Brown patches on bottom of pool...


New member
Jun 8, 2021
new here...but i have been using the tfp method since july of last year...this year i added an swg to my 12500 gallon above ground pool which i havent used yet...after opening, i slammed the pool...and then added salt and raised the cya to swg levels...i noticed the brown patches the bottom and did another slam which was difficult due to the high cya of 70...testing was difficult with a fc level of 33... but i did successfully pass the slam i let the fc drift down to 22 and tested overnight fc loss and no cc...but i did see a few new brown i am assuming the patches are dirt....also found a gritty brown sand in the robo from here on out i intend to do the overnight test and check for fc loss before i slam...i use bags of shock to raise the fc rapidly and i am suspecting that a some of the powder i am seeing at the bottom of the pool is the "other ingredients" in the pool shock or dirt from the environment

so i guess my question the overnight fc loss test valid at all times or only after a slam...i would hope its valid at all times...if so i wont panic until i actually get testing numbers to validate an algae problem

hi to all and thanks for sharing...i have learned so much here...

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
Texas, San Antonio/Marion, South-Central Area
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
Welcome to TFP! :wave: The Overnight Chlorine Loss Test is valid and can be performed at any time. It is not SLAM exclusive.

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New member
Jun 8, 2021
thanks for responding...from here on out i will regularly check with the oclt before going crazy and spending money on an unnecessary gets expensive with the high cya and the amount of 871 drops used..thanks again i appreciate it!
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Silver Supporter
In The Industry
Aug 15, 2017
Spring Valley, NY
But wait a minute, you said you passed OCLT but in essence you have not since it includes 3 criteria which one of them is visual. They may not be algae and in that case your good but further inspection ought to figure it out. Does it move with the brush and create a puff of a cloud or is it like moving sand which won't create a cloud and disappear. And so you know you can do the FC test using 5 ml and each drop =1 untill you get closer to the end of slam.