I got cocky - It bit me in the seat

[rdy2fly]

So, this is the first summer we've had a pool. Thanks to TFP, we have enjoyed a sparkling clear pool all summer. Fortunately I researched TFP prior to getting a pool, so I've never been "pool stored". I felt like I had this down, and almost on auto pilot. Having a SWG, I was down to just testing the water weekly. Last Saturday, due to storms and very heavy rain I had to drain some of the pool as it was overflowing. After doing so, I tested the water, and found I needed to increase CYA from 60 to 80, and my salt was a little low too. So I added the CYA to bring it back up to 80 and 1/2 bag of salt to bring that up as well. My FC on Saturday was 9.5 (according to pool math my minimum is 4 and target is 11) and water temp was 86. The water was a little chilly to our liking since the nights are getting coolr, so we put the solar cover on and it sat for 3 days untouched, but the SWG and pump was set to run the normal amount of time.
Tuesday night we decided to get in the pool as the water temp was up to 92 (bath water!!) But when we pulled the cover off it was obvious something was wrong. The water was very cloudy and had a little bit of a green tint to it. I ran my tests, and FC was 4.5 and CC was 0. Since the cover was on for 3 days, and SWG was running, there shouldn't have been such a drop in FC. So I immediately threw in a jug of bleach, waited a while and tested again (FC now at 20).
Checked the water the next morning and green tint was gone but still very cloudy. FC down to 17, CC at .5 so I decided to SLAM. Got FC up a little too high to 33.5 (Pool math showed 31).

Here is my question for you fine people:

According to the Extended Test Kit Directions "The precision of the measurement is plus or minus one drop when up to 10 drops of titrant are used, or plus or minus 10% of the final reading, when more than 10 drops of titrant are used."
Since my SLAM level is 31, that means that to measure I am putting in 62 drops. 10% of 31 is 3.1, but when I do an OCLT I can't have lost more than 2ppm. This morning i had lost 2.5, which is obviously more than 2, but still within the 10% variance given the high FC. Hopefully I'm making sense! I'm just not sure whether 2.5 is acceptable or not.

As of right now, the water is still very cloudy. I am running pump 24/7, and when I brush/vacuum the pool it just seems to stir things up more and make it more cloudy. But I'm not really seeing any residue. I am thinking about adding some DE to my sand filter. We are due for more heavy rain tomorrow so that may skew my numbers tomorrow night and Saturday.

I'm just not sure if I am really dealing with an Algae problem or something else. So any advice would be really appreciated!

 

[needsajet]

It sounds like you are dealing with algae. When it dies, it should get cloudy white or cloudy blue from being able to see the dead algae "carcasses". It will take some time to filter that out. There's no point doing the OCLT until the pool is clear. When it is, you will very likely get the low drop of 1 ppm FC or less.

As long as you do the test both times yourself with your same level of care, you will get better accuracy from test to test. If several different people do the testing, the test is less accurate.

Until you're ready to do the OCLT, you can use a 5 ml sample and count each drop as 1 ppm, if you like.

Stirring up the dust is a good thing because it helps the organic material to find its way to the filter.

 

[domct203]

..............
Since my SLAM level is 31, that means that to measure I am putting in 62 drops. 10% of 31 is 3.1, but when I do an OCLT I can't have lost more than 2ppm. This morning i had lost 2.5, which is obviously more than 2, but still within the 10% variance given the high FC. Hopefully I'm making sense! I'm just not sure whether 2.5 is acceptable or not.

Were you certain to shut off the SWG during the OCLT?

To pass an OCLT, the FC loss must be 1ppm or less, NOT 2ppm, & anything over 1ppm is a fail.

How To Perform The OCLT

I have found in my experience, if you are very meticulous with your testing, the error rate in the test itself is very low. I've done multiple tests in a row from the same collected sample and will be within 1 drop up to 20ppm (40 drops).

The 'trick' is to have the same size sample for every test (I use the Taylor Sample Sizer), mix thoroughly (I use a Taylor Speed Stir), and hold the R-870 bottle as vertically straight as possible when dropping. Let the drop form naturally, and drop off naturally. I never drop faster than 1 drop per second.

 

[rdy2fly]

Thank you both for the replies. I was wondering about only doing a 5ml test!

And yes, SWG was off doing the OCLT




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