FC not reaching SLAM level

[jmcmanlove]

Might be too soon to ask for help but this is my first time SLAM’ing our pool.

We have a 10K pool. At the start of the SLAM our FC was 0 and CYA was 30 so I added 205 oz of 10% liquid Cl to achieve an FC of 16 ppm. I did all of this after sunset.

I waited about 45 minutes to retest just to see where the FC level was. I got a measly 4.5 ppm…nowhere near 16. We have no visible algae and no CCs, but we lose about 2-3 ppm of Cl overnight, which is why we’re doing the SLAM.

Is this normal? Or am I messing up the testing somehow? Anything else that could be going on? Also, pH was at 8 to start but I added enough acid to get it to 7.3 about 30 minutes prior to beginning the SLAM.

Any advice is greatly appreciated!

 

[Texas Splash]

Is this normal?

Certainly could be with excessive organics. Ignore the pH for now when you are doing the SLAM. It gets wonky with an FC over 10. FC gets used up quickly in the early SLAM, so do your best to stick with it. Are you using the 10ml sample size for your FC testing? Should be like this: 10 ml water sample + ONE generous scoop of powder. Count drops until clear and divide in half. Example: 20 drops to clear = FC of 10.

Also make sure your pool profile (size) is correct in the PoolMath APP and that you have the correct % bleach listed for the chlorine you are using. Hope that helps.

 

[jmcmanlove]

Certainly could be with excessive organics. Ignore the pH for now when you are doing the SLAM. It gets wonky with an FC over 10. FC gets used up quickly in the early SLAM, so do your best to stick with it. Are you using the 10ml sample size for your FC testing? Should be like this: 10 ml water sample + ONE generous scoop of powder. Count drops until clear and divide in half. Example: 20 drops to clear = FC of 10.

Also make sure your pool profile (size) is correct in the PoolMath APP and that you have the correct % bleach listed for the chlorine you are using. Hope that helps.

Thank you for the help! I tested before sunrise this morning and the FC and CC amounts were both at 1 ppm. Add more chlorine to get back towards that 16 ppm mark, tested a few hours later, and we were at 11 ppm. Still quite a bit of Cl loss but I'm in Phoenix were the sun is strong so I bet that loss is due to organics AND the sun.