Mustard Algae... how long to keep FC high?

[akenis]

So for the last 3 years in coastal FL I have dealt with repeating bouts of MA during Summer. I am in full sun and wading birds like to visit my pool....Herons, Ibis,Egrets, etc. I now believe they are the source of my recurrent problems. This latest round of MA has been eliminated. Based on CYA of 70, I had FC at 41 for a day. Pretty sure everything is dead and the water looks and feels great.

So based upon CYA/FC charts, and since I have a history of MA, I should keep my FC at 15% of 70 CYA, or 10.5 min to prevent it from resurrecting from the dead. How long do I need to maintain this high level? I normally run my FC at 4.5% CYA with SWG running 12 hrs a day. I'm bumping that up now.

When can I stop with the 15 % FC... end of the season is what I've seen. How is that defined? Maybe when day temps are below 85 and night temps stay below 75????

Not fun having to do the FAS/DPD everytime I check FC.

 

[Mdragger88]

Just to confirm,
Did you complete the
SLAM Process at regular slam fc levels before proceeding to the MA slam level and protocols for 24 hours?

As for the sustained elevated fc - ma minimum.
Some people do it for several weeks, some for the rest of the season, some indefinitely. If you let it fall below ma minimum & the ma reappears you just go back up.
I wouldn’t suggest going back to maintaining 4.5% of your cya as your target.
That’s minimum & riding minimum is asking for algae if the slightest thing occurs.
As someone who has fought MA I prefer to maintain at least 10% of my cya at minimum - this leaves plenty of wiggle room for error & maladies like wildlife, high bather loads, higher uv days, organic loads, equipment failure, etc.
Its also easy to figure.

 

[JJ_Tex]

So based upon CYA/FC charts, and since I have a history of MA, I should keep my FC at 15% of 70 CYA, or 10.5 min to prevent it from resurrecting from the dead. How long do I need to maintain this high level? I normally run my FC at 4.5% CYA with SWG running 12 hrs a day. I'm bumping that up now.

Keep in mind that 4.5% of CYA is the bare minimum, as in never ever ever go below that number.

Looking at your logs you flirted with the minimum quite a bit and even were under on several occasions, so good for you to bumping up your targets. I too have a SWG and CYA of 70. Even though the target is 5 FC per the FC/CYA chart, I get really nervous when I get close to 5 and like to keep my FC 8-10 (and I dont have birds in the pool, so feel free to go a bit higher).

Also note that the DPD test is accurate, but you can still use the block test for a quick ballpark check. See my signature and that nice orange doesnt tell me if I'm 8, 10 or 12 FC but it certainly tells me I have a sanitary pool that is safe to swim in with no algae concerns.

 

[akenis]

Just to confirm,
Did you complete the
SLAM Process at regular slam fc levels before proceeding to the MA slam level and protocols for 24 hours?

Yes. Had it at 28 ppm all day. Held overnight. Then bumped to 41 ppm for 24 hrs. Pool was never really bad. Just not super clear. When I brushed steps and shelf on Fridays there was a little fall out that turned water a little greenish. I kept trying to convince myself that it was just pollen or dust/dirt accumulated during the week.

Thanks. Good points. My target was 5 ppm. Definitely got too low a few times this summer. Jandy SWG panel was dying. Several times it shut itself off. Last week it was stuck at 65% and wouldn't accept changes. $300 bucks for a new cover with the LCD and keypad.

How inaccurate is pH test when FC is around 10-12 ppm?

 

[reggiehammond]

Thanks. Good points. My target was 5 ppm. Definitely got too low a few times this summer.

You'd be wise to treat 5 as the minimum and target 10. If you target 5 and have any sort of issue, BAM, you're below minimum and you have opportunity for algae.

 

[akenis]

You'd be wise to treat 5 as the minimum and target 10. If you target 5 and have any sort of issue, BAM, you're below minimum and you have opportunity for algae.

Good plan. Thanks.

Hey I was just wondering....is daily chlorine demand dependent on FC level? IOW do you have to add more chlorine to maintain 10 ppm than to maintain 5 ppm?

Say you are at 5 FC and maintaining with SWG running 12 hrs at 60%. Add liquid chlorine and bump to 10 FC. Will the same SWG setting maintain the new level?

I'm guessing there is probably a little more daily burnoff when FC is higher.

When I was at 41 FC, turned SWG off. FC dropped about 10 the first day. And about 10 the next day. Day 3 it dropped from about 20 to 14.

 

[Katodude]

It does burn off more when it is very high. That is one of the reasons the SLAM level is not higher. But at around 10, it’s not going to make that much of a difference.

This is Florida, there are constantly organics coming into my pool. I can be away for a weekend and a HUGE rain can cause my salt level to drop. It’s just constant assault on the pool. The way to manage that is keep your FC hot. I actually like my FC around 14. I consider 10 my minimum. That way I know if anything happens my pool will alway be in good shape.

 

[reggiehammond]

Say you are at 5 FC and maintaining with SWG running 12 hrs at 60%. Add liquid chlorine and bump to 10 FC. Will the same SWG setting maintain the new level?

Just to be clear, the SWCG is dumb. It doesn't know your FC levels; nor does it care.
If your normal daily FC demand is 4ppm (3-5ppm daily is normal) and your SWCG is keeping up (Ie. FC at 6pm yesterday was 5ppm, and today at 6pm it's 5ppm) then raising the FC level using liquid should allow SWCG to maintain that higher level.

 

[Mdragger88]

I don’t notice a difference in fc losses at the higher target - I keep my fc 8-10ppm
it’s basically a one time increase in fc and the same daily maintenance settings after.
About ph test-
the further past 10ppm fc you go the more skewed it becomes.