chlorine test inconsistancies

Jump to latest Follow Reply
R

rotenka

0
Aug 19, 2013
94
Mansfield, Texas
I have been slamming my pool since Friday and have dumped almost 12 gallons of 8.25% bleach in the pool. I have noticed inconsistencies in my FC tests. Just tonight I took two measurements about 10 minutes apart and got a reading 2ppm higher the second time.

I am extremely careful about holding the bottle the same and getting all the drops to be the sane size. Not sure what to do next.
 
2ppm isn't too bad but I usually don't have discrepancies like that. Just confirm that this is taken from the same water sample and using the same test method and reagents. I noticed you are using two different test kits in your sig...

What kind of FC numbers are talking about here?
 
I am only checking FC and CC with the TFT powder and reagent.

I took the first sample just a little over an hour after I added chlorine and I took the second one about 10 minutes after that.

This morning I took three readings. The first two were out of the same bottle, drawn from the pool at the same time and the differed by 2.5 PPM. Then I took a sample with the test tube directly from the pool and it was 3 ppm higher. The third one actually indicated a .5 ppm difference from my measurement last night so I am calling the slam process complete. I will however do another overnight test tonight to confirm.

Measurements last night about 10 minutes apart were 23.5 and 25.5.

Measurements this morning 21 and 23.5 taken from the same sample and then 25 taken directly from the pool.

CC for all of these was at .5 or lower.

All of these were taken with brand new reagents and powder I just got from TFT on Monday.
 
I wish I could provide a definitive answer for you. I can perform that test within .5 ppm consistently but I have been doing it for almost nine years and I think that may be the difference.

The endpoint of the test is when you add a drop and there is NO further color change.....then you subtract that drop.

Are you getting to that endpoint each time?
 
How rapidly are you adding drops? Ideally you let the drops form slowly at the tip of the bottle until the weight overcomes the surface tension, typically about 1 drop per second, with the bottle held perfectly vertically. Any faster than that, or if the bottle is not vertical, your drops can vary in size significantly.

I usually do about 1 drop every 2/3 of a second, and I get consistent numbers. But with the viscous reagents (the dark ones for the TA and CH tests), it takes me closer to 2 seconds to form a consistently-sized drop.
 
I suspect that the chlorine added to the pool has not mixed completely. Is circulation good in the pool? Are you adding via the skimmer (slowly) or by mixing with water in a bucket and pouring around the pool or by pouring near a return? I would expect that in the short run each of these might give different test results depending on your circulation patterns in the pool.

I'd guess that best of all would be a few good sweeps with a Wall Whale brush after chemical additions for I observe that this is one heck of a mixer.
 
TomBorg said:
But with the viscous reagents (the dark ones for the TA and CH tests), it takes me closer to 2 seconds to form a consistently-sized drop.
Click to expand...
Drop size does not matter for these 2 reagents (green for TA and purple for CH). In fact you can use more or less drops to see the colors better. Actually the same is true for the pH test as well.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Could be the rate of my drops. I will try to be more consistent and see what happens. I do hold the bottle vertical typically the first few drops don't come out as slow as the rest. I guess I could waste a few until the air in the bottle stabilizes.

I have left the sample sitting after finishing a couple of times. Why is this important?
 
I would ensure you are pulling samples from the same location and depth each time. Plunge the rinsed sample bottle, cap off, upside down to elbow depth and turn it upright to fill completely.

I had some difficulties with consistency when I first started doing my own testing, doubting my drop size, trying to figure out the best swirl/mix technique, etc. Seemed like I needed three hands and someone to count for me. I purchased a speed stir about three weeks into it and was amazed at how easy testing became. I could never go back to hand mixing for the tests.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply