FC reading different in different parts of the pool

[JessieD]

So I slammed successfully upon opening(took 3 weeks, can't wait for my electric bill!), but now a week later, I've got what I'm assuming is an algae bloom. Lots of dusty dirt reappearing hours after slow vacuuming. So I'm slamming again, but now I'm getting different FC levels depending on where I test. I got a 21 at one end and 18 nearer the middle. I will say, it's an old inground pool, and I think one end has settled a bit lower, so I'm sure the circulation is not what it should be. (If that's even how pool circulation works?!)

Not much I can do about this, just wondering if this is normal or maybe I'm testing wrong? Should I take an average or go with the lowest # when slamming?

 

[Texas Splash]

Yes, that is expected. Pic one spot at the pool for your samples and make it a regular routine.

 

[Bperry]

So I slammed successfully upon opening(took 3 weeks, can't wait for my electric bill!), but now a week later, I've got what I'm assuming is an algae bloom. Lots of dusty dirt reappearing hours after slow vacuuming. So I'm slamming again, but now I'm getting different FC levels depending on where I test. I got a 21 at one end and 18 nearer the middle. I will say, it's an old inground pool, and I think one end has settled a bit lower, so I'm sure the circulation is not what it should be. (If that's even how pool circulation works?!)

Not much I can do about this, just wondering if this is normal or maybe I'm testing wrong? Should I take an average or go with the lowest # when slamming?

Have you done an overnight chlorine loss test to determine if it’s algae or just dust?

 

[Newdude]

Once things are back to normal, consider minimum +3 as your new minimum with that much observed variance. +5 won't hurt either.

 

[JessieD]

Have you done an overnight chlorine loss test to determine if it’s algae or just dust?

Yeah, last night it dropped 3 ppm, but since I noticed the difference in area testing, it made me question everything. I don't live in a dusty or dry area, and this stuff reappears within hours after a thorough vacuum.

 

[Bperry]

Yeah, last night it dropped 3 ppm, but since I noticed the difference in area testing, it made me question everything. I don't live in a dusty or dry area, and this stuff reappears within hours after a thorough vacuum.

If it comes back, it was either never totally dead or the chlorine level is being maintained too low. Will have to figure out which one it is but sounds like maybe the first one. Be super clear you pass all three SLAM exit criteria before you stop. And scrub everything for hidden algae.

 

[duraleigh]

+1 what Bperry said