CH "fading endpoint"

[d1mbu1b]

Hello, and thank you for letting me participate in your forum.
I have been scouring and learning as much as I can; but ran into a stumbling point.
This site has been an awesome resource.
I am very grateful for all the information being shared.

I am a new first time pool owner as of June 2010.
I recently learned the "too much CYA lesson" the hard way with a mustard algae bloom after a sustained hard rain.
At this point I realized, sadly, that relying on the pool stores to do my testing and was not an option for me.

I have the "trouble free test kit" TF-100 and have the following results.
Water is crystal clear with no visible signs of algae anymore.
FC 30
CC 0
TC 30 - Is this right?
pH 7.5
TA 110
CH ?
CYA 90
temp 75

1) CH test - 'fading endpoint'
Please help me determine how to get a result for the CH test.
I tried the conventional per instructions.
I tried adding two drops of R-0012 prior to adding R-0011 per TF-100.
I tried adding 5 drops of R-0012 first per http://www.taylortechnologies.com/Chemi ... ntentID=70
I was not able to get a result after 60 drops over 4 tests.
I figure I should quit and ask before I ran out of drops.
Previous pool store tests show 450ppm but I am weary of there results.
Why Is the 20 drop bottle of R-0010 so small?
Is there a way to test for the metals? If so, Is there a way to remove them?

2) CH treatment
Since I cannot remove (can i?) CH (I have well water) is there anything I should be concerned with?
If so what and how.

3) TA
Please help me determine my target TA based on my high CYA.
Should it be 130; 130-CYA/3=100?

4) CYA
I am going to try and wait out the CYA over the "winter" here in Melbourne Florida.
Draining does not seems practical for me
I have not been able to find a "mobile reverse osmosis plant" nearby.
Any pointers will be appreciated.
I have quite the tri-chlor tabs cold turkey for now.
I have a big ol' bucket-o-tabs $$$ the pool store 'sold' me.

5) FC
At what point is it safe for my children to enter the water?
I recently shocked based on the pool calculator recommendation for CYA of 80ppm and It has not been sunny the last few days

Thank you again.

 

[chem geek]

Welcome to TFP! Answers to your questions are below.

FC 30
CC 0
TC 30 - Is this right?
pH 7.5
TA 110
CH ?
CYA 90
temp 75

Yes, the Total Chlorine (TC) = Free Chlorine (FC) + Combined Chlorine (CC). However, you shouldn't worry about TC. Just focus on FC being appropriate for the CYA level and on CC being near 0 (<= 0.5 and usually <= 0.2).

1) CH test - 'fading endpoint'
Please help me determine how to get a result for the CH test.
I tried the conventional per instructions.
I tried adding two drops of R-0012 prior to adding R-0011 per TF-100.
I tried adding 5 drops of R-0012 first per http://www.taylortechnologies.com/Chemi ... ntentID=70
I was not able to get a result after 60 drops over 4 tests.
I figure I should quit and ask before I ran out of drops.
Previous pool store tests show 450ppm but I am weary of there results.
Why Is the 20 drop bottle of R-0010 so small?
Is there a way to test for the metals? If so, Is there a way to remove them?

If you expect the CH to be high, you can save on titrant drops by using a 10 ml sample where each titrant drop represents 25 ppm (instead of 10 ppm with a 25 ml sample size). It's possible you have extraordinarily high CH as you say you are on well water. The pool store CH tests can have problems measuring very high CH so try the 10 ml sample size approach -- even 1000 ppm CH will be 40 drops which is less than what you are using.

2) CH treatment
Since I cannot remove (can i?) CH (I have well water) is there anything I should be concerned with?
If so what and how.

The concern would be with scaling of the water. You should do tests of your well water directly, not only CH (use the 10 ml sample size as noted above), but also TA and pH. You can live with very high CH by maintaining a lower TA level and not letting the pH get too high.

3) TA
Please help me determine my target TA based on my high CYA.
Should it be 130; 130-CYA/3=100?

If your CH is truly very high, you'll want your TA to be low. How low depends on what you get for your true CH, but let's say that it's something extraordinarily high like 1000 ppm. With your 90 ppm CYA, you could get into balance with a TA of 65 ppm (assuming a pH of 7.5). So this is not unmanageable, at least at first. The problem will be with evaporation and refill which will continue to increase your CH level and also make maintaining a lower TA difficult (assuming the TA isn't very low in the well water).

4) CYA
I am going to try and wait out the CYA over the "winter" here in Melbourne Florida.
Draining does not seems practical for me
I have not been able to find a "mobile reverse osmosis plant" nearby.
Any pointers will be appreciated.
I have quite the tri-chlor tabs cold turkey for now.
I have a big ol' bucket-o-tabs $$$ the pool store 'sold' me.

That's fine. Just maintain an appropriately higher FC level -- a minimum of 7 ppm when your CYA is at 90 ppm.

5) FC
At what point is it safe for my children to enter the water?
I recently shocked based on the pool calculator recommendation for CYA of 80ppm and It has not been sunny the last few days

Your current FC of 30 ppm with a CYA of 90 ppm has the same active chlorine (hypochlorous acid) concentration as a pool with 0.5 ppm FC and no CYA. So it's less reactive than most indoor pools that don't use CYA. However, the high FC level means you don't want to ingest large quantities of water. If your kids are regular gulpers, especially if they tend to swallow down their windpipe and get water into their lungs, then you might want to wait (even at normal chlorine levels, you want to avoid gulping pool water into the lungs). Otherwise, swimming is OK, especially if you don't notice any strong or bad smell (and you shouldn't given the zero CC). You will likely smell a faint "fresh" chlorine smell since the chlorine level is about 4 times higher than the normal minimum for this CYA level.

Richard

 

[mas985]

I also have a fading end point problem so I can relate. Based upon our water reports, I believe that mine is due to magnesium in the water since it has tiny red dots floating through the blue solution at end point. A couple things that I have found is that if I use the 10 ml instead of the 25 ml line it actually makes it harder to determine the end point. Also, focusing on the small red dots, assuming that is your problem as well, can lead you to adding way to much titrate. The key for me was to keep the vial at arms length and focus on the water in between the red dots. The solution goes from red to purple to bluish purple to blue but at the end point the red tiny dots are still in solution. Also, adding more of the indicator seems to help some as well as it makes the end point a bit more dramatic.

 

[chem geek]

I suppose this all depends on whether you are actually seeing a "fading endpoint" which has the floaties that Mark describes or where it changes color but then switches back vs. you simply have a very high CH level and aren't seeing anything strange going on (i.e. it stays a fairly constant reddish color with no floaties or temporary changes to blue). It wasn't clear from your description what you are actually seeing -- you said "fading endpoint", but is it just that you never got to an endpoint? Do you see the floaties (precipitate particles) Mark describes?

 

[d1mbu1b]

WOW, thank you very much.
I will try the recommendations and report back.

I see the mixture turning clear.
but there are some maroon swirlies and maybe floaties before that.
When I test again I will try to be more descriptive.
I am ignorant to all this so I really don't know what to look for.

Is there a way 'chemically' to test the volume of my pool?
It is a highly irregular shape.
My 11000 gallon is a rough estimate based on 1) ballpark dimensions, 2)getting expected results after adding baking soda and/or acid, and 3) timing the fill and fill rate.
Unfortunately, I have no confidence in any of these.

Thanks again

 

[mas985]

The solution turns clear? Do mean there is no color at all or did you mean it goes to clear blue?

It should be clear red at the start and go to clear blue at end and it should not be cloudy other than the small dots I described earlier. Also, you should be swirling the mixture with each drop.

 

[d1mbu1b]

The solution turns clear? Do mean there is no color at all or did you mean it goes to clear blue?

It turns colorless like water.
I will try again when I can break from work.
I probably screwed up the test.

 

[mas985]

With a FC at 30, it could be bleaching out the indicator so try a few drops more of the indicator until you get a stable color or just wait until the FC drops before trying the test.

 

[Bama Rambler]

Once you get the testing stuff figured out and become old hat at it, then you can use chemical additions to hone in on the pool volume. I.E. it'll take a certain amount of 6% bleach to raise a certain amount of water a certain number of ppm. The Pool Calc is the best tool to use for figuring that out. However, that's something to work on AFTER you've gotten comfortable with the testing.

 

[chem geek]

With a FC at 30, it could be bleaching out the indicator so try a few drops more of the indicator until you get a stable color or just wait until the FC drops before trying the test.

If the high FC is what is bleaching out the indicator, you could add some drops (say, 5 drops for a 25 ml sample, 2 drops for a 10 ml sample) of sodium thiosulfate (R-0007 from the TA test) first before adding anything else in the CH test. I can't guarantee that thiosulfate doesn't interfere with the CH test, but I don't believe it does.

 

[d1mbu1b]

I did the 25/10 ml swap for CH, hopefully correctly as follows:
20 drops R-0010 and swirl
5 drops R-0011L and swirl
at this point it was a transparent/clear 'more maroon than red' red
then one at a time with swirling and wet wiping between for 20 drops or R-0012 until it turned a transparent shade of violet not blue.
Is this something similar to the FC test turning yellow ?
Does this equate to 500 ppm CH?
Did I perform a valid test?

Here are some pictures of the water as of 3:30 Eastern time today:
http://s1085.photobucket.com/albums/j43 ... 06%20pool/
What is this stuff?
It is slimy and dusty and mustard brown.

I do appreciate the help.

 

[chem geek]

I should have told you to scale down the calcium buffer to 8 drops and the indicator dye to 2 drops though more indicator dye isn't a problem. Probably having more calcium buffer doesn't hurt either.

Anyway, the purple is probably your endpoint since it seems the color is so weak for whatever reason. If you added some titrant drops first, that might make a sharper (hopefully bluer) endpoint. It does seem like your CH might be on the order of 500 ppm.

You could also test your fill (well) water and shouldn't have any interference problems from a high FC. I'll bet you get a similar result. 500 ppm CH is manageable as I had mentioned above, but will require you to lower the TA which is a bit of a pain (the procedure is described in Lowering Total Alkalinity).

If the mustard stuff in your photos was like dust, then that could be yellow/mustard algae, but it sounds like it's more stuck to the surface, correct? Otherwise you'd have a hard time feeling it to describe it as slimy. Though it sounds like algae, it could also be pollen if it's "squishy". If you have a microscope, you can look at it and tell for sure since pollen is solid and often spiky while algae is semi-transluscent and usually doesn't have spikes and is often oblong. With the high shock levels of chlorine, if this were algae it would more likely have turned gray.