High FC vs Phosphate testing

[CarlD]

Carl & Richard:

Why do you guys think I go to a pool store? I don't have a pool store in my town, and nobody has sold me on anything. Not sure what I said to get that type of response (?) but it's just me, myself and I here in SW Michigan. As my original post states, I use the Taylor K2006 for my testing. I also posted my CYA was between 40 and 50, but it's not above 50. Seeing the "black dot" disappear is certainly subjective, but my eyes aren't THAT bad. Not sure what any of that has to do with my original post, but wanted to respond. Thanks for the help.

As BigDave said, when someone starts talking phosphate levels, we assume they were talked into it by a pool store. Why? Because other than discussions amongst the support team, you are, I believe, the FIRST person to mention them WITHOUT being pushed into it by a pool store! Leslie's has a whole phosphate reduction package plan, selling regular doses of reducer--and it is (or was) a big money maker for them.

We are just trying to help and when we see apparent anomalies, we question the test results that lead to them. That's all.

[TCP007]

BigDave: No water change, but yes... I stopped adding granular dichlor since I super-chlorinated with liquid chlorine in late July. A mod here recommended I stop adding sanitizer until my FC was at or below 5ppm. I actually added my floater back to the pool in mid August because I was worried about not having any sanitizer whatsoever. The floater holds about 1-lb of 1" trichlor tabs that typically dissolve in about 1 week. But that's the only sanitizer I have added since late July until about 2 weeks ago. I test my water every Saturday, and my FC was still at 7ppm the week prior to this last, minor outbreak.

I buy online from InTheSwim. I've never spoken to anyone there. The information about phosphate testing is right in the Taylor booklet. I can't be the first person to ever decide that testing for phosphate might be a good idea (?)

Anyway, the pool is ready to be closed. I didn't realize phosphate testing was the Loch Ness Monster of pool maintenance. Nothing ventured, nothing gained.

[CarlD]

Usually, nobody says let your FC drop below 5ppm unless you're dealing with a metals issue.

Are you aware that Dichlor adds lots of stabilizer/CYA, and so does Trichlor, and that Trichlor is also very acidic? Liquid chlorine/bleach adds nothing but chlorine so it's always safe to use.

We generally do NOT recommend phosphate testing because, except in peculiar cases, it's USELESS.

However, it is your pool and the ultimate responsibility for it is yours. We can only make suggestions.

[FormerBromineUser]

TCP007 has been talking to someone as he has 23 posts, but only 3 show up to us NIP's. Would be interesting to see more history, especially to clear up the 5 FC question. Good luck with your closing, 007!

[BigDave]

FormerBromineUser makes a good point, this thread seems to be missing context. I found TCP007's earlier thread in the getting started forum and re-read it. Here's a quick review as I understand the situation. Please correct as necessary.

Before coming to PoolForum, TCP007 was having a bad season this year with recurrent algae. TCP007 read some of the posts here and decided to shock with liquid chlorine.
TCP007's pool had little or no CYA when first tested with a K-2006 and after the bleach(LC) shock FC and CC were quite high.
Granular CYA was added and the rate of FC loss slowed. No more chlorine of any source was added before this thread was started.
As the shock chlorine was eventually consumed, the pool developed algae once again.
TCP007, being the resourcefull sort, read the blue book that comes with the K-2006 (we usually tell people to throw it away) and found that phosphates can contribute to algae growth.
TCP007 sought to mitigate the influence of phosphates with a phosphate remover.

So, back to basics.
Pools need sanitizer (chlorine) to remain clean and safe.
Pools need stabilizer (CYA) to protect chlorine from sun exposure.
Pool water must have a pH between 7 and 8 for swimmer's comfort and to protect the pool and equipment from damage.
Concrete / plaster pools must have calcium in the water to help prevent the water from taking it from the pool walls.
Pool water needs a balance between calcium hardness, total alkalinity, and pH to prevent calcium scaling on one hand and calcium leeching on the other.

Earlier in this thread I think I wrote about identifying mustard algae; Do you have it?
Please provide a complete set of readings from your K-2006.

If FC is less than 10% of CYA, get some chlorine in there ASAP. We like bleach best as it has fewest side efects.

[chem geek]

BigDave: No water change, but yes... I stopped adding granular dichlor since I super-chlorinated with liquid chlorine in late July. A mod here recommended I stop adding sanitizer until my FC was at or below 5ppm. I actually added my floater back to the pool in mid August because I was worried about not having any sanitizer whatsoever. The floater holds about 1-lb of 1" trichlor tabs that typically dissolve in about 1 week. But that's the only sanitizer I have added since late July until about 2 weeks ago. I test my water every Saturday, and my FC was still at 7ppm the week prior to this last, minor outbreak.

1 pound of Trichlor tabs in 35,000 gallons would only be 3.1 ppm FC of chlorine (and 1.9 ppm CYA) so if that's the only chlorine you've added from July until 2 weeks ago, that wasn't nearly enough since that's only 0.44 ppm FC per day. More usual daily chlorine loss is 2 ppm per day. Do you have a solar cover? Is your water temperature cold?

I suspect that your chlorine level was low for an extended period of time and that allowed algae to grow. Once algae is established, however, it takes higher levels to kill it which is why we recommend shocking the pool to higher levels to kill off the algae.