Yellow spots

[mbeck5]

Good morning. For the last couple of months I have been seeing yellow spots on walls and floor of my pool, deep end and shallow. When I brush them, it looks like powder/cloud like and disperses. The spots can return after a day or sometimes several days or not for a couple of weeks. Sometimes there is one spot, sometimes several but I keep passing the OCLT. Latest results:

Last night This morning

FC - 6.5 FC - 5.5
CC - .5 CC - .5
Ph - 7.6
TA - 90
CH - 200
CYA - 55

The water is and has been crystal clear and feels great, but I am concerned. My CYA was at 30 for most of the summer and I added liquid conditioner this past weekend to bring it up to the current 55. Any suggestions? Should I consider this MA? Thanks for any responses. TFP has been a great process for the last few years and everyones support is much appreciated.

 

[mknauss]

Typically that indicates algae. Even though you pass the OCLT, you have visible algae so I would suggest a SLAM Process. Would have been a bit easier before you add the CYA but as the sun angle has dropped you should have less FC loss due to UV. If you are testing CYA of 55 be sure to use 60 as the gradation of the vial is not linear and thus we round up on CYA.

Take your FC to shock level and leave your pump running 24/7 at a low RPM. Brush each day. Check any hiding spots like light fixtures, ladders, skimmer weirs, etc. Should go quickly.

Take care.

 

[mbeck5]

mknauss, thanks for your guidance. Began the SLAM as soon as I read your post, brushed, added chlorine to 30 and reduced the RPM. The evening of the 5th I did an OCLT and the FC was 29, the morning of the 6th it was 27.5, kept it close to 30 for the 6th, brushed again and the OCLT started at 28 last evening and this morning was 27. CC has been .5 at every test. The water looks great as usual. I made sure to brush the return fittings, dont have any lights, ladders etc. Thanks again for your help. Hopefully almost 48 hours was enough!!

 

[mknauss]

Great to hear.

Take care.