Should I add CYA?

[salinda]

Numbers today:
ph 7.2
FC 5
CC <0.5
TA 70 (yay!)
CH 750
CYA 40
Salt 5200
Borate 0

Temp 82-86

I have a SWG and have always tried to run the CYA at 70. However, this year I did a big SLAM cycle due to tenacious waterline algae and also algae in the pool cleaner hose. Since that SLAM (more than a month ago), my SWG has had NO problems maintaining FC at 5, even with warm water and sunny days. I have had to run it at 100% in the past but I don't have to do so any longer. My CYA was almost 0 before the SLAM, so I SLAMmed the pool and then did 50% of the increase I needed to do and am now at 40. I still have 8 lbs of CYA.

Since the pool is maintaining FC well, should I still increase the CYA? Maybe I can run the FC at a lower level? Maybe the few dots of algae starting to show near the water line are telling me to continue the CYA increase?

 

[ping]

You should not be seeing algae if the SLAM was completed per our recommendations and you have maintained the FC at the proper levels. I was going to say to raise the CYA to 70/80 range until I read the last sentence of the post. You need to determine why the algae is coming back before you raise the CYA.

Before adding more CYA I recommend you take care of any algae as it will only take more chlorine to get rid of it once the CYA level is raised.

 

[RobbieH]

A few dots of algae around the water line means your FC is dropping below the minimum range, especially around the surface. I found that I needed to target FC around 6-7 instead of 3-5 so that FC would stay strong enough around the tile line. Regarding that algae at the tile line, is it black algae? Black algae takes a good hard scraping to remove, such as a fingernail or wire brush. If this is what you have, just raising FC won't help, you will have to brush it good and hard too.

Raising CYA will help to keep FC from dropping, again this can help you at the water line, where you seem to be having problems.

 

[timerguy]

Problem is, you needed to add the cya while you were slamming in the first place, then adding it again when you finished the slam to get it to 70-80. It's too late now, obviously you have some algae in your pool now that may require slamming again. You don't want your cya any higher to do the slam.

 

[salinda]

Timerguy: I only added CYA the first time after the pool passed the overnight test. The pool is at 40 now.

RobbieH-I think you're right. I've been away and not brushing. The algae has taken hold over years but is still extremely minimal. I can honestly live with it. I'm wondering if increasing CYA will hold the FC better at water line on hot days? Should I shock again first? Just raise CYA and brush and see what happens?

 

[salinda]

Update: I added CYA right after this last post below, so maybe on 8/5. I haven't remeasured yet (waiting for some acid to mix in to measure everything) BUT ALL OF THE ALGAE AT THE WATERLINE HAS DISAPPEARED!!!! It was just a few spots in grout on the shady side of the pool. My pool is older so I don't have enough circulation at the surface so this is probably a slightly more stagnant.

Proper CYA levels for SWG, which seem high to non-SWG users, seems to keep the FC more stable at the surface based upon this observation.