Phosphates and algae

[cood60]

My phosphates are apparently quite high. (2500) I have no way to test with my tft 100 kit so I took water to the pool store
Do I need to lower the phosphate levels and if so what is best way to approach this?
FYI, our city water comes with 200ppm phosphates


More details below if you are interested


Just finished my chlorine treatment for Yellow algae. I cheated after 6 days of OCLT regimen and stopped the treatment when I got to 1.5 to 2 ppm loss at night. Water is clean and clear except for some tiny collection of black (dead algae?) every few days. I am letting the FC levels come down on their own to a normal level and continue to be at 1.5 to 2 ppm loss at night.
I took my pool water to a pool store to check phosphates and they say my phosphates are 2500 and that our city water comes with 200ppm. The pool store "kids" tell me that even if I kill the algae that is in the pool, the high phosphates mean the algae will simply grow back quickly feeding on the phosphates.

 

[AimeeH]

But the algae won't come back in a properly chlorinated pool.

 

[bridgman]

If you follow "pool store rules" for FC level (basically ignoring CYA levels and keeping FC of 1-3 even with high CYA) then algae probably will grow back.

If you follow TFPC rules (know your CYA level and maintain an appropriately high FC level) then it will not.

So they're sorta right and sorta wrong.

 

[mikespoolfl]

If you stop at 1.5 to 2 ppm loss at night it sounds like you still have something going on. Pool stores are not know for thier test accuracy.

 

[cood60]

Yeah, I just found a past forum discussion on a lot of this. Guess I need to do the mustard shock again and be more patient this time

 

[Butterfly]

Just finished my chlorine treatment for Yellow algae. I cheated after 6 days of OCLT regimen and stopped the treatment when I got to 1.5 to 2 ppm loss at night. Water is clean and clear except for some tiny collection of black (dead algae?) every few days. I am letting the FC levels come down on their own to a normal level and continue to be at 1.5 to 2 ppm loss at night.

There is no shortcut for the SLAM process. You simply wasted all that work and chlorine!

Remember, start off with normal shock levels and meet the three criteria to determine that you are done. See red lines in my sig.

Then, do the Mustard Algae kill. Follow the Pool School article to the letter, or as you know, it will come back and bite you.

Don't forget to scrub/clean all the nooks and crannies, pull light fixtures from niches, pull ladders/steps, brush, brush, scrub everything!

 

[cood60]

OCLT confusing school rules?

Just re-read the school rules for testing and am confused. (not sure why I did not see this before)
The OCLT testing process calls for 1 or less reduction in FC levels for overnight testing
The CYA Notes under the CYA section of the extended Test Kit Directions (last paragraph) say "The precision of the measurement is plus or minus one drop when up to 10 drops are used, or plus or minus 10% of the final reading when more than 10 drops are used."
So, when I am at 30ppm for a shock, how will I ever know if the OCLT is good (no algae) since 10% of 60 drops is plus or minus accuracy of 6 drops
which translates to 3 ppm plus or minus?
I am probably misunderstanding the directions, let me know my error
Thanks

 

[cood60]

Yes I was being hasty giving up after 7 days. But, to make an excuse for myself, I was getting frustrated by irregular readings from the night and morning results. Sometimes I would do three FC tests and get results that were 3-5 drops different. Today I decided to re-read the school rules on testing. I posted this on another thread just now but it is pertinent to this thread so here is what further confuses me:
The rules in the Extended Test Kit Directions (last paragraph) say that the precision of the test when testing higher than 10ppm is +/- 10% meaning that when doing SLAM, as I did, I was using 30 ppm levels which means 60 drops of titrant which has an accuracy of +/- 6 drops or 3ppm meaning there is no way I can be sure that the algae has been defeated. Any ideas?

 

[Casey]

Re: OCLT confusing school rules?

I think you are misunderstanding and combining 2 things that aren't suppose to be. The CYA test is a +/-, give or take. That is one separate deal.

The OCLT is that lets say you go to bed with 30ppm FC in the pool. If you wake up to a crystal clear pool, .5CC or less of CC and 29PPM FC in the morning before the sun hits the pool, you, my friend are golden. IF, you go to bed at 30PPM and wake up to 27PPM FC, you are not done SLAM'ing the pool and you keep going.

Hope this makes sense for you.

 

[Casey]

I believe I answered that for you. And, you must not stop a SLAM prematurely, even if you are tired of it as you will have wasted a lot of your time, energy, chlorine and money, only to start all over. Phosphates don't mean SQUAT in a properly chlorinated and maintained pool.

 

[duraleigh]

Re: OCLT confusing school rules?

I am confused that you are posting "CYA" which is completely unrelated to the OCLT. Post back and clarify.

In the future, do not start a new thread....now you have two concurrent threads and it is hard for frequent responders to keep track.

I am putting this back in your original thread.

 

[bridgman]

The rules in the Extended Test Kit Directions (last paragraph) say that the precision of the test when testing higher than 10ppm is +/- 10% meaning that when doing SLAM, as I did, I was using 30 ppm levels which means 60 drops of titrant which has an accuracy of +/- 6 drops or 3ppm meaning there is no way I can be sure that the algae has been defeated. Any ideas?

Fair question. There is an important distinction between *absolute* accuracy (any test kit measuring a reference solution) and test-to-test accuracy for the same kit. The absolute accuracy takes into account manufacturing variations, aging of the reagents, temperature when doing the tests, presence of other stuff in the water etc... so there can be a fairly wide variation (10% is pretty darned good). In your case though, you're using the same kit with the same reagents on the same water under almost the same conditions between evening test and morning test, so nearly all of the factors contributing to the +/- 10% range are not applicable.

 

[cood60]

I am sorry for confusion. I did not mean to say I was referring to CYA section of the Extended test kit directions. I meant to say the FAS-DPD Chlorine Test section. And I see that I have further confused things by saying I was reading from the section in the "Pool School rules". It was actually a forum thread called Extended Test Kit Directions and the section I am referring to is dated 7-18-2010 by JasonLion, last paragraph/sentence says "•The precision of the measurement is plus or minus one drop when up to 10 drops of titrant are used, or plus or minus 10% of the final reading, when more than 10 drops of titrant are used." Is this oor is this not refering to the FAS-DPD FC test ? The one we use when checking any FC level including high levels?

 

[JasonLion]

That statement is correct and applies to the FAS-DPD chlorine test, but as bridgman pointed out it is about absolute accuracy, not about repeatability. The test is repeatable +-1 drop throughout it's entire range. As long as you are using the same reagents, same dropper bottle, same measuring tube the test is very repeatable.

 

[bridgman]

Repeatability. That's the word I was looking for. Thanks !!