Reason for never-ending algae: pool light?

MLock

Well-known member
Jul 5, 2011
63
0
Indianapolis
#1
My water is clear, but I lose about 2.5-3ppm of FC overnight each night, and I'm adding more bleach than I (think I) should have to.

I'm generally trying to hold at around FC6 (CYA45), but after a long hot day (it's been over 100 here recently), I can find myself down to 1.5 or 2. At that point, like I've said in another thread, my vinyl seams darken and it appears I'm fighting algae again.

My pool light was black when I opened earlier this year, but cleared up when the pool did -- after about 55 gallons of 10%. :eek: However, now, if my pool gets down to the 1.5FC level, that light starts to blacken right back up. Obviously there's no circulation in or behind the light.

So, I loosen the light and pull it free; black particulate is flying everywhere, the light housing is rusted and there are holes and water in it (but amazingly, the bulb still works), and the niche (I think that's what it's called) is just covered in black stuff.

Obviously, replace the light and clean the niche, right? I'm on my fifth paragraph and now getting to my question: how do you do that? I can't lower my water far enough (12" remaining in the shallow end is about 3" above my light) without floating the liner -- do I just use a toilet brush and let the crud go its merry way in the pool water and then rock some "shock+" levels for a while? How do I get the algae that is invariably back in the conduit to the electrical box?

I want this stuff gone!
 

woodyp

Mod Squad
LifeTime Supporter
TFP Expert
Apr 18, 2010
10,206
0
East Texas
#2
With CYA of 45-your minimum FC should be 4. Your taget is 3 to 4 points higher than that. Just means you should expect to lose 2 to 3ish of FC per day under NORMAL circumstances. You definitely need to shock with that overnight loss.
 

JasonLion

LifeTime Supporter
Platinum Supporter
TFP Expert
May 7, 2007
37,879
5
Silver Spring, MD
#3
Removing the light fixture for a day while shocking, combined with a little brushing in the niche should take care of it. That will put some debris into the pool, which you will need to vacuum up.
 

MLock

Well-known member
Jul 5, 2011
63
0
Indianapolis
#4
Thanks Jason. I haven't been able to find "best practices" on here regarding light/niche maintenance. Should they be removed frequently to avoid this?
 

chem geek

LifeTime Supporter
TFP Expert
Mar 28, 2007
12,082
2
San Rafael, CA USA
#5
If you clean it thoroughly enough and maintain chlorine levels, it shouldn't come back. However, we haven't had enough experience of people cleaning behind light niches to know for sure. Those that do so to get rid of yellow/mustard algae don't seem to get the problem again, but you've got something different with that black stuff.
 
Jul 4, 2013
1
0
#6
This is my exact problem and it is driving me CRAZY! Were your measures successful? Is there a way to rectify this situation without removing the lights? Pool store says they never heard of this problem before and seem like they don't believe me, telling me I should take pictures. The metal ring gets covered in something, too. It doesn't appear too well in pictures.