FC not reading properly?

[JamesW]

Olive green is dark yellowish-green color.

 

[DougFL]

Thanks for replying. Up close it definitely doesn’t look those colors. When I looked at it up close underwater with my goggles on it looked and moved more like dirt or sand. It typically gathers about 4-5 feet from the intake and isn’t always in the shade but seems to gather in the same place every time. It has some characteristics of MA but some characteristics of dirt as well. I feel like it’s safe to assume if what’s in the jar doesn’t grow by tomorrow it’s not mustard algae?

 

[sande005]

Sand doesn't float off. It even sometimes can be hard to suck up in a pool vac, but is easy to push the piles around. I vote for dead algae that used to be suspended in the water when alive, but is being killed by Cl and collecting in areas with reduced current or there is resistance to moving with the flow (like seams). I'm guessing your free Cl is dipping too low at times, and then when you do add more, it kills a bunch of suspended algae...and then perhaps dips too low as a result, so the algae begins to recover.

 

[DougFL]

Thank you for the reply. All of what you’re saying makes sense. I’m new to proper pool care so I’ve been playing catch up for the last 2 months with the TFP method getting everything balanced finally. In May I had negative alkalinity, PH that I couldn’t even get a read on because it was so low, no FC and CYA that I suspect was well into the hundreds. We drained and filled roughly 95% of our pool and our CYA is still around 65 but I find the Taylor CYA test to be very subjective like a lot of people. With my CYA still being high I keep our FC at 8-11 based on the pool math app and recently did a SLAM and met all 3 criteria. My FC was it 21ppm this morning after coming down from the SLAM level and will be more diligent about FC testing now. Hopefully the algae doesn’t make a return.

 

[sande005]

Thank you for the reply. All of what you’re saying makes sense. I’m new to proper pool care so I’ve been playing catch up for the last 2 months with the TFP method getting everything balanced finally. In May I had negative alkalinity, PH that I couldn’t even get a read on because it was so low, no FC and CYA that I suspect was well into the hundreds. We drained and filled roughly 95% of our pool and our CYA is still around 65 but I find the Taylor CYA test to be very subjective like a lot of people. With my CYA still being high I keep our FC at 8-11 based on the pool math app and recently did a SLAM and met all 3 criteria. My FC was it 21ppm this morning after coming down from the SLAM level and will be more diligent about FC testing now. Hopefully the algae doesn’t make a return.

At your level of CYA, I might suggest aiming for 10-11 as much as you can. Then you have a buffer before it drops to 5 or below, for those times you just can't add (stupid life thinking there are other priorities!).
And...you still might see some additional accumulation, even though you passed OCLT. It's dead, but suspended, so may take a bit of time to fully settle out or get captured by the filter.

 

[DougFL]

At your level of CYA, I might suggest aiming for 10-11 as much as you can. Then you have a buffer before it drops to 5 or below, for those times you just can't add (stupid life thinking there are other priorities!).
And...you still might see some additional accumulation, even though you passed OCLT. It's dead, but suspended, so may take a bit of time to fully settle out or get captured by the filter.

Good to know. I think all the dead algae is what had us tripped up because we kept thinking it was live algae and most likely that was mustard algae to boot. The pool looks great today so hopefully with more careful monitoring it’ll stay that way. We’ll be draining and refilling later next month to finally get CYA in check and keep this thing clean once and for all. Thanks for all your help! And go Vikes/Twins/Wild. I’m originally from Minnesota, went to college at SCSU.