Doing a SLAM when CYA and CC are both zero

nadar

Active member
Oct 21, 2018
33
Northern Tennessee
We opened up our mesh-covered pool yesterday. The water is so green that you can't see the bottom. I have a feeling that there is a lot of leaf debris on the bottom since our pool is surrounded by trees but I was afraid to vacuum since I couldn't see what I was doing. I was getting ready to start a SLAM but could use some advice before I start. Here are our test results, taken 3 hours after opening:
FC - 1
CC - 0 (how is this possible since the water is green?)
PH - 7.8
TA - 80
CH - 100
CYA - appears to be 0
I was surprised that CC and CYA were both at 0 so I took a sample to a local pool store that uses a Clear Care Expert Water Analysis System to get a second opinion. They also said that CC was 0, but they claim that the CYA is 22. Reagents haven't expired but I find the CYA test hard to interpret. It was 60 at closing so I have a hard time believing that it is 0 now. Should I proceed using the shock level for 30 (which is 12) and add some CYA in a sock in the skimmer beforehand to get CYA to 30? Or should I proceed using the shock level for 20 (which is 10) and add a tiny bit of CYA to a sock in the skimmer to get it to 30, and then increase the dose to 12 afterwards? Since I wasn't able to find enough liquid chlorine to do the entire SLAM, could I start off the SLAM with Dichlor so it will increase CYA and decrease PH at the same time so I wouldn't have to add muriatic acid and granular stabilizer to the pool? And when I run out of liquid chlorine, should I switch over to Cal-Hypo, and can I broadcast it instead of adding it to a heavy bucket of water and pouring it around the pool?
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
13,317
Evans, Georgia
CYA does degrade slowly. How a pool store arrived at "22" is a mystery since the test is logarithmic and not linear. Your pool be green from leaves or metals or other reasons. You might have a skosh of CYA that is too low to show on the tests as either 20 or 30 (i forgret?) is the lowest the vial reads.

Before you start a SLAM process, I'd use a leaf rake and scoop out absolutely as much as you can. Every bit of chlorine you put in that water will be working to oxidize the solids and do little for the green until the solids are gone.

Then you should raise your CYA to 30ppm, and lower your pH to 7.2 and proceed with the SLAM process,


Maddie :flower:
 
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