I've kept CYA at 40 and FC around 7 all summer. In this case I thought FC 7 would be considered on the high side.
Persistent cloudiness and green
- Thread starter rabbet
- Start date
- Jun 24, 2021
- 16,100
- Pool Size
- 29000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
*you've dosed to 7. Then you've experienced daily loss, possibly down to 3 or 4.
At any point in the season, I'd dose so that my low point was still comfortably in target range, preferably the high end. Dosing to 7 is fine when loss is low in the early/late season when you land at 6. But mid season, you want a healthy safety net for any unforseen whoopsies. Some days just have ridiculous UV intensity out of character with the days around it. Or it does so for several days. Or big storms roll through unannounced. Or the Mrs calls you up to say she played hookey and they're having a swim day with some friends.
The charts don't take into account which part of the season you're in, or whatever pops up. That's up to you to be well covered.
For CYA of 40 my minimum FC is 3 and target is 5. So I thought I was doing what you suggest by aiming for 7. Looking back over my log I don't see anything below three except at opening, so I'm a bit mystified. Could circulation of the water be an issue? There is a bit of a dead spot at the deep end at the corner opposite the main drain. That's where I take my water sample, as deep down as my arm and long handled scoop will go. Half the pool, from the inflow at the shallow end to the main drain diagonally opposite at the deep end, gets good circulation, but the other half less so. Also I'm dealing with a ancient pool with square corners and seams, where algae tends to get hold. I have seen algae there while the water is at FC 7.
Low target is 5
And even high target doesn't take into account when you lose 4 ppm a day mid season. Maybe more with a long swim day on a beautiful weekend.
I treat low target as my minimum, and high target is the closest I want to be to my minimum.
Again, it's late season for us and daily loss is falling off a cliff. Targets can be lowered for us going forward. But just a few weeks ago we were in the thick of things. Next season, aim high.
You can test a 7 today but the problem started days/weeks ago when it swung to 3 (or less). Regular FC levels won't overcome an active bloom, so you see it eventhough today is in range.
After all this time I'm beginning to grasp how intricate this is. Right now the pool is clear and chilly. Thanks again for your help.