Can you get algae when your levels are good?

[zrtman]

Started up pool at beginning of April. Did a SLAM because it had turned to swamp. FC was 30 and CYA was 35 for SLAM. Held FC for 8 days. I let it drift down to fc of 6 and did the overnight loss test and it was 0. CC was 0. Pool was still a little cloudy, but it is a small sand filter (Green disappeared within a day) It took a another week for cloudiness to go away.

Now a couple weeks later pool is very clear but almost looks like green algae on bottom and partway up the sides. Not sure how this happen... I have SWG that keeps pool at a min of FC 4. I check it often. CC is still 0. CYA is 45, PH is low @ 7.0.

Not sure if it is algae or just debris. It sweeps off very very easy. Pool has not been used and not been vacuumed or otherwise stirred up. Maybe I should have done SLAM for longer length of time but all other tests were ok?

 

[PoolStored]

Started up pool at beginning of April. Did a SLAM because it had turned to swamp. FC was 30 and CYA was 35 for SLAM. Held FC for 8 days. I let it drift down to fc of 6 and did the overnight loss test and it was 0. CC was 0. Pool was still a little cloudy, but it is a small sand filter (Green disappeared within a day) It took a another week for cloudiness to go away.

Now a couple weeks later pool is very clear but almost looks like green algae on bottom and partway up the sides. Not sure how this happen... I have SWG that keeps pool at a min of FC 4. I check it often. CC is still 0. CYA is 45, PH is low @ 7.0.

Not sure if it is algae or just debris. It sweeps off very very easy. Pool has not been used and not been vacuumed or otherwise stirred up. Maybe I should have done SLAM for longer length of time but all other tests were ok?

I would go back and slam again...you missed one of the exit criteria for a slam..."Clear Pool." Don't stop until you pool is clear.

SLAM Process

Also, don't maintain with SWCG at minimum. Keep it at the high end of the recommended range for your CYA. Covers heavy usage days.

I printed out the instructions and read them a bunch of times during the slam. I missed the part on scrubbing ladders...took me three more days because I didn't read the details.

 

[Mdragger88]

FC was 30 and CYA was 35 for SLAM.

Slam level fc for a cya of 40 (35 counts as 40) is 16ppm
FC/CYA Levels going over just wastes chlorine & risks damage to surfaces equipment & swimmers

Held FC for 8 days. I let it drift down to fc of 6 and did the overnight loss test and it was 0. CC was 0. Pool was still a little cloudy,

You’re supposed to keep fc at slam level until you pass the
Overnight Chlorine Loss Test @ slam fc levels
&
the water is crystal clear (no algae dead or alive)

You ended the
SLAM Process prematurely without meeting the exit criteria.

Now that your cya is 50 (45 counts as 50 - no inbetweens, round up) your slam fc level is 20ppm. Maintain 20ppm until you pass ALL 3 end of slam criteria- not just 1 or 2.

 

[zrtman]

Thanks guys for the input. Will try again. The filter on this pool is not that great - just a small sand filter. It never gets it crystal clear. When I vac the bottom - alot of it comes right back out the return... so was thinking after 8 days it was as good as it was going to get.

Just brought it back up to 24.. over shooting on purpose a little.

Thank you for the input.

 

[PoolStored]

Just brought it back up to 24.. over shooting on purpose a little.

Slam level is safe for people, pool (liner) and equipment. It is not about the level, it is about the duration and maintaining. Don't over add.

 

[zrtman]

Can you use the pool while at 20?

 

[PoolStored]

Can you use the pool while at 20?

Yes, AS LONG AS YOU CAN SEE THE BOTTOM. Safety.

 

[zrtman]

Yes, AS LONG AS YOU CAN SEE THE BOTTOM. Safety.

It is not that cloudy - could alwwys see bottom. Was thinking 20 was too high to swim in. Was is the limit for swiming - I do not recall seeing that number here.

 

[PoolStored]

It is not that cloudy - could alwwys see bottom. Was thinking 20 was too high to swim in. Was is the limit for swiming - I do not recall seeing that number here.

It is safe to swim up to SLAM level for YOUR CYA level.

Aqua Magazine: CYA and Chlorine in Plain Language

IMO, the most important quote from that article is

With a CYA:FC ratio of 20:1, the concentration of HOCl stays pretty constant at 0.02 ppm.

Which means that 20 ppm CYA and 1 ppm FC is virtually the same as 200 ppm CYA and 10 ppm FC. With 3 ppm FC and zero CYA (perfectly safe and ideal according to the CDC) a body of water with pH of 7.5 at 80 degrees F would have an HOCl of 1.451. A pool with 2.5:1 CYA:FC concentration (SLAM Level) would have roughly 0.3 ppm HOCl. So a pool at SLAM level has only 1/5th the active chlorine (HOCl) as a pool that is within CDC guidance for safe and ideal. More chlorine can be less harsh, one of the most difficult things for anybody new to TFP to buy in to until it is experienced.

I will allow the rest of the article to speak for itself. Please keep in mind that the article, while following the same science TFP has been promoting for well over 10 years, was not written by anybody at TFP and may differ in some of the conclusions.

 

[zrtman]

Thank you!