Ok, I give up. What's happening in my pool?

[prov431]

I have read countless threads on how to maintain my pool, and I have learned a great deal.
Unfortunately, I am still at odds as to what is happening in my pool.
What I am seeing is after 2 to 3 days, I continually get a return of something on the vinyl liner. When I brush it, the appearance is a greenish smokey cloud.

I have been keeping my FC at or above target value for my CYA level. The pool water looks great, has good clarity, doesn't smell, taste, or otherwise look bad. I vacuum with a manual vac only as needed (maybe 1x every 2 weeks based on weather)
I backwash my sand filter more than necessary.

Can anyone tell me what's happening? How can I have algae with no CC showing? (I use the FAS/DPD test, daily)
I just got off a round of shocking about a week ago, for pretty much the same thing...only it was worse since I was not home for a few days.

My pool is:
18,000 gal inground vinyl liner
300 lb sand filter with bottom drain, aqua genie side skimmer, and 5 additional returns.
The filter runs on a timer for a total of 9 hrs per day
Tonights numbers (before brushing and adding bleach)
FC - 5.5
CC - 0
PH - 7.4
TA - 80
CYA - 40-50 (someone find me a better test than the black dot!)
Temp - 90

Any help is greatly appreciated!
Thanks in advance!
-Dan
North Carolina

 

[Axl]

Hello Dan, I wish I could give you some wonderful advice, but I am just a newb. (only had my pool for a short while) It seems that you have algae but your numbers that you posted do not indicate that at all. While you are waiting for an expert to post, I figured that I would say hello, since I am in NC as well. Burlington area. :-D

You have come to the right spot. The pro's here will surely help you get you water free from your green stuff fairly quickly.

 

[AnnaK]

IMO, that's not algae but just plain 'dirt'. Not that you have a dirty pool, mind you, but just saying that you have solids that settle out of solution after a few days to become visible. Every pool that's fallow, so to speak, for a few days at a time will have that. It's in the air: pollen, pollution, dust. My observation is that unless the water is used daily and the solids are being kept in solution, they will eventually settle on the bottom.

You said you backwash more than you probably should. My understanding is that used sand filters better than clean sand, so maybe you could cut back on the backwashing some? Tough I don't think it'll make much of a difference.

Your chemical balance seems ok, you're on top of it with the maintenance. If it were algae, you'd know it. Algae says 'algae' when you have it. It's like recognizing the buzz of a rattlesnake even if you've never heard it before. Vacuum the stuff up, or jump in and swim and stir it up that way.

I tend to not sweat the small stuff. I vac if it bothers me, or I brush it up into a dust cloud, run the filter, and go swim.

 

[mbb]

I'm with you Anna...my idea of clean has changed alot!
I have been trying to keep up with the dust, dirt and pollen in this drought ridden state of NC. I have been about to wear my robot out running it daily!
My new philosophy is that if numbers are good and no slimy feel...I'm happy!

 

[duraleigh]

Dan,

You need to check your ability to hold FC overnight. When the sun is off the pool, test FC and record. The next morning, test and record again for FC. If your FC drops more than 1.0 in that time period, (which I think it will) you have algae and need to shock.

 

[Guest]

I'm with Dave (duraleigh) on this one! If you do this and DON'T have any FC loss overnight then it's just dirt and pollen.
Otherwise, start shocking!

 

[prov431]

Thanks for the replies and advice.
I will get a FC number tonight after the sun gets off the pool and the again first thing in the morning. I'll post up the results.
BTW - the new FAS/DPS chlorine test is SWEET!

And, just because I am officially confused:
I thought that if you did not have any CC number, then you didn't have algae? I'd swear that's what I read on many threads?

Thanks again!
-Dan

PS- HELLO North Carolina!

 

[Guest]

And, just because I am officially confused:
I thought that if you did not have any CC number, then you didn't have algae? I'd swear that's what I read on many threads?

Thanks again!
-Dan

PS- HELLO North Carolina!

Not aways true. If you are losing chlorine (have a chlorine demsnd) then agale is always a suspect. it is possible that you have enough FF in the pool to kill a nascent algae bloom and take care of any CC that forms and the only thing you will see is the inability to hold FC.

 

[prov431]

Ok, thanks for the explaination regarding the CC.

I just tested the pool, without adding any CL since last night. I read 5ppm FC and 0 CC.
I didn't bother with the other numbers since I got a full set yesterday.
I'll check the FC in the morning and see where it's at.
I hate waiting, since the 5ppm is a bit on the low side for my 40-50 cya level min.
Oh well, I'll get back with you with the results!
Thanks for the help!

Dan

 

[prov431]

Well, the results are in from early this morning:

FC - 5 ppm
CC - 0

I brushed the sides and shallow end again, before adding bleach. (same dusty, greenish brown cloud, but not enough once all brushed to cloud the water very much. It was more prevelant in the shallow end and on the sloped sides of the deep end) I'm guessing the suspended solids settling out is the correct answer...or is it something to do with the less deep areas of the pool surfaces?

Thanks again,
Dan