Which results are right?

[KirstenHW]

I am a long-time BBB follower with a Taylor K-2006 kit & a Rainbow 2n1 daily kit (with new Hydrotools reagents). Taylor reagents are from 2 years ago, never stored in extreme heat or cold, religiously tightly capped.

I apologize in advance for the length of this post - I am trying to provide a chemistry history.

Pool is 18x36 vinyl IG, 1 hp hayward Super pump, Hayward EC-65 DE filter, 2 returns, 2 skimmers, 1 wall vac line.

At opening 5/12/06, water was clear, ahd a minor patch of algae on floor under site of mesh panel on solid safety cover.

My initial numbers with Taylor kit at opening 5/12/06 were:
FC=0.5
CC=0
pH=7.1
Alk=75
Calc=100
CYA<30 (couldn't tell exact)

I added 3 pucks of trichlor ea to my 3 Rainbow floaters fully open and a 4 lb box Borax.

Test results 5/18:
FC=0
CC=0
pH=7.2
Alk=75
Calc=75
CYA<30

Then we were away the weekend of 5/20, so no serious work done to it.

On 5/28 I pulled out the big guns: Added sixteen 3-quart bottles of bleach, plus two 1-gal/46 oz bottles bleach.

Test results next morning on 5/29:
FC=24.5
CC=1
TC=25.5
pH=7 (base demand=1 drop=18.5 oz borax)
Alk=100
Calc=80
CYA<30

However, my Taylor kit was saying my pH was 7, Rainbow 8.5. So as a test, I had 2 pool stores do their testing. Store #1 with a test strip agreed with my Taylor #s, Store #2 with their "computer" testing got:
FC=5
CC=0
TC=5
pH=7.7
Alk=61
Calc=88
CYA=8
TDS=400
Sat Index= -0.45 = corrosive (Isn't a "high" pH basic, not corrosive??)

I went home, added nothing, then in the afternoon I retested and got:
FC=13.5
CC=.5
TC=14
pH=7.1
(I didn't bother w/ Alk, Calc or CYA)

That evening I added 1 lb. of Borax. Filters been running constantly, water is very clear, vacing-brushing-regenerating EC-65 filter.

This morning 5/30/06, my mom - who runs a water treatment lab - tested the water and got these #s (she can't test for alk, calc or cya). She said the pool & sample smelled very strong of chlorine (I cannot smell it - I am having problems with my sense of smell & taste):

FC=9.6
CC=10.8
TC=20.4
pH=7.5

I tested as well and got:
FC=10
CC= 0.5
TC=10.5
pH=7.3 (Taylor kit has a yellow cast - hard to tell if 7 or 7.4; Mini kit = 7.7 - much more red looking)
Alk=80
Calc=70
CYA = less than 30 (filled to the very top of the tube the dot is not visible - don't know what the number is - it is above the 30 line)

Which results do I go by?
I have no more algae, do I still keep shocking?
Should I replace the reagents before I do anything else to the pool?
I am embarrassed that I am asking all this, as I have been a loyal follower of this site for years and never questioned the chemistry before. I am a little frustrated. Pool is clean, needs a final vac of dead algae (minimal).

I'd like to post photos, but don't know how.

THANK YOU for all your patience and in advance for your advice!

[PatL34]

The main thing I see that the CYA is low. Need to get that up to 40-50 ppm.

The CC has dropped, and that's through all the bleach you have been adding. A+

I would defintely go to the pool store and replace all your reagents.

Hope this helps.

Pat

[waterbear]

just to comment on your pH test. pH cannot accurately be done with high chlorine levels because it actually converts some or all of the phenol red indicator to chlorophenol red which tests for a much lower ph range (4.6 to 6.8). If your chlorine levels are high and your pH is testing high or off scall all you really know is that your pH is above 6.8! The taylor reagent for pH (and some others but not all) have a chlorine neutralizer built in that will work up to about 15 ppm chlorine. The only way to get an accurate test with high chlorine levels is with a properly calibrated pH meter or wait for the levels to drop and then test pH. The taylor is giving you more accurate results than your mini kit because of the reagent.
As far as your different results from the pool stores on FC and CC... DPD tests that many pool stores use can and will bleach out at levels of FC above about 10 ppm. FAS-DPD tests such as in the K-2006 do not have this problem until chlorine levels get very high. Some test strips will bleach out,some won't ....depends on the chemistries they are using in their reagents.

I would believe the results of FAS-DPD titration tests for chlorine and would believe the Taylor pH reagent as being the most accurate when the chlorine levels are high although it will still read higher than the actual pH until the levels of chlorine drop to below 15 ppm.


As far as the ALK results, these can vary a bit with Ph and some of the computer softeware makes this correction. IF the pH results are not accurate because of the interferance the calcualtions will be wrong. There is also an 'adjusted ALK' reading that many software programs give that compensates for the amount of CYA in the water and the pH of the water. This can introduce even more error if the pH results are bogus becuase of the chlorine interference.
Hope this helps clear things up a bit.

[KirstenHW]

Thank you Pat & waterbear - a couple more questions:

Will adding CYA stop the "shock" action? I think I am ok now - no more algae on walls or bottom. I'd like to notch back down to normal operating Chl levels. I had probs with too much CYA last year - I am nervous about it this year, as the trichlor pucks are my daily dosing method. If I am not to fear the CYA, what is the min amt I should put in to the pool? None of the pool stores in my area have ever carried the Taylor reagents - any suggestions? I know I can order them from Ben but I am not sure how long it will take being the busy season. With the mini kit, does it matter whose reagents I use so long as they are fresh?

Waterbear, I appreciate the pH-bleaching-out explanation. I thought I recalled it being something to consider and I even added sodium thio to the pH test to see if that would change things. I believe I am ready to maintain the chl at normal levels. If that is the case and I add the CYA as above, once the CHL comes down should I then reassess the true pH situation?

Any ideas on why my mom the lab director's test had such different readings from mine - tests taken within an hour of each other?

And just as an aside, with my vinyl pool I don't ever need to worry about the calcium levels at all, right?

[waterbear]

Thank you Pat & waterbear - a couple more questions:

Will adding CYA stop the "shock" action?

You just need to shock at levels appriate for your CYA See this post
http://www.poolforum.com/pf2/showthread.php?t=365

I had probs with too much CYA last year - I am nervous about it this year, as the trichlor pucks are my daily dosing method. If I am not to fear the CYA, what is the min amt I should put in to the pool?
If you are going to continue using trichlor I would not add any more than enough to get you to 20 ppm and let the trichlor add the rest....or not add any and suppliment the trichlor with bleach to maintain your FC until you get at least 20-30 ppm cya in the water.
None of the pool stores in my area have ever carried the Taylor reagents - any suggestions?
You can order them directly from Taylor by phone or on the web.
I know I can order them from Ben but I am not sure how long it will take being the busy season.
Ben's kit is more economical than Taylor's....more 'bang for your buck' I highly recommend it!
With the mini kit, does it matter whose reagents I use so long as they are fresh?
For OTO probably not, for pH...some of the cheaper ones are not stabized against high chlorine levels, as you have seen.
Waterbear, I appreciate the pH-bleaching-out explanation. I thought I recalled it being something to consider and I even added sodium thio to the pH test to see if that would change things.
That works to a point and is what companies like Taylor put into the phenol red but it can also cause a false high pH reading if too much is used!
I believe I am ready to maintain the chl at normal levels. If that is the case and I add the CYA as above, once the CHL comes down should I then reassess the true pH situation?
Check your pH once the CL is below 10 ppm to get a true reading with the taylor kit.
Any ideas on why my mom the lab director's test had such different readings from mine - tests taken within an hour of each other?
The pH is pretty close. Did they use a pH meter or reagents? The FC reading is basically identical. Only reason off the top of my head for the difference in CC is that your reagents are two years old and taylor recommends replacing them yearly. There ARE other tests for Cl besides OTO, DPD and FAS-DPD. Perhaps they used a diferent test that is more accurate at higher clorine levels. The very high chlorine smell that your mom reported could very well indicate the presence of a high level of CC.
And just as an aside, with my vinyl pool I don't ever need to worry about the calcium levels at all, right?
Not unless you have a heater or grouted tilework anywhere in the pool.

Hope this is helpful!