Here We Go Again - Perfect Chemical Balance + Algae

[Seadweller]

Well, the story repeats itself. I returned from a 5 day vacation to find algae in the pool. I immediately thought the chlorine must be low. To my surprise, here are the readings using my test kit:

FC 12
CC 0
PH 7.5
TA 90
CH 400
CYA 70
NA 3800
CSI -.11

I even put half a bottle of algaecide in the pool before I left. My son checked the pool on Wednesday, and all was fine. Folks at the pool store said they've had a record number of algae complaints. Has the algae become resitant to chlorine? How on earth can I have algae? I solved my circulation issue 2 years ago. It's now Dang near a whirlpool. What on earth could be the cause??

Alien strain of algae perhaps?

 

[HermanTX]

Well your test numbers look great and it appears you had your SWCG on the whole time you were away.
Could the "algae" be just pollen or something similar that you are mistaken for algae? Was it a localized area or throughout the pool?

 

[summertimesadness]

I have been finding, that what was algae, was actually dirt / sand. Even if I brushed it, it would just resettle in other areas. I ended up diving into the deep end where I noticed some gathering and it was fairly gritty.

I run the pool robot every few days, and it cleans it all up. The filter basket is littered with dirt and sand.

 

[RLP]

Do an overnight chlorine loss test.

 

[Seadweller]

Thanks guys...It's on the walls around the entire pool, more near the pool floor in some areas. It's absolutely green algae. I'll do an overnight loss test, but I can't see any possible way it would drop from an FC of 12, to a level low enough to cause algae growth. My pool cleaner runs 18 hrs./day with the pump. Completely stumped.

 

[JamesW]

Algae happens when the FC is too low.

Maybe your test results are off?

You should review your test procedures.

You also need to brush periodically.

 

[Seadweller]

I tested the water this morning, and the FC is still at 12. It actually sounds like I need to back off on the salt system run-time a bit. It's running for around 16 hours/day at 100%. The pump/filter is running 18 hours/day. I can't imagine I'm not getting enough turn-over. You'd think an FC of 12 alone would prevent algae, but what boggles me, is that I put a bottle of algaecide in the pool before we left last Sunday. By this past Friday, or even earlier perhaps, algae appeared. I didn't have time to brush the pool since we've returned, but did so this morning. There was more algae this morning than there was on Friday, so it's proliferating somehow.

If FC and the other chemical levels are OK, turn-over is OK and circulation is OK, and I took the extra step of adding algaecide, what's the missing link?

Certainly a mystery.

 

[JamesW]

In my opinion, algae does not lie.

The algae is telling you that it is not bothered by your level of chlorine.

If you have algae, the FC is insufficient.

 

[mrm1682]

I was in a similar spot last fall and I never found the cause and gave up since we were closing the pool for the winter. I did a deep clean of the sand filter this spring and have had a clean pool until recently when I think I just got behind on adjustments for the hotter weather coming in. Is your filter ok?

 

[duraleigh]

I want to bolster what JamesW is saying. Algae and adequate FC are simply incompatible.

Chlorine kills algae. If you have algae in your pool your chlorine is inadequate. Perhaps there is not enough mechanical action (brushing, vacuuming) to expose the algae to the chlorine.

Algae can often form biofilms that shield the algae from the chlorine. That's why brushing, vacuuuming, filtering are all essential parts of pool water maintenance.

Additionally, there has not yet been discovered any "magic" algae that can overcome this science and make the outcome different. Chlorine kills algae.

 

[Mdragger88]

While your fc numbers are certainly good now they must have been too low at some point. Maybe during your vacation or even before? Without seeing all your logs it’s hard to know exactly when the problem began. A swcg can sort of mask a problem/ keep it at bay for a little while but algae eventually wins.
At any rate you must do the
SLAM Process & be absolutely certain you have been thorough & passed all 3 end of slam criteria before stopping.
Be sure to do all the things:
*Check & scrub every nook & cranny where algae may hide (light niches, steps, drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.

 

[PieterS]

That's why brushing, vacuuuming, filtering are all essential parts of pool water maintenance.

I find this to be key - especially when away from the pool for a week plus. Even though FC is maintained by my SWCG and doesnt appear to drop below minimum, if the pool is not disturbed at all (no swimming/brushing), algae will still take hold.

 

[Seadweller]

Thanks gang....If an FC of 12 isn't sufficient, how high must the FC be in my case? Before I left on vacation, I made sure FC was good (10 at the time). I don't see how it could have dropped to a level that would promote algae growth, and then return to a level of 12 by the time I returned 5 days later. CC's read 0, so I assume that doesn't mean there's no algae present?

Will brushing that algae into the chlorinated water kill it (addressing the bio film), or do I need to SLAM the pool?

 

[duraleigh]

Will brushing that algae into the chlorinated water kill it (addressing the bio film), or do I need to SLAM the pool?

You need to do both! Since it's there and you can see it brush it up into the chlorinated water first and then SLAM the pool. Don't take shortcuts with the SLAM. Each word in that article has been put in there to insure success. Don't deviate.

 

[Mdragger88]

Thanks gang....If an FC of 12 isn't sufficient, how high must the FC be in my case? Before I left on vacation, I made sure FC was good (10 at the time). I don't see how it could have dropped to a level that would promote algae growth, and then return to a level of 12 by the time I returned 5 days later.

My bet is that a dip happened sometime before then - logs would be key to figuring this out.

CC's read 0, so I assume that doesn't mean there's no algae present?

No- while the presence of elevated cc’s indicates a problem the absence of cc’s doesn’t mean there isn’t one. You have visible algae- there’s a problem.

Will brushing that algae into the chlorinated water kill it (addressing the bio film), or do I need to SLAM the pool?

When it’s basically invisible (very low level) maybe
What you described

It's on the walls around the entire pool, more near the pool floor in some areas. It's absolutely green algae.

requires the
SLAM Process.
You don’t need to do an oclt - the visible algae is your indicator to slam.

 

[RLP]

Is it possible there was a power failure?

Happened to a friend of mine, went on vacation and came home to a spoiled food and a disgusting refrigerator. Found out the next day the power was out for a couple of days.

 

[Mdragger88]

Is it possible there was a power failure?

Happened to a friend of mine, went on vacation and came home to a spoiled food and a disgusting refrigerator. Found out the next day the power was out for a couple of days.

I was just talking about this regarding my freezer (I think it has been intermittently thawing some) I have noticed some food that is quite frozen now but seems to have been thawed at some point since it was placed in the freezer.
The op’s swcg could have “made up” the difference & been back in range upon return if the power failure happened early on in the vacation.

 

[Seadweller]

Thanks for the input/advice gang. I suppose it's possible the power went out, but the pool was checked on Wednesday and there was no algae present, so this occurred between Wednesday afternoon and Friday evening. I don't recall the FC level ever dropping below 6, but I guess it's possible it could have dipped and caused the algae to grow. Looks like it's time to SLAM.

 

[Mdragger88]

Quick question- do you have a cover? If so was it in use?

 

[mkolb]

Are you sure that your CYA isn't higher than 70?? When was the last time you checked?