Is SLAM inevitable? (YES...it was...5 Days of stress complete now)

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
Just had my first FC mishap where it dropped below expected and dipped below the minimum.

Pool crystal clear entire time...but FC wouldn't rise.

Here are my log notes
PH is 7.5
CYA was increased from 60 to 80 during these notes


Date FC
5/4 7.5
*Turned SWG off to check drift
5/6 5
Similar testing from 5/7 to 5/13 trying to dial in my SWG...jumping ahead to real issue

5/13 4
*Turned SWG back on to try and dial it in
5/14 5.5
5/15 *Added 2.5lbs CYA to reach target of 80
5/16 7
*Weekly skimmer check and cleaning
*Turned SWG off to drift down to 4 again for further dialing of SWG for swim season.
*Was expecting 1-1.5 loss per day based on past week of testing
5/19 1 (5pm)
*Was expecting it to be 4ish when I checked...was surprised it was this low. Cranked my SWG back on and up to 100 and let it run overnight (in hindsight i should have used liquid chlorine for instant increase)
5/20 4.5 (6am)
*In the morning my FC was about what I expected...however it never went above this number in subsequent days
5/21 4
5/22 3 (6am)
*This was a red flag b/c I ran my SWG overnight again to try and get numbers up and over 4.
*I added 2 jugs of 10% home depot chlorine to confirm it would raise as expected and observe how much FC I lose.
*I wanted to get FC up and above the minimum and observe how much I lose with SWG turned off
5/22 15 (10am)
*2 hours after adding chlorine the FC is where I expected. My SWG is OFF so any change is purely due to sun + organics in the water

As prep for increasing my FC with liquid chlorine I was scrubbing and cleaning up all leaves etc. in the pool so nothing I could control interfered with FC tests
During my thorough clean and brushing of the pool on 5/22 before I dumped in the chlorine I discovered a dead bird in one of my skimmers that was partially decomposed

I'm hoping this bird carcass is the cause of my mystery FC loss and it died on 5/20 or 5/21 causing the unexpected changes to FC

If not I will be continuing on to my first SLAM ever

For now I am in observation mode

Any tips/advice to guide me are appreciated
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I would definitely increase the FC to SLAM level - should be 31 if your CYA is 80. Maintain that FC of 31 today and inspect everything. Brush all areas of the pool and then do an Overnight Chlorine Loss Test this evening. Make sure the SWG is off when you begin the OCLT. That should be a good indicator as to whether or not your water is able to hold FC well. If you fail the OCLT, continue with the SLAM until a 3 criteria are good. Best of luck!
 
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NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
I would definitely increase the FC to SLAM level - should be 31 if your CYA is 80. Maintain that FC of 31 today and inspect everything. Brush all areas of the pool and then do an Overnight Chlorine Loss Test this evening. Make sure the SWG is off when you begin the OCLT. That should be a good indicator as to whether or not your water is able to hold FC well. If you fail the OCLT, continue with the SLAM until a 3 criteria are good. Best of luck!
That is what I was afraid of

I guess the follow up question is what is the "safe" FC upper limit to use the pool again?


I remember reading 10 or less especially with children who inevitably swallow water.

After I pass all 3 criteria I need to let FC drop normally.

My normal FC drop is 1-2 per day. Am I out of commission for 2 weeks after SLAM is over?
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
I have a huge sad face right now...thought I was doing well.

SLAM #1 feels like I failed.

This was a very important lesson for me that "clear" doesn't mean ok

I have the robot doing a last minute cleaning then I will bump FC up to 31 and manually brush everything
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
SLAM #1 feels like I failed.
Don't be so hard on yourself. The good thing about this SLAM is that you caught it early while the water is clear. Hopefully you'll rebound back quickly. That's one advantage of being in control of your water as opposed to blindly taking someone else's word for it. And remember, you can still enjoy the water with an FC up to 31. Take the time while in the water to do some housekeeping and brush everything. Hopefully you'll get past this SLAM soon.
 
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NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
Think I figured out the puzzle

My FC has only dropped from 15 (10am) to 14 (3pm).

Was confirming how much more liquid chlorine was needed to hit SLAM of 31

However when I went to check on the pool cover I noticed it has a slimy feel and odd smell on the bottom.

I am guessing when my FC dropped algae growth started on the cover.

Once I pulled the cover off this morning it removed the huge demand for chlorine and my FC boost was easily enough for the clear pool without cover contamination

Once I confirm pool is ok with OCLT I will clean the cover with a diluted mix of chlorine before even considering placing it back in the water.

Weather is supposed to reach triple digits next week. May not put the cover back on for a while.

Fingers crossed!
 
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NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
CYA = 80
SLAM target = 31

6pm check I only had FC of 24

Either I didn't get up to my target of 31 with my 3pm addition of 3 gallons or something used it up in the 3 hours that passed

Brushed the entire pool

Afterwards I added 1.5 more gallons (pool math suggested 1.25 gallons but I wanted to be on the conservative side)


Next check is after dark
 
Last edited:

Newdude

Well-known member
Jun 16, 2019
2,443
NY
Is every hiding spot cleaned and drained ? Ladders, water features, lights, etc ? The standard pipe ladders can hold several gallons of old water.
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
Is every hiding spot cleaned and drained ? Ladders, water features, lights, etc ? The standard pipe ladders can hold several gallons of old water.
I did NOT run my water feature....turning them on now (920pm)

Have weeping walls and grotto

Just added another gallon of chlorine

Was at 28.5 instead of 31 as expected

Will do my OCLT reading after 10pm then again at 530am
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
Day 2 SLAM recap
CYA 80 (Target 31)

5/22 30.5 1030pm OCLT baseline (.5 CC)
5/23 24.5 530am OCLT check (.5 CC)
*OCLT#1 failed
5/23 26 1130am (0 CC)
*Ran all water features for 30 min
*Gave pool another thorough brushing
*Also removed the caps from my umbrella sleeves and exposed everything to water
5/23 34 1pm
*Overshot my target of 31. Maybe the 0 CC result finally indicates I killed off the organics and am back to stable

Will check again in the evening and prepare for OCLT#2
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
I know I should trust the numbers but I am feeling extremely discouraged right now.

Checked at 6pm and my FC had dropped from 31 all the way to 26 in 5 hours

CC was at 0.5 yesterday but has been steady at 0 today

I know such a big loss can't be solely due to sunlight...and I can't find anything in the pool when I am cleaning.

Every time I check it seems I have dropped from my SLAM target to the 24-26 range.

What hidden organic could keep draining such high amounts of FC and surviving this long?

Uggg...

patience patience patience
 

Newdude

Well-known member
Jun 16, 2019
2,443
NY
I dunno what keeps messing you up, but whenever you get discouraged for a moment, ask yourself if you'd rather have the pre battle or the post battle. Its not fun right now, and its been mind boggling fustrating at times, but you are still on the offense. You are beating it down before it happens. Once it happens..... it will be far worse playing defense.

Would an ammonia battle leave you with clear water but major FC loss ?
 
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zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,240
Houston, Texas
Check to make sure you are hitting your target FC. Test FC, add enough according to poolmath to hit target FC and let it circulate for 15 minutes then test FC again. You should be very close to your target. If FC is lower than expected, check the age of your liquid chlorine. There should be a julian date on the bottle that tells how long ago it was made. The older the chlorine, the less potent it is. Also, try to remember where the chlorine was kept when you bought it. Chlorine stored outside will age quicker than chlorine stored in a dark, cool area.
Another thing to check is that you are entering the proper strength of chlorine in poolmath. Make sure you are not calculating values based on 10% chlorine when you use 6% bleach.
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
If my pool were green or cloudy it would be easier for me to be patient

Pool is literally crystal clear right now

The logic side of me is saying be patient and follow it through to the end. But a part of me is screaming what the heck is going on because I dont understand such huge FC losses in a clear pool with CC of 0
 

NorCalX

Gold Supporter
Feb 3, 2011
297
Brentwood, CA
Check to make sure you are hitting your target FC. Test FC, add enough according to poolmath to hit target FC and let it circulate for 15 minutes then test FC again. You should be very close to your target. If FC is lower than expected, check the age of your liquid chlorine. There should be a julian date on the bottle that tells how long ago it was made. The older the chlorine, the less potent it is. Also, try to remember where the chlorine was kept when you bought it. Chlorine stored outside will age quicker than chlorine stored in a dark, cool area.
Another thing to check is that you are entering the proper strength of chlorine in poolmath. Make sure you are not calculating values based on 10% chlorine when you use 6% bleach.
I have been overshooting my target to be on the safe side.

The red flag of concern is when I test again 4 to 5 hours later and see the huge drop

Definitely have a mix of potent and old 10% liquid chlorine from HD. Saw dates ranging from October 2019 to march 2020

The dates are printed on the box so I can see when I open them up.
 

Newdude

Well-known member
Jun 16, 2019
2,443
NY
Yeah but you are testing after you add them so the strength is accounted for if you reached your 30 target. If you just dumped in weak jugs, and were lower than you expected hours later, then that could be.
 
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