FC at 0.0

Naplespool

Well-known member
Mar 26, 2017
81
Naples/FL
Plaster pool, SWG.

On Friday morning,

FC 6.0
PH 7.6
TA 60
CH 325
CYA 50
Temp 81

Sat AM noticed slight haze. Sat PM more Haze. FC 0.0 Nothing like this has ever happened.

What could have happened? (I am Slamming Pool now.)
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
12,432
Evans, Georgia
How cold is your water? As water cools your SWG doesn't work under a certain temp and you may not have realized that.... it allowed your FC to disappear since it wasn't being produced.

That let algae take hold of your water. Hence the need to do that SLAM process the water.

Maddie :flower:
 

Naplespool

Well-known member
Mar 26, 2017
81
Naples/FL
Thanks for the responses. Pool temp was 81-82. SWG is working.

The astounding thing is that Friday morning I had 6 ppm FC but by Saturday afternoon FC was 0.0. FC has been at or above 6 for months, CYA was 80 but had drifted down due to rain, to 50.

The SWG has only had to produce 1.3 ppm FC per day (32% times 22.4 oz/day times 10/24 hours) to maintain 6 ppm FC.

And then boom, I get hit with an algae bloom. The only thing I can think of is that we had a few days of showers recently ... ??

SLAM has been above 20 ppm FC for three days, pH reduced to 7.2 before the SLAM, and last night’s chlorine loss was less than 0.5 ppm. No CC.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
SLAM has been above 20 ppm FC for three days, pH reduced to 7.2 before the SLAM, and last night’s chlorine loss was less than 0.5 ppm. No CC.
Very good. Stick with it until you pass all 3 criteria. Make sure to look all around the pool for any potential hiding spots where algae can grow. Maybe behind a light or something? The rain itself shouldn't be a factor, but perhaps the rain picked-up and deposited some unusually heavy particulate in the air? The falling CYA "might" have resulted in less SWG efficiency and FC retention - maybe. Your water is not too warm, so that may be a stretch. Either way, knock it out now and start the new year on the right foot.