Another CYA and FC Loss thread

[doc8404]

All summer I battled with FC dropping faster than last year and the occasional small patch of algae. Water has been totally clear as always.

since we are getting ready to pull the ladder I wanted to ensure there truly was no algae.

Jacked FC to 19. Morning it is 12.
Pool ia covered with solar cover and pump running.
Jacked up to 18. Morning it is at 11.
I decide to check CYA and it is 20 if I’m lucky. Probably lower.

Is that most most likely what is causing the loss? Zero, not even a trace CC, at any time.

I have 10# of CYA from a source someone posted on here. Before toying with that and adjusting CYA to 40, I wanted to ask.

Thanks.

 

[Dirk]

Don't add CYA just yet (not above 30, anyway), you might have to SLAM your pool. Read about SLAM and see if your pool passes the three tests (The "You are done when:" section). If not, you'll know what to do.

 

[doc8404]

that's my point. I was SLAMing.
sorry i didn't include it.

With such a low CYA, isn't that causing the quick loss?
"
SLAMing an outdoor pool is most effective when CYA is around 30 to 40. Below 30 you lose too much chlorine to sunlight."


I can't imagine algae is eating this when the pool is as clear as it is.

 

[Dirk]

I was leading you to the three criteria, doesn't matter if you were slamming or not. Have you passed the Overnight Chlorine Loss Test?

Yes, it could be the CYA, so bring it up to 30 for your SLAM if you like. But "clear as it is" doesn't mean you don't have algae. Could be hiding (light niche, ladder, skimmer, etc).

Could be a chlorine age issue, could be expired reagent issue (neither likely but possible). First step is to see where you are on the three criteria...

Then post a full set of test results, as those that know more about this than me will likely want to see the whole picture.

 

[doc8404]

As I said. I haven’t passed OCLT.

you say clear doesnt matter. Yet it is one of the three reqs.

The two that matter the most are cya and FC. Both posted.

Ph 7.4
TA 120

CYA 10???
FC as above. Depends when tested.

Chlorine age won’t make it drop faster.
Chlorine age will make it weaker and require more to bring up the FC.

 

[Dirk]

Well, we're certainly miscommunicating, as I didn't see where you said you haven't passed the OCLT.

And I didn't say "clear doesn't matter." What I said, slightly different way: just because the water is clear doesn't mean you don't have algae.

Please read and follow the SLAM directions exactly. Did you do all the prerequisites? When you have passed ALL THREE criteria, then you're done SLAMming. If you can't pass the OCLT, then you're not done.

You must also do the best you can to keep your FC at SLAM level. For a CYA of 20, that would be 10. Raising it above SLAM level will only make it burn off faster, and possibly damage your pool.

So raise your CYA to 30 and maintain an FC level of 12, or if you feel the sun is causing too much burn off, try a CYA level of 40, and maintain an FC level of 16, as per the SLAM directions. Do not let it fall below the SLAM level. Every time you do, you're extending the length of time you must maintain the SLAM.

Reread the Overnight Chlorine Loss Test directions as well, to make sure you are performing that correctly.

I also suggested you look other places for algae, not just in the open water or floor. I meant you should clean those other areas out if you can.

 

[doc8404]

Thanks. Definitely not passing OCLT yet...i just figured it was more related to lack of CYA is all.

Will raise it and keep SLAMing.

I had to SLAM last year and it was one day and done.

 

[Dirk]

I had to SLAM last year and it was one day and done.

Many factors drive the schedule. It can take weeks...

 

[doc8404]

tested. Still low. Back to the sock

 

[domct203]

Thanks. Definitely not passing OCLT yet...i just figured it was more related to lack of CYA is all.

Will raise it and keep SLAMing.

I had to SLAM last year and it was one day and done.

CYA protects chlorine from UV Rays (sunlight). The OCLT takes the UV (& CYA) out of the equation. If you are losing FC when there is no UV (sunlight), then something else is consuming FC, which would only leave organic matter (algae/bacteria).