Black stains just keep getting worse

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Okay, so wanted to give a little update

I’ve done the following
Triple shocked the pool
Brushed twice daily with a stainless steel brush
Placed granular chlorine on the stains twice
Replaced the filter
Put in algaecide

So far the stains are almost all gone. FWIW I did a phosphate test and it didn’t register at all.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
16,030
Northern NJ

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Just used three times the amount of shocked

This is the algaecide I used


What’s weird is I thought I always maintained my water, always thought I kept the chlorine too high so I’m not sure why this stuff showed up


What does that mean?






What algaecide? What ingredients?



Sounds like you had an algae problem. Glad you got it figured out.

Maintain your chemistry following the FC/CYA Chart
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Just a follow up since you guys have been so helpful

I drain the pool enough to expose the sun step.

A pressure washer and even straight acid won’t touch these stains... it’s gotta be a defect in the plaster