Clear, but no chlorine???

[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

[mary jo]

OK - good to know. I will continue on using 1 heaping scoop.
what about the yellow TA reading?

btw: hubby swam in the pool this morning- no skin or eye issues. sides and bottom squeaky clean. he said when you are actually in the water it does smell like a hotel pool.

[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.

[Watermom]

Dave, did you see Ben's post above?

[BigDave]

@Watermom: No I hadn't, thanks for pointing it out - more simul-post.

I stand by my assertion that this is a case where our regular advice of one scoop is enough may be breaking down.

While the sample is too small for statistical scrutiny, mary jo's results are consistent and exceed the error of the test. 2ppm (4 drops) more FC was measured in each session. It's also worth mention that the measured CC was consistently 0.5ppm lower although this is in the error of the test. I am hesitant to ascribe this variance to testing error or bias (despite mary jo's assertion of rookie status) as she has performed these tests more often in the last month than most of us will in a season and that, while not blinded to the test, she wasn't aware of the expected outcome.

I think this is important as we start to guide people to HiC2 operation. 30ppm FC is beyond the limit of the test and Taylor suggests adding more DPD powder to accomodate.

[BigDave]

... he said when you are actually in the water it does smell like a hotel pool.

When swimmers are in a high chlorine pool, the chlorine will get to work on skin oils, lotions, swim suits, etc. and will produce that too-familiar smell directly on the swimmer.

[mary jo]

OK- one thing I have learned is to order extra testing supplies, so while I am going through my DPD at a rapid pace, I have already ordered another one (i love amazon prime) so 2 scoops is fine.

on a related note: i wanted to ask about the plastic testing vial (Taylor gives it a strange name…I was reviewing their testing vid's last night). Just noticed a film inside the vial (i typically rinse,shake, air dry). I used dish soap today to clean it. Is this OK? (no info on vial cleaning anywhere)...

[CarlD]

OK- one thing I have learned is to order extra testing supplies, so while I am going through my DPD at a rapid pace, I have already ordered another one (i love amazon prime) so 2 scoops is fine.

on a related note: i wanted to ask about the plastic testing vial (Taylor gives it a strange name…I was reviewing their testing vid's last night). Just noticed a film inside the vial (i typically rinse,shake, air dry). I used dish soap today to clean it. Is this OK? (no info on vial cleaning anywhere)...

Yeah, keeping extra reagent is wise.

That black stuff doesn't seem to affect anything.

[BigDave]

Rinse it until all the soap is gone.