Clear, but no chlorine???

[mary jo]

A big thank you to FormerBromineUser- yesterday I got a "house call" from her to look at my pool - an extra pair of eyes might help. Everything that could be cleaned was cleaned EXCEPT----when I turned the in-line chlorinator OFF several weeks ago, I forgot to take the pucks out! Luckily FBU caught this and the petrified pucks (about 6 of them) were removed and the empty tower cleaned (with hose water). There was a rust-colored looking stain on the tower walls, a bit of sediment on the bottom, so I soaked it w/ hose water and sprayed it out w/ the hose on jet spray setting. It does look much cleaner and water in it is clear, so I turned it on just a bit to let water trickle thru it- there's no shut off value for the chlorinator and Nature2 unit (which are located next to each other on their own line).
Not sure if that was a contributing factor, but it's now empty and clean.

Numbers:
Yesterday FC went from 30 to 27 (dawn to late afternoon) so I added about 1/2 jug of bleach.

Last night tested @ 8:30pm FC=30 CC=2.0
This morning tested @ 7:15am FC=29 CC=2.5

I didn't get to the brushing yesterday- will do it today.

[BigDave]

Sounds good, 0.5ppm is the error in the test so those readings are pretty much the same. Have you had any sun?
I'd like to try a little experiment If you'll indulge me. For the next FC/CC test, use two dippers of DPD powder. Post any observation you have about the test.

[mary jo]

Yes, we had lots of sun yesterday, and today as well (so far). Should I do the 2 scoops when I test this afternoon or wait until this evening?

Also, a question: my husband is coming back in town and has already asked me if he can swim tonight. I now know (and now he knows) it's safe to swim @ FC30, but will it mess up the FC/CC levels if he does? I'd rather wait until we're in the clear- POP, right- but wanted your opinion on whether this would set us back any.

[BigDave]

Go ahead and swim - in an old suit. Next time you test, I'm curious if you'll see a difference at 30ppm FC.

[FormerBromineUser]

Just sterilize the hubby before he jumps in!

[mary jo]

It rained last night, so hubby is going in the pool this morning (after playing tennis). I'll suggest he rinse off beforehand.

OK- BigDave- I must admit when you mentioned experimenting with 2 scoops of DPD my first thought was: hmm, you are testing for possible user error, which, given my # of rookie mistakes I'd say makes sense… but it turns out i DID get different results.

Yesterday's testing (8-28) The pool's numbers @ opening: FC=29 CC=2.5 Brushed the pool.

I ran FC/CC tests @ 4:00pm, 10ml sample, added my standard "1 heaping scoop" (because heaping is my standard), and got: FC= 25. CC=3.0

Same test w/ 2 scoops: FC=27. CC= 2.5
Then I tried 3 scoops: FC=31. CC=2
THEN I tried 1/2 scoop: sample "flashed" pink and then went clear again.

Hmmm- added a jug of bleach to the pool and waited several hours.....

Yesterday evening @ 8:30pm I tested using 1 and 2 scoops to see what would happen:
1 scoop: FC =30. CC=3.0
2 scoops: FC=32. CC=2.5
Did 2 scoops again: FC=32. CC= 2.5

This morning- tested @ 7am:
1 scoop FC=30 CC=2.5
2 scoops FC=32 CC=2

what's going on- or am I just an erratic tester?

also: just tested TA and pH: pH off the chart (but you mentioned this would happen w/ high FC), but
TA went from green to blue to pale yellow (after 14 drops). ???

[PoolDoc]

THIS is normal random variation in test results.

Same test w/ 2 scoops: FC=27. CC= 2.5
Then I tried 3 scoops: FC=31. CC=2

HIGH chlorine bleaches out low levels of DPD; this is ALSO a typical result.

THEN I tried 1/2 scoop: sample "flashed" pink and then went clear again.

THESE are also normal random variation in test results; statistically speaking, they are identical results.

Yesterday evening @ 8:30pm
1 scoop: FC =30. CC=3.0
2 scoops: FC=32. CC=2.5
Did 2 scoops again: FC=32. CC= 2.5

This morning- tested @ 7am:
1 scoop FC=30 CC=2.5
2 scoops FC=32 CC=2

[BigDave]

Erratic tester, nope, your results are consistent. The second scoop can make the endpoint more clearly defined and at the comparatively high chlorine level you have, I wanted to see if insufficient DPD might be influencing the test. Apparently it is. I think it's best to maintain the shock level a bit longer as yesterday's chlorine loss was about 5ppm and (by any measure) the pool still has significant CC. Can you supply of DPD powder survive 2-scoop testing? Morning and evening is plenty often enough testing now.