Could this be algae or dirt/pollen?

[chem geek]

If it's powdery and yellow or mustard color, then it's likely to be yellow/mustard algae and that takes more chlorine to kill and to keep away. I would shock at a higher level 20-25 ppm FC and you can lower your pH some (say, to 7.2) before adding the chlorine since the large amount of chlorine will raise your pH (which makes it a little less effective). Keep the chlorine up until the powder is gone and does not reappear and keep brushing it so it mixes with the water and gets full exposure to the chlorine.

You probably had your CYA too high at 60 since that would mean needing to keep your FC at a minimum of about 7 ppm FC. If you maintain 30-40 ppm CYA, then you could keep a minimum of 5 ppm FC (maybe a little less) and probably keep this mustard/yellow algae away. Some users report that they need a higher chlorine level to keep the algae away -- roughly the Max level on Ben's chart or the 0.07 column in my chart while others are OK with the mid-levels or the 0.05 column.

Do you remember what your FC level was when this algae first appeared? That will help us confirm or adjust our recommendations.

Richard

[joliecharlie]

As I posted... my chlorine reading was 15ppm last night
No CC ever

I checked this morning and it is still 15 ppm!

So maybe I have over reacted but this stuff sure looks funky. It is like a red dust, just like the photos at the beginning of the this thread.

It dissipates into a cloud when brushed. There is just a little bit of it this morning.

We have lost CYA via dumping excess water due to heavy rains and backflushing. We normally keep the CYA higher because we have full sun exposure ALL day and cannot keep chlorine. Keeping it higher has pretty much solved that problem. It may not work for everyone, but it works for our pool.
Thanks

[Watermom]

Sorry - for some reason, I just didn't see where you had posted your chlorine reading. I'm gonna let ChemGeek help you with this. I'm actually out of town and just popping on to the forum on a laptop. Getting ready to head back to Charleston in a little bit. ChemGeek or somebody else will be around this afternoon and can give you some help. Good luck.

[chem geek]

Well, if your chlorine is holding, then it isn't breaking anything more down and if the dust or algae or whatever it was is gone, then it is probably killed and filtered or broken down. If it was truly red (the pictures at the start of this forum look more green/yellow to me and that's more like mustard/yellow algae), then this could either be non-algae like dirt or could be a red algae (there is that type of algae, but it's usually not found in pools as far as I can tell).

Anyway, it does sound like you've solved your "red dust" problem. On the CYA amount, I am surprised that 60 ppm CYA makes that much of a difference compared to 30 ppm CYA. In theory, it would only increase the half-life of chlorine (in direct noontime sun) from around 6 hours to 7 hours which isn't that much of a difference. Of course, whatever works for you is what is best.

Let your chlorine drop to "normal" levels but keep it as suggested at around 6 ppm FC or so minimum (at your current 40-50 ppm CYA level) and see if this stuff returns. If it does, then you can try shocking to higher levels (20-25 ppm) as I mentioned in my earlier post.

Richard

[joliecharlie]

Let your chlorine drop to "normal" levels but keep it as suggested at around 6 ppm FC or so minimum (at your current 40-50 ppm CYA level) and see if this stuff returns. If it does, then you can try shocking to higher levels (20-25 ppm) as I mentioned in my earlier post.

Richard[/QUOTE]

Hi Richard,
Just checked the chlorine after full day of sun and 80-85 degree weather here in NC.
FC has dropped by 5ppm since this morning. (Remember it held stable overnight at 15ppm)

Is it normal to lose that much chlorine in a day?

[chem geek]

That does seem a bit high for a drop. Losing half of the chlorine over a day is more typical -- so 15 ppm to 7-8 ppm would be more "normal". Then again, I could be wrong about those half-life numbers. They seem to be correct for most pools, but there's no arguing whatever it is that you are seeing in your pool. It's also not like you are in south Florida or the middle of summer. Maybe there is in fact some algae in your pool and it is growing more during the day and consuming more chlorine, but typically if it holds overnight then this means the algae is gone. Sorry I don't have a good answer for you.

Richard

[chem geek]

OK, I've been thinking more about this and I believe you do still have a chlorine demand with this (presumed) algae. It's probably a demand of 1 ppm per 8 hours or maybe a little more. That would "seem" like the chlorine holds overnight, but if you lose half from the sun 15-->7.5 and then another 2 or more from chlorine demand from the algae, then that would get you to 5.

So, I would suggest really hitting this algae with a lot of chlorine. Start with 30 ppm FC in the morning. If you are able to stick around and add more chlorine during mid-day, do that, otherwise add more when you get home at night. Keep this up until 1) there is no more visible red dust and 2) the chlorine holds solidly overnight (virtually no drop at all) and holds more during the day so it drops no more than half.

If that works, then the question becomes how to keep this algae away ongoing. Though you could maintain a minimum of 6 ppm FC at 45 ppm CYA (or 8-9 ppm FC at 60 ppm CYA) which is what some others have found is required to keep away mustard/yellow algae, there is another way that might let you keep lower chlorine levels. See this thread for the use of 30-50 ppm Borates in the pool which act as an algaecide (as well as an additional pH buffer). The problem is that we don't know if this is a good algaecide specifically against mustard/yellow algae though it does inhibit a variety of different algae. Anyway, I just wanted to give you a long-term option that might help since this is a repeated problem for your pool that would require higher chlorine levels to keep away (even at 30 ppm CYA, you might have to keep a minimum of 5 ppm FC to keep away mustard/yellow algae instead of the normal 3.5 ppm FC mid-point recommendation).

Richard