maybe I got too confident

[Bessemer]

We are in our third season with our pool (in-ground, 15000 gallons, vinyl liner). I have told everyone who asked that keeping a pool crystal clear was not that hard as long as you kept up with testing, and up to now we've never had a problem. But the water temperature went from low 80s to upper 80s and we got a tiny bit of algae. Not much, but enough to notice. I had gotten lazy at checking chlorine levels, just letting the SWG do its thing. Chlorine dropped to 2-3 ppm when the algae started. I set the SWG to super chlorinate and got chlorine up to 5+ and I added some algicide. Now there is no hint of green, but for days now the water has been cloudy-gray. I've been running the sand filter 24 hours a day for the last two days with no obvious effect. Current readings:
FC - 5.5
CC - 0
CYA - 60 (although it could be 50 to 70 - I have a hard time reading that test)
total alkalinity 90
calcium hardness - 125

I am stumped, although maybe the sand in our filter needs replacement. I don't know how old it is, since it was here when we bought the house. I bought some stuff called Sparkle Filter Aid that is supposed to increase the efficiency of the sand filter. It might have MAYBE helped clear the water a tiny bit, but I had to backwash after a couple of hours since the pressure went up.

Thoughts and suggestions would be very much appreciated.

 

[JJ_Tex]

There are lots of red flags in your post pointing to algae, not a filter issue.

Do an OCLT tonight, with the SWCG off and see if you pass. If you fail, start the SLAM process.

 

[Bessemer]

thank you JJ-Tex.

Will do the overnight test and will report back, but for my education - what is it that suggests algae is the issue? Looking at the water and the pool surfaces I don't see anything green (or black or yellow). What should I be looking for?

 

[JJ_Tex]

thank you JJ-Tex.

Will do the overnight test and will report back, but for my education - what is it that suggests algae is the issue? Looking at the water and the pool surfaces I don't see anything green (or black or yellow). What should I be looking for?

Here were the red flags I mentioned. Keep in mind that you don't always have to see algae for it to be present, it lives in the water way before it meets up with enough friends to start growing in spots on the wall for you to see.

and we got a tiny bit of algae. Not much, but enough to notice. I had gotten lazy at checking chlorine levels, just letting the SWG do its thing. Chlorine dropped to 2-3 ppm when the algae started.

Since you didn't do a proper SLAM, there is a good chance you have algae in the water even if you cannot see it.

Now there is no hint of green, but for days now the water has been cloudy-gray. I've been running the sand filter 24 hours a day for the last two days with no obvious effect.

Most of the time, cloudy water is algae. Unless you have a flood or some other mud/dust-like contaminants, its almost always algae. Algae lives in the water well before it starts forming on walls where you can see it as algae.

It might have MAYBE helped clear the water a tiny bit, but I had to backwash after a couple of hours since the pressure went up.

A quickly clogging filter is collecting something, likely algae. Note, there is a common misconception that your filter kills alage. A filter does just that, filter particles out of the water. It could be dirt, dust, alive algae, dead algae, your filter doesn't care. Also the algae doesn't care either. It will gladly live inside the filter as it would suspended in the water or on the walls. Chlorine is what kills algae.

 

[Bperry]

thank you JJ-Tex.

Will do the overnight test and will report back, but for my education - what is it that suggests algae is the issue? Looking at the water and the pool surfaces I don't see anything green (or black or yellow). What should I be looking for?

The algecide would also be a red flag. Good ones can sometimes belp prevent algae but not so good products can cause problems like that and dont do well with algae thats already there. Dont use anymore of that stuff as its not needed.

 

[Bessemer]

Free chlorine at 9:30 last night was 5.0 (SWCG had been off for about four hours at that time)
Free chlorine this morning at 7:00 was 4.5 (SWCG off all night)