Any suggestions? I'm beyond perplexed and think I must be doing something wrong..


Jun 6, 2015
Los Angeles, CA
Hi there everyone!

I'm on my 6th day of the SLAM process -(Technically my 15th day , but my first 7 days were wasted because I thought my shock level was supposed to be 16 ug) - but I seem to be getting nowhere.

16.5K pebble pool
Bleach for regular chlorination and shocking
Cartridge filter (Cleaned last sunday)
CYA =50
pH = 7.4 (before shock)
Alk = 90 (before shock)
Hardness = 450
Had a little algae growing that most would not even notice, so it wasn't a swamp or anything to begin with.

Filter running continuously (evenings down to slow speed)
Shocking at 20ppm and testing w NEW dpd powder and new R-0871
Water is clear and pool looks great, actually!
Brushing all areas at least 2 times a day
removed light fixture and cleaned socket as well.

Overnight test results losing 2-2.5ppm at night with 1ppm CC.

Adding 10% bleach throughout the day to maintain shock level.

Today, after this morning's test and adding to bump up to 20, I tested again at 11:00am, had lost about 2ppm (down to 18).
Added bleach once again to get back up to 20.
Waited about two hours, and decided to check again, and level was down to 16ppm. Did the test again to make sure I wasn't losin' it, and still shows 16ppm.
So.,,. within 2 hours, I have lost 4ppm ! This is on day Six of shocking and attempting to maintain 20ppm.

To confirm testing steps:
Add water from 18-20" down in pool water to 10mm in (clean) vial
Add two leveled-off spoons of DPD powder and swirl to mix.
Add R-0871 drops one by one carefully while swirling until pink turns clear. Then divide drops by 2.

Any ideas or suggestions would be great. I have literally added about 20+ gallons of HDX(home depot) chlorine bleach to this pool over the past week or two.) and I'm about to give up and fill this money pit with dirt.. LOL
Thanks in advance!


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
There has to be something in there reacting with the FC to use it up in the dark. And to create the CC. You've scrubbed the lights and the filter. I assume you've cleaned out the pump basket as well. Algae on the backside of the skimmer wouldn't use that much.

Makes we wonder.... could anyone have added any algaecides or stain removers, any chemicals at all beyond bleach and acid? Some of them react and use FC, and some misread as CC.


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
Pool Size
Liquid Chlorine
Did another quick test... My pH shows up as 8.0. :oops: Is it normal to have inaccurate pH readings during SLAM?

Yes. No point testing pH during a SLAM. Ignore pH until the SLAM is complete and you are back at normal chlorine levels.


Gold Supporter
Bronze Supporter
Jun 29, 2016
Tampa, FL
Pool Size
Salt Water Generator
SWG Type
Intex Krystal Clear
John, have you tried testing after addition (let it mix for a few minutes with pump on) to make sure that the FC is getting to 20?

If it isn’t, then you have bleach that isn’t full strength, or you may be misjudging the volume of your pool.


Silver Supporter
Jun 11, 2020
Cincinnati, OH
I have been dealing with a similar problem an I think I was using the wrong pool volume. Initially, I expected the drops in FC as I was SLAMing, but now my water is starting to look great and I still seemed to be losing chlorine too quickly. This morning I finally tried testing, adding chlorine, brushing the pool to mix and testing again. FC was still too low, so I added more chlorine, and gave it more time. Tested again and I finally got my first target reading. My FC was never making it up to the target level in the first place.
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