Strange SLAM behavior?

[pymalion]

Hi, all. It's starting to warm up a bit where I live, so I removed my pool cover this last weekend only to discover a green algae nightmare (by the way, last year was perfectly clear) . I think I closed too early last fall.

So, I began the SLAM procedure. First checked CYA - was at 0 after the winter closure. Used a sock to add some and am now at 30. Checked and adjusted TA and also made sure my pH was around 7.2. All good.

So, I got a bunch of bleach and brought the FC level up to 12-13ppm. After 30 minutes I rechecked and was back to 0, so I added more to return to 12ish. All going so far according to what I've read here.

But, here is where things get a little strange, I think. I checked again at the next 30 minute mark and the FC level was basically unchanged, around 11.5. So, I set about brushing all surfaces and then rechecked again at the 1 hour mark - barely lower, but the pool is still very, very green. To make a long story short, I have been checking my FC level (using FAS-DPD) every couple of hours and (easily) maintaining shock level, but the FC level is dropping super slowly, while tons of green remains. Overnight it only dropped by 3 ppm or so.

Is this normal? I had imagined from reading the sticky that the FC level would be dropping quite quickly while there was still a lot of green, and would only level off a bit once the green had turned to cloudy. Is this incorrect, or is there something strange going on in my situation? I'm not complaining, mind you - nice to not be burning through tons of bleach. But, I'm worried that something is not right, and the chlorine is not doing its job for some reason.

Thanks.

 

[JVTrain]

You may have had some of your CYA convert to ammonia, which will create a very high chlorine demand initially, until you oxidize all the ammonia. Then you're just battling the algae and organics. Likely you had a low level of ammonia remaining, explaining that first initial demand for chlorine. Now you need to let the chlorine work and keep that FC level at the shock level for your CYA until you get clear. It will take quite some time if your pool was green. Lots of brushing, lots of filtration needed to make progress on getting the green out.

 

[pymalion]

Thanks for the reply, JVTrain. I'm not surprised that it will take some time to get rid of the green - my surprise was really just that the amount of chlorine I am needing is so low. After reading the sticky, I had thought that I would probably have my FC level drop significantly each half hour until the green subsided, but that has not been the case. You seem to indicate that this is not that strange, though, even when the water is still very green, and that my initial high demand was likely due to ammonia from my CYA loss over the winter. If this is the case, then I am perfectly happy, and will just stick to the program for as long as I need to.

Anyone else have this experience?

 

[cowboycasey]

You may want to bring your FC to 16 and see if that helps.. How long did you wait to test for CYA after you added? usually takes about a week to see... what I am afraid is that you added up to 30 and maybe your CYA is at 40 or 50 now.

 

[pymalion]

Hi, cowboycasey. I think the CYA level is good - I used the amount calculated from PoolMath (and that I've used before), and have had consistent test results. Though, I did not wait a week to test - only a day or so, but the CYA was fully dissolved from the sock so I think it was well mixed.

I just read through the remainder of the sticky thread, and it seems to indicate that when the water is still cold, it can take longer to clear the algae (though using less bleach), as the oxidation slows down. I am thinking that is perhaps what is happening here, since my water is actually quite cold still (52 degrees F).

 

[kimkats]

I bet if you take a picture of your steps each day you will be able to see the color change. With just your eyes you will not notice but a picture........that is the way to go!

Kim

 

[JimbobT]

I bet if you take a picture of your steps each day you will be able to see the color change. With just your eyes you will not notice but a picture........that is the way to go!

Kim

+1 to that... The steps work great if it's really green.

When it starts to clear up a little bit; I start to use the drain cover in the bottom of the deep end.

 

[MarianParoo]

I believe that in cooler water the CYA may take longer to dissolve completely (even though the sock is empty), and disburse evenly.