Possible to have a tiny bit of algae?

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Scooch

Scooch

0
Jul 16, 2013
29
I've been a member here for 3 summer seasons and it's been great. Hoping someone can point me in the right direction on something. First, the details...

-11,000 gallon above ground pool with vinyl liner in CT

- FC hasn't been below 2 ppm all season and is typically between 4-6ppm
- CC has never tested above 0.5 and is usually at or close to 0.
-pH is rock solid at 7.5 all the time
-TA is 80 and has been 80-90 all season
-CYA is 30-35

Recently I noticed what looked like tiny algae blooms on the bottom of the pool. They're barely an inch wide and a very faint green. Seems like they settle into little dips in the pool floor. The water looks crystal clear from a distance, though. You gotta strain to see these little things.

Yesterday I vacuumed, brushed and dumped a little extra liquid chlorine in at night. I run my filter 9 hours each night from 10pm-7am. Tested this morning ( I have a TF 100 test kit) and there wasn't any significant FC loss, yet that tiny algae is there in the same spots (5-6 in total) that were there yesterday.

Do I need to SLAM? Could it possibly be something other than algae? I had algae when I opened the pool in May, but Slammed for 4 days and it was cured (actually turned clear after 1 day but I kept at it to be safe). Would the FC be stable and CC not rise above 0.5 with algae present?

Any advice would be much appreciated!
 
With the CC at or below .5, I would hesitate before doing a full SLAM. If it were my pool I would just raise the FC up to about 10 for a couple days, brush all those areas, and see what happens. With a CYA OF 35 you can use the pool as long as the FC is at or below 14. That way the pool is still usable. A SLAM puts the pool out of service, and you have so little left of the season.

If it doesn't clear up in a few days there is always plan B.

BTW: There is no such thing as a "tiny bit of algae".
 
woodyp said:
"Tested this morning and there wasn't any significant FC loss,"

How much we talking and how did you test? Was this an OCLT?
Click to expand...

Used my TF-100 test kit and did the FC/CC test (so, yes, I believe that counts as OCLT). Went from 9 to 8.5... BUT realized I had a puck in overnight (I don't normally use pucks but I had one in the past week to boost the CYA a little).
 
Scooch, just something to keep in mind if you're on the fence about the OCLT:
When performing the OLCT, remember that it must be done when the sun has dropped – no sunlight on the pool. About 8 hours minimum is recommended. Also, your FC level should be elevated more than normal. Starting FC could be at/close to your SLAM level, but no lower than 10. Anything less than 10 FC and you may not receive an accurate portrayal of FC loss (by percentage), even if it’s only 1 ppm loss.
Click to expand...

- - - Updated - - -

And I agree with Chief ... ANY algae is too much algae. Before you know it, there's an algae party going on. :party:
 
Thanks all, I really appreciate the replies. I'll do a more rigorous OCLT test tonight/tomorrow.

And I totally get the "there is no such thing as a little algae" perspective. I've read here that a pool is unsafe with algae present, hence my concern! Didn't know if there was a safe/unsafe line.
 
I realize there are electric rate discounts in many areas for running in off peak hours but I suggest running that pump for an hour or so a few hours apart a couple times during the day to keep the water stirred up.

Also, to me your FC level is at the low end for your CYA. If you are off a little on your CYA measurement 2 ppm may be risky, IMHO. For a CYA of 35-40 your minimum is 3-6 ppm.
Personally I would bring it to 7 and let it drift down to 4 or 5, not 2. If you get a little more sunshine one day or a little more heat or swimmer load it could be trouble.
 
Thanks Wildcat. The FC of 2 is rare, I almost always have it in the 3-5 range, but I will try to push it higher given the CYA. I've had a puck in for the past week or so to try and raise CYA since we're in the first heat wave of the summer here in CT.


And you're not the first person advising me to run the pump twice or more a day. Challenge is that my timer only allows me to set it once, so the other time would need to be manual. Not impossible, just a pain, but maybe it's necessary.
 
Scooch said:
Thanks Wildcat. The FC of 2 is rare, I almost always have it in the 3-5 range, but I will try to push it higher given the CYA. I've had a puck in for the past week or so to try and raise CYA since we're in the first heat wave of the summer here in CT.


And you're not the first person advising me to run the pump twice or more a day. Challenge is that my timer only allows me to set it once, so the other time would need to be manual. Not impossible, just a pain, but maybe it's necessary.
Click to expand...

If you have "mechanical" dial timer with the little arrow stops it possible to get a second set to allow for split running.
In the reviews for these clips for an Intermatic timer (supposedly the most common type) one reviewer mentioned they bought a second set to set up two cycles. Under $10.
 

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Update (if anyone cares!)...

Did a proper OCLT. Was 10.5 at 9:30pm and 9.0 at 7:30am. CC appeared to be zero (or darn near it). On the bright side there were only a couple little spots of algae on the floor this morning, definitely an improvement from yesterday.

Added another 30 oz. of liquid chlorine (12.5%) this morning to get the FC to 12 and running the filter all day with the return angled diagonally down to try and keep stirring up the bottom. Also brushed the spots to get that algae off.

Fingers crossed.
 
Of course we care Scooch. :) Happy to see you are seeing some improvement. You also did the OCLT at a higher level which helped to confirm you still have a little organic material taking your FC. Stick with it though. Hopefully your SLAM will not be too much longer. Maybe you'll pass the OCLT tomorrow.
 
Thanks TS! I also just realized I messed up the OCLT. I measured the FC at 7.5 just after sundown and then added 30 oz of LQ. So the 10.5 I reported was an approximation. Just dawned on me that I wasn't supposed to add any chlorine once I got a measurement to start the OCLT. Man, I'm usually MUCH better at following instructions!

But progress was definitely made regardless of my screw up. I'll get the OCLT process right tonight!
 
This situation is driving me a little nuts. Since Sunday I've been running my filter nearly 24/7. I've amped up the FC level to 10-11 repeatedly, and it's only dropped as low as 7.5 (and only for a little bit before I raised it again).

The CC level has either been 0 or darn close to 0 the entire time.

I've done two correct OCLTs the past 2 nights and I've lost just 1 FC each night.

I've brushed the floor and walls vigorously every day.

Plus aside from these darn little green spots on the pool floor the water is crystal clear.

So all the math seems right but I just can't kill this darn algae.

I guess I need to do a full blown SLAM but with maybe 3 weeks left in the season I so hate to take the pool out of commission.

Very frustrating!
 
I would push the FC over SLAM for overnight and let it sit at just under during the day so you can use the pool during the day/evening. It might take a little longer but at least you will get to use the pool!

Kim
 
Something else to consider Scooch, at the beginning of this thread you listed a CYA of 30-35. If it was closer to 35, you might as well say 40 for CYA/Chlorine chart purposes. That would make your SLAM FC 16. That could explain why you're just shy of completing the SLAM. You're doing everything else right, so perhaps as Kim already stated, raising the FC a bit higher is what is needed to compensate for the CYA reading. Just a thought.
 

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