice. Vacuum daily or more often if you see debris. Sneak up on it, or it will poof on you, if it's dead algae. Keep an eye on your filter pressure and backwash/clean whenever it gets 25% higher than clean pressure.
 

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
FC loss would be expected to be about 2-4 ppm per day if you didn't have something going on. Losing more than 1.5 in an hour means something's up.

If there isn't something up, you'll pass OCLT tonight, and you'll be done SLAMming very quickly. Based on your numbers, I think you'll have quite a bit of drop overnight.

You don't have to brush hourly. Daily will suffice. Vacuum daily or more often if you see debris. Sneak up on it, or it will poof on you, if it's dead algae. Keep an eye on your filter pressure and backwash/clean whenever it gets 25% higher than clean pressure.
Thanks Crystal River!!

I am being conservative with my testing as I want to have enough reagent left to test lots once the FC swings reduce.

After the 23.5 reading 1.5 hours ago, I dumped in 70oz of bleach to bring it up to what should be 28.

Just now I retested, and it was down to 25.

Topped it back up based on pool calc and will test again in an hour or so and topup again.

Then do a final test for the overnight baseline once that has had time to circulate.
 

CrystalRiver

Well-known member
Jun 19, 2020
171
Massachusetts
From someone who has been there, done that, go ahead and order your refills now. I've run out twice during my SLAM. It won't happen again.

Once you are done with your SLAM, you can keep good records of before and after test results, and what (how much) chems you add, in order to dial in on your actual volume better.
 

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
I just ordered extra! Good call.

Checked and went to top up, and the FC was at 29. So I'm going to just leave it, and use that for the baseline of the OCLT.

I feel that somewhere along the line, something is out of whack. It may have been the age of the bleach, or the way I do the testing.

I put nearly 5 gallons total of 10% chlorine in, after starting at 5 FC. I know my pool size is a little off for the calcs, but according the PoolMath, the total chlorine added would have increased it by 36 FC, on top of the 5 FC already in there.
Seems unlikely that it burnt up 12 FC in 6 hours.... especially as it was maintaining at 5-6 with my SWG running at 20% up until starting the test.

Probably the HDX bleach.
 

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
Retested at 25.5 FC at 7am this morning. So a significant loss of 3.5 in ~8 hours.

Im going to let it fall further to that we can swim in it today. I think it needs to be under 24 for it to be swim safe with CYA around 60/70.
 

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
I think I may need some help.

I retested the CYA this morning and it is between 50-60. So I have been using 60 for the purposes of calculations.
The target slam FC being 24.

The FC has now dropped from 25.5 to 21 in 5 hours
And I have fresh algae growth.
This area was brushed last evening.
Pump has been running the whole time. In quickclean mode when adding chlorine.

I suspect the answer is, brush, and keep slamming it.

However, I wanted to check whether finding fresh algae development (in an otherwise clear pool), was a red flag while a SLAM was underway?
 

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aeh0603

Well-known member
Apr 6, 2016
351
San Diego, CA
You are correct, the answer is to keep SLAMing. With the rate of chlorine loss you have reported, you still have live algae in the water so keep checking your levels and bringing FC back up to SLAM level at least 3-4 times per day, and brush at least once per day until you pass all 3 criteria to end your SLAM.

1) clear water - for SLAM purposes, this refers both to transparency as well as visible algae. If your water is cloudy or you see algae, you fail this test.
2) CC of 0.5 or less
3) pass OCLT (overnight chlorine loss test)

In the pictures you posted your pool doesn't look that bad, but it could still take a few days to a week or so to pass your SLAM. Just keep at it, the process definitely works! If it takes much longer than that, I recommend posting back here for help troubleshooting why. Good luck!
 

kiwipool

Bronze Supporter
Nov 29, 2018
26
Wilmington, NC
Thanks aeh!

The process was distrupted by the surprise arrival of an inflatable pool slide, then the projected path of TS Isiais....

Im going to restart the process next week. I'm keeping the chlorine highly elevated with the SWG in the meantime. That also gives me time to get more reagents.