My numbers seem ok but I still get algae in some spots on the walls every 10 days

[citznfish]

Mostly where the sun hits the pool walls the most. Is this normal? The pool store employee said I shouldn't get any if my water is balanced.

My alkalinity is just on the edge of being high but I can't imagine this is the cause. CYA is in range but on the low side.

FC is 5.5 (I boosted the chlorine a touch to see if it would help)
Drop is 6.0

SoCal pool, pebbletec, saltwater.

 

[JJ_Tex]

For once I’ll agree with a pool store employee, algae is not normal in a balanced pool.
And by balanced I mean your FC level for your CYA. Chlorine is the only thing that kills algae.

For your CYA, 5 is the target and you never ever ever want it to get close to 3 which is your minimum. Since you see algae spots, your chlorine is low. Is the 5.5 after you upped the chlorine?

The correct answer is to SLAM when you see algae. You could run hotter for a week or so and see if that does the trick if the algae is just getting started, but don’t be shy about SLAMing if upping the chlorine a bit doesn’t work.

My CYA is 70 as well and you can see my FC in my avatar is much higher than 5. I’ve never had a speck of algae and most people who swim in my pool tell me how much they love that my pool doesn’t have a lot of chlorine.

 

[Mdragger88]

Your fc must have fallen below minimum for your cya of 70 (65 counts as 70) at some point.
Visible algae = SLAM Process time
Can you share your logs?
How long & what % are you running your swcg?

 

[Newdude]

You're exactly the reason why we added a 'range' to the SWG reccomendations last winter. Targeting a hard 5 is a fools errand for most people these days with oversized units and/or night time production to save on electric bills. Even my pool with 24/7 operation has some swing as I make my days FC across 24 hours but lose 100% of that days loss in 6 to 8 hours.

Anywho, up your target considerably. Like double. We round up your 65 to 70, and if you lose unexpected FC at 10, you're still sitting pretty. When the same happens at 5 FC, you don't have much wiggle room and algae starts popping up.

 

[citznfish]

For once I’ll agree with a pool store employee, algae is not normal in a balanced pool.
And by balanced I mean your FC level for your CYA. Chlorine is the only thing that kills algae.

For your CYA, 5 is the target and you never ever ever want it to get close to 3 which is your minimum. Since you see algae spots, your chlorine is low. Is the 5.5 after you upped the chlorine?

The correct answer is to SLAM when you see algae. You could run hotter for a week or so and see if that does the trick if the algae is just getting started, but don’t be shy about SLAMing if upping the chlorine a bit doesn’t work.

My CYA is 70 as well and you can see my FC in my avatar is much higher than 5. I’ve never had a speck of algae and most people who swim in my pool tell me how much they love that my pool doesn’t have a lot of chlorine.

I promise you my FC is between 5 and 5.5. I haven't added any, the chlorine generator takes care of it.

This is why I am confused about the algae appearing.

I did notice a miniscule amount in the threads for the top of my leaf catcher and a few spots on the pool cleaner vacuum. I'm going to scrub it all tomorrow.

 

[SoCalPoolFool]

+1 Shoot for 10 FC with that CYA level. Brush and vacuum every week. Keep filters clean and run the pump 24/7 if it's variable speed. Don't fight your pool enjoy it. An ounce of prevention is worth a gallon of cure.

 

[JJ_Tex]

I promise you my FC is between 5 and 5.5. I haven't added any, the chlorine generator takes care of it.

This is why I am confused about the algae appearing.

Yeah, on paper you shouldn't have algae, but sometimes paper cannot always explain real life. Maybe it dips down below the mins sometime when the pump is not running, maybe a bird pooped in the pool, maybe that area gets less circulation, maybe you had a power outage you didn't know about, maybe one day you had a heavier bather load that dropped you below the minimums, etc.

Don't beat yourself up, just know that your pool is telling you it needs a bit more more chlorine. You have a SWCG so that's easy to do. You can also add liquid chlorine for an immediate boost.

 

[citznfish]

Update: I went on vacation so I didn't do a SLAM. I brushed down all the minor algae and ran a super chlorinate the night before I left

I did test my CYA at 80 and FC at 9 the next morning before I left.

came back 10 days later to a still algae free pool. Seems I need to keep a higher FC than previously thought. Although 4-5 FC worked well for the last 7 years.

tested FC today and it's now at 12ppm. Too high so I'll bump the chlorinator down to 70% of the time the pump is on high (4 hours)

so it seems things have settled down now, that's a relief.

 

[proavia]

With a CYA of 80, minimum FC is 4 and target is 6-11.

Treat minimum as the FC number you NEVER want to get below at any point . You need to account for FC loss during the day amd with high swimmer load. Always shoot for the high end of the target range.

Be aware that pH test will read falsely high with FC > 10.
What hours does your pump run?
What time of day do you test FC?