Understanding Algae

[DirtyRat91]

Or, perhaps a better title would have been "I want to understand algae". I'm hoping some pros will enlighten me.

I was on the verge of posting in the SWG section of the forum, complaining that my newly repaired SWG is under producing. However I'm almost positive it's likely doing just fine, but my pool has an unusual appetite. I returned from a 8 day vacation after JUST repairing my SWG the night before we left, to find barely 0.5 FC in my pool. Despite skimmer chlorine sticks and my SWG going, I have almost no chlorine. I boosted output to 100% and ran it overnight to find 1 FC in the morning. No CCs. Water is crystal clear. However I'm almost positive algae is growing. The walls of my new vinyl liner are very slick...this is new after a month. I wanted to see how long I could keep perfect water following a fresh water fill during the liner replacement. The answer: Not very long at all.

So basically, I've got beautiful water. I can see from wall to wall underwater (32' across) >almost perfectly<, the slight haze in the water is one indicator. The slimey walls is another indicator. The endless FC appetite is another.

What I want to understand is why can 5 FC MAINTAIN an algae free pool, but it cannot overcome algae once it has gotten its foothold? I didn't want to SLAM my pool. I know folks are going to tell me "It's totally fine, it won't fade your liner." I just replaced a WHITE liner, (95% faded from blue) and have the most beautiful pool I've ever swam in. So I'm hesitant to raise chlorine levels. I believe you guys when you say it is fine...I do...I'm just mad that I let the FC drop to algae growing levels. However I'm certain algae is present, and I need it gone before the SWG can return to regular maintenance mode.


(Chlorine sticks were added to help CYA level raise while dosing FC while my SWG went down. I wasn't sure I'd have an SWG during vacation. So with the sticks the newly repaired SWG was on low production (50%). However I had low FC due to water leak/broken SWG. Water leak let CYA drop too. I'm 100% comfortable with testing, and adding the appropriate non-pool branded products to keep pool chemistry in check. I'm a seasoned TFP veteran. But I'm curious to better understand my enemy, the algae.)

 

[Shirker]

What is your CYA value? If it is low after doing a refill it could cause FC to drop through the daylight hours. What is the output rating for your SWG?

 

[frogabog]

What are your full test results? Are you brushing the walls? I have a feeling if what you're feeling on the walls is true, brushing will break that free and allow the chlorine in the water to attack it. Don't be surprised if your FC plummets after this. I'd suggest to raise FC before brushing to SLAM level.

I believe to answer your question, in short is that maintaining FC does not allow algae to grow in the first place. Once it has grown however, you need more than maintenance levels to kill it.

Your liner is safe as long as you are at or below SLAM level for your CYA level. I know it sounds scary with your pretty new liner, but TFP history of lots of SLAMmed pools shows this to be true. A full set of test results will help. What test kit are you using?

 

[ajw22]

Circupool SJ-40 can produce 1.6 lbs of chlorine a day if run at 100% 24/7. Plenty of capacity for a 14K pool.

Do a Overnight Chlorine Loss Test. It will tell you if you have algae.

 

[JoyfulNoise]

Algae replication rates in warm water with insufficient sanitizer can be high enough such that there is a colony doubling every 2 to 4 hours (depends on species, light requirements, etc). So in a 24 hour period with light available for more than 12 hours per day (summer time), algae grows very fast. The kill rate of any sanitizer is concentration dependent. There's not a lot of hard data on the CT kill rate for algae with chlorine, at least no easily available data, but once your active chlorine levels (that would be the hypochlorous acid part of the FC) fall below 100 part per billion (0.1ppm), the kill rates are well below the colony doubling times. So basically, algae can freely grow and thrive when there is (insufficient) sanitizer around. Despite what you might think, your water is not one, homogenous mixture. While your water sample might say there's 0.5ppm or 1ppm FC, there's a very good chance that water right at the surface of the pool has no chlorine in it whatsoever (UV light destroys chlorine quickly) and the water nearest the walls probably has much lower FC levels.

 

[DirtyRat91]

Circupool SJ-40 can produce 1.6 lbs of chlorine a day if run at 100% 24/7. Plenty of capacity for a 14K pool.

Do a Overnight Chlorine Loss Test. It will tell you if you have algae.

I did the math once, and it made since at the time. (My hourly run time/% level) Figured the FC production per day, and it all added up. Feeling lazy now, so I'm assuming that the 1.6 lbs equates to trichlor per the pool math site? If so, 1.6 lbs, or 25 oz = 7.5 FC per day. (EDIT: That's 7.5 CYA increase, my mistake, a 12 FC dose, so I would've been around 3 FC per day at my other rate/runtime) >OLD WRONG POST CONTINUED< I think that does work out, as I was running the pump mostly just during sunlight hours, at 50%, so my production would've been down around 2 FC per day, or what I was dosing when I used bleach.

I won't turn this into a posting test #s post. I appreciate the well intentions, but trust me, I've got that. I've got a TF-100 kit, I know the CYA level/chlorine relationship. The suspected algae growth is due to several factors. Cavalier water prep, a BAD water leak on the return, which allowed produced chlorine to never make it to the pool & severe water dilution due to adding a couple of inches of water every other day. The dilution affected my CYA and salt levels. And my SWG failed after I figured out and worked a temp fix to my water leak problem, which allowed FC to drop again. I do know that the best course of action is to SLAM, the post was a whining "Why me?" type post having algae in very new water with the hope of learning something about algae.

I've theorized about exactly what @JoyfulNoise is suggesting. That poor circulation could play a large part in test numbers looking ideal, and a pocket of algae forming in a spot of the pool where sunlight is direct, and water movement is poor. The algae could grow in strength there and start to creep around the pool before showing the more typical signs. (Color, cloudy water) I've balked at suggestions by some folks to just run 1 return and not use the leaking return. Or plug the main drain suspecting water leak may come from there. I want the main drain pulling, the skimmer pulling, and both returns operating normally to help swirl the pool water and promote max circulation. I prefer the pump runs most of the daylight hours, taking a break for a few hours during typical swimmer time, as water circulation gets plenty of help from the kids.

I did play around with pump on/off times when I first got my timer. I noticed if I got in the pool without the pump running for a while during the day, there were pockets of VERY warm water. This leads me to believe even though the pool may have a 4 FC chlorine level, that certain areas could get zapped to nearly nothing, and if conditions were right, and some leaves fell into the pool, algae could get a foothold. While I didn't play around with it much, I decided I wanted the pump working during highest sunlight hours, and theory being, a well mixed pool in the evening likely won't have radical FC deadzones.

 

[duraleigh]

I noticed if I got in the pool without the pump running for a while during the day, there were pockets of VERY warm water

I haven't read this thread but this JUMPED out at me. You should never have pockets of warm (or cold) water, You are not running your pump often enough or you have a serious issue with your circulating system

 

[ajw22]

I believe the SJ30 uses a 2 hour cycle for its generation %. Breaking up the pump runtime into multiple cycles will not give the FC output PM calculates.