Disappearing CYA

[aylad]

Glad it's starting to clear up for you. If you add your chlorine at night, then retest in the morning before the sun has a chance to hit the pool, you'll have a more accurate idea of whether your chlorine is holding or not. Keep brushing daily, and keep your filter running to get all the dead algae out.

Oh, and sorry about the gender mixup--somehow, in reading your username, it stuck in my mind as "Virginia". Sorry!!

Janet

[vinnygnj]

Thanks for all the help!

This morning I tested the water and it appeared to be above 5 PPM. I didn't have time to dilute the sample but I was happy to see it high.

I came home today and took a sample and again it was reading 5 PPM. I was able to dilute the sample to 1/2 and it was between 2 and 3 PPM. I think the algea is dead as the sun was shining all day.

I have been brushing and couldn't understand why the algea kept coming back. After taking a few weeks of readings in the beginning of the season and having the same readings I do things automatically and was putting chlorine in at night assuming that it was lasting until the next day. I guess it's never too late to learn something!

Thanks again!

Vinny

PS: I really wasn't upset about the she thing.

[mbar]

You need to get your chlorine up to shock level, and hold it there for a couple of days or you will be fighting algae for the rest of the summer. You can tell the algae is gone if you hold Free Chlorine overnight. There should not be any combined chlorine. I would suggest you invest in a good test kit - one that can test over 5ppms of chlorine. It will be the one of the best investments you can make.

[vinnygnj]

I would think that after adding the chlorine yesterday afternoon with the sun off the pool and having it in the sun all day today (7 AM to 3 PM) with low stabilizer (35 max) and getting a reading of 5 - the algea is pretty much gone (maybe not). If I remember correctly 10 PPM stabilizer is supposed to protect 1 PPM chlorine so 35 PPM would protect 3.5 PPM chlorine and the chlorine was over that.

I've been adding bleach since Saturday at high levels a few times a day and it hasn't dropped below 5. I don't have any visible signs of algea unlike other days. If algea is present wouldn't my chlorine would have been used up by now (see 1st paragraph) or at least showing low. My pool is not smelling like chlorine and when I tested for CC on Sat after putting chlorine in at night it didn't register any.

I am going to test the pool in the AM and see what the reading is and if it does drop below 5 I will add more chlorine, heck I'll just add more chlorine anyway.

Not much difference in a Taylor K-2005 and a Taylor K-2006, I can measure high levels of chlorine by halving the pool's water and multiplying the reading by 2 or if higher 1/3 and x3.

Please let me know if what I said makes sense.

Thanks!

[mbar]

I am going by Ben's "best guess chart". While the cya would protect 3.5 ppms of chlorine, it is not enough to kill all of the algae. The shock level for a cya of 35 would be 15ppms. My understanding of this chart is taking it up to 5 would not be enough to kill all the algae. It would keep it under control for a while, but not kill it all at one time will cause you trouble any time your chlorine is low. I know that when I start to have problems holding onto chlorine, I don't always have cc, or the smell of chlorine right away. I have found it easier to deal with it at the first sign by taking my chlorine up to shock and leaving it there until the chlorine holds overnight. In my opinion you are right on the border of controling the algae bloom. You have enough chlorine in the water to keep killing algae, just not enough to kill all of it.When I was battling my swamp in the beginning of the season, I didn't smell anything in my pool, but the chlorine was still being used up overnignt. It did use less and less as time went by, but it did take a while. I am only giving you my suggestions based on what I have experienced. It is up to you to do what you think is best.

[waterbear]

Not much difference in a Taylor K-2005 and a Taylor K-2006, I can measure high levels of chlorine by halving the pool's water and multiplying the reading by 2 or if higher 1/3 and x3.

Please let me know if what I said makes sense.

Thanks!

Actually, there is a HUGE difference in DPD and FAS-DPD testing. First, it has been found that about 4 out of 5 men have difficulty in differentiating the red colors on a DPD test (women do not have this problem) and second, dilution decreases your precision on the test so the FAS-DPD test is much more precise (down to .2 ppm!) compated to doing dilutions with the DPD test. The K-2005 does include dilution marks on the tester for 1:1 dilitions (multiply results by 2) and 1:4 dilutions (multiply results by 5) but these are only really going to give you more of a ballpark figure while the K-2006 will give you results that are precise to either .2 or .5 ppm depending on the size of your testing sample. (I have both kits, among others).

Also, FAS-DPD testing directly measures CC instead of measuring TC and then having to subtract the FC from the reading.

[vinnygnj]

mbar,

I guess I actually didn't ask any questions, I was just thinking out loud. I don't have a very big outbreak of algea and luckily my pool didn't get away from me.

If my chlorine didn't disappear to 0 or very low, hasn't the algea been killed? When you were fighting the algea battle where you losing only a small amount of chlorine at night or most of it? I have fought with it and have had no chlorine by morning - that's why I ask.

Since the chlorine didn't go below 3 and my stabilizer is probably around 35, isn't all my chlorine above 3 killing anything it can? I put enough chlorine to last a night and a day of sunshine.

I know of 2 reasons for shocking a pool 1) breakpoint chlorination which I know isn't practiced here and 2) put enough chlorine into the water to kill the organisms and make sure there is enough chlorine left over so that you're assured a kill (and yes it might take days to accomplish that kill if chlorine gets too low). Why go to 15? Is there something else I'm missing?

waterbear,

I understand the color thing and yes at times I can't tell the difference between 1, 1.5 or 2. But I usually can tell the difference between 2, 3 and 5. Maybe other men can't and maybe as I get older I will lose this ability so I will have to go to the K-2006.

As far as the precision of the testing, why do you need to be that precise?

I know that that as CYA rises you need to add more chlorine but is there really a difference between 5 PPM and 5.5 PPM at a CYA of 30 or 100. I would think that if you were close to a important level that you just add more chlorine for a safe measure. If I almost halved the water and I almost got to a reading of 3, well I'm about 6 - I don't see a problem unless you wanted to precisely add enough chlorine for breakpoint chlorination but like I said - add more than just enough.

With CC, I thought that the only time you test it is when you lose large amounts of chlorine and you need to break the CC before it starts smelling? I was under the impression that the belief here is that sunlight destroys the CC. I typically don't test for CC in the pool after Ben stated that and whenever I have I had none.

[mbar]

Owww, my head hurts I will leave this to the chemistry pros, like waterbear and chemgeek. All I know is that whenever I lose chlorine overnight, it is because it is fighting something. If you lose a few ppms it is ok when the water starts at shock. I just think you are asking for trouble when you are playing around with such small numbers as 1ppm to 3ppms to do the work. Just as you said, it is not precise, therefore I would take it to shock and keep it there until the chlorine seems to be holding. You can tell with your own pool, as everyone's pool is different. So you can do as you like, but why are you so adverse about shocking the pool? If you are just after the reasons why shocking is needed, then I will leave it to the chemistry pros

[waterbear]

Since the chlorine didn't go below 3 and my stabilizer is probably around 35, isn't all my chlorine above 3 killing anything it can? I put enough chlorine to last a night and a day of sunshine.
Algae is harder to kill than bacteria and 3 ppm FC is the MINIMUN for a CYA above 30 ppm (but less than 50 ppm). It often takes a higher level to keep algae at bay.
I know of 2 reasons for shocking a pool 1) breakpoint chlorination which I know isn't practiced here and 2) put enough chlorine into the water to kill the organisms and make sure there is enough chlorine left over so that you're assured a kill (and yes it might take days to accomplish that kill if chlorine gets too low). Why go to 15? Is there something else I'm missing?
I don't know why you have the impression that breakpoint chlorination is not practiced here. Breakpoint means adding enough chlorine to destroy any CC in the water. The formual for breakpoint (10x the CC level) does not always hold true and that is what is usually said but the actual process of reaching breakpoint is what is talked about when people are told to shock to destroy CC.
waterbear,

I understand the color thing and yes at times I can't tell the difference between 1, 1.5 or 2. But I usually can tell the difference between 2, 3 and 5. Maybe other men can't and maybe as I get older I will lose this ability so I will have to go to the K-2006.

As far as the precision of the testing, why do you need to be that precise?
Well, since it's usually recommened to 'shock' when the CC is greater than .5 ppm and you yourself said that you cannot differentiate tha small an increment with the DPD test I think that answers your question.
I know that that as CYA rises you need to add more chlorine but is there really a difference between 5 PPM and 5.5 PPM at a CYA of 30 or 100.
At a CYA of 100, no. At a CYA of 30, possibly.


With CC, I thought that the only time you test it is when you lose large amounts of chlorine and you need to break the CC before it starts smelling? I was under the impression that the belief here is that sunlight destroys the CC. I typically don't test for CC in the pool after Ben stated that and whenever I have I had none.

According to the precision of your testing which you have stated is 1 ppm or greater!