Dirt or Algae in Phoenix?


Jul 26, 2020
I have a 10k pebble tec pool with a 1.5 single speed pump and sand filter. I have the Taylor kit. I don’t always run all the tests.
This has been happening for a while when I brush the pool I will see brown stuff that clouds the pool (usually after it’s been very windy) and then the pool will be fine when the weather is calm. I’ve raised the FC to slam levels a few times and have kept it fairly high. So I’m inclined to believe that it is dirt not algae. Anyway I’m open to what you think.

This is what happened this past week:

Saturday: I brush the pool walls and there’s minimal dirt. FC 6; CC 0; PH 7.5; CYA 60 CH 450 TA 60
I decide to start slamming and add 10% bleach
Sunday (lots of wind overnight and there’s a lot of little debris in the skimmer basket- when I reach into clean it my arm is covered in small particles). Initially FC 19 Ph 8
I add more bleach and MA
FC 24 ph 7.4

Monday: brush and there’s hardly anything on the stairs and walls. FC 24 ph 7.4

Tues and Wed morning same as Monday minimum dirt and debris seen when brushing FC 24 ph 7.4 Weather calm

Wednesday day and night very windy. I skim the pool a few times throughout the day and before bed.

Thu (today) the pool had a lot of debris and leaves in the morning (filter set to start at 9am). I skimmed and brushed the walls. There was a lot of brown stuff that made the water cloudy when I brush the walls. It did puff up and form a cloud towards the bottom of the pool and kind of hang there for a bit. FC 21.5 ph 7.4. Out of precaution I added bleach to raise FC to 24.
I noticed the vacuum didn’t get all the brown stuff and it’s obvious where the vacuum missed. The water is clear (not murky).

So is this algae or dirt?


Silver Supporter
In The Industry
Aug 15, 2017
Spring Valley, NY
Well to begin FC of 6 is borderline at CYA 60 and my very well have algae. You started slam but have not followed the slam process. Read how to slam and you'll know you're done after a OCLT when met with all 3 criteria.


Jul 26, 2020
I followed SLAM. Lowered ph, raised FC and ran filter. There was nothing brown after 24 hours. Directions say you can stop when the water is clear, FC is maintained and cc is zero. I didn’t run the filter continuously after Monday because there was no need for it.

The FC of 24 was maintained for *3 days in a row* (so no overnight loss) This is not uncommon for winter when I get 1-3ppm/week of FC loss.

It is strange that after *3 days of FC of 24 (no loss;0cc) and no brown stuff* then there is a very windy day there debris and brown stuff (algae or dirt) on the walls.

Like I have said I’ve done this very same process before with similar results. The brown stuff seems to appear when it’s windy or when the landscaper comes.


Gold Supporter
TFP Guide
Jun 16, 2019
If you pass the Overnight Chlorine Loss Test (which you did) then you are good. Usually it’s all over everything..... your car, the deck, etc. but if it’s super windy it will blow off all that stuff and not be evident. Whatever blows into the pool mixes and stays there.

Also just making sure your sig is up to date and there is no SWG. That will help you pass the OCLT and give more headaches when you think there is no problem but there is.
Thread Status
Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.