Started seeing algae spots despite balanced water

[NjPool84]

Hi,
Pool owner of several years, never really had an algae problem. This past week I've started seeing small algae spots pop up over night. I brush them off, run the filter. Even on areas of the liner that don't have visible spots I see some stuff (likely algae) coming off in a cloud.

My levels as of 5 minutes ago:
FC: 4.5
CYA: 45
PH: 7.6

Earlier in the week I hosed down my filter element (quad cartridge) and everything inside. This is part of my twice-a-summer maintanance. The cartridges weren't too bad.
I've vacc'd the pool once this week (going to drop the bot in this morning).
I have friends coming over later and I assume there isn't an issue with swimming.

I consider myself a relative expert when it comes to maintenance, pool knowledge, chemistry balance etc. Friends and family come to me for advice. I've sent them here to this page as well as recommended the taylor test kit. However, considering the chem levels noted above, pool is not green and is clear, considering how I am meticulous with the pool and check it every day as part of my morning routine... Kind of baffled how Im seeing algae spots. I thought it was high CYA without the proper high level of FC, but thats not the case (4.5/45 noted above). I thought it was my filters clogged of gunk, organics, algae but thats not the case (they werent bad and I hosed them down last Saturday).

I understand the recommended regime to get algae out is SLAM and process it out. But if the levels are fine to begin with, why is it happening in the first place?
Any thoughts?

 

[cledee]

Hi,
Pool owner of several years, never really had an algae problem. This past week I've started seeing small algae spots pop up over night. I brush them off, run the filter. Even on areas of the liner that don't have visible spots I see some stuff (likely algae) coming off in a cloud.

My levels as of 5 minutes ago:
FC: 4.5
CYA: 45
PH: 7.6

Earlier in the week I hosed down my filter element (quad cartridge) and everything inside. This is part of my twice-a-summer maintanance. The cartridges weren't too bad.
I've vacc'd the pool once this week (going to drop the bot in this morning).
I have friends coming over later and I assume there isn't an issue with swimming.

I consider myself a relative expert when it comes to maintenance, pool knowledge, chemistry balance etc. Friends and family come to me for advice. I've sent them here to this page as well as recommended the taylor test kit. However, considering the chem levels noted above, pool is not green and is clear, considering how I am meticulous with the pool and check it every day as part of my morning routine... Kind of baffled how Im seeing algae spots. I thought it was high CYA without the proper high level of FC, but thats not the case (4.5/45 noted above). I thought it was my filters clogged of gunk, organics, algae but thats not the case (they werent bad and I hosed them down last Saturday).

I understand the recommended regime to get algae out is SLAM and process it out. But if the levels are fine to begin with, why is it happening in the first place?
Any thoughts?

CYA of 45 is really 50, at 4.5 FC you are close to the minimum FC. You should be targeting 6-8 FC. It's possible overnight if your pool is at the minimum that certain spots on your pool are falling below the minimum allowing algae growth.

 

[JJ_Tex]

Unfortunately your 4.5 FC is flirting with the minimums and is below the recommended range.

For your CYA of 50 (45 rounded up) the target range is FC of 6 to 8, and bare minimum of 4. Here is a chart I put together to help me visualize the various targets of FC based on the CYA.

 

[NjPool84]

Yeah, I thought about that too. Maybe the FC drops low enough towards the beginning of the evening before the filter (and chlorinator) have a chance to pump up the FC allowing some algae growth. I'll bump it up and drain pool next week slightly (2-3 inches and refill) to see if that'll balance it all out nicer.

 

[JJ_Tex]

It could be a number of things... maybe that area gets less circulation and therefore has a slightly lower FC, maybe a bird pooped in the pool, maybe you had a higher bather load and dipped below minimum for a while.

Regardless, sounds like you have a solid plan. As you can see by my avatar, I like to run my FC "hot" to keep far away from the minimums and give myself plenty of buffer for those type of events mentioned above.

 

[SoDel]

Hi,
Pool owner of several years, never really had an algae problem. This past week I've started seeing small algae spots pop up over night. I brush them off, run the filter. Even on areas of the liner that don't have visible spots I see some stuff (likely algae) coming off in a cloud.

My levels as of 5 minutes ago:
FC: 4.5
CYA: 45
PH: 7.6

Earlier in the week I hosed down my filter element (quad cartridge) and everything inside. This is part of my twice-a-summer maintanance. The cartridges weren't too bad.
I've vacc'd the pool once this week (going to drop the bot in this morning).
I have friends coming over later and I assume there isn't an issue with swimming.

I consider myself a relative expert when it comes to maintenance, pool knowledge, chemistry balance etc. Friends and family come to me for advice. I've sent them here to this page as well as recommended the taylor test kit. However, considering the chem levels noted above, pool is not green and is clear, considering how I am meticulous with the pool and check it every day as part of my morning routine... Kind of baffled how Im seeing algae spots. I thought it was high CYA without the proper high level of FC, but thats not the case (4.5/45 noted above). I thought it was my filters clogged of gunk, organics, algae but thats not the case (they werent bad and I hosed them down last Saturday).

I understand the recommended regime to get algae out is SLAM and process it out. But if the levels are fine to begin with, why is it happening in the first place?
Any thoughts?

I agree with the “every pool is different” so idiosyncrasies of your circulation, sun exposure vs test time, mass bird poop event, aliens peeing in it at night, who knows, etc., may mean you need to maintain more chlorine than close to the bare minimum for your particular pool. The small algae spots are your indicator. It will do no harm to stay on the high side of the recommended range and may save you from a lot more work if the spots were to turn into a full bloom somewhere in the season.

Out of curiosity, how did you get 45 as the CYA result? I still have trouble with repeatable results of that test within +-10 or so. Running so close to the minimum based on the inherently subjective CYA test may also explain part of the issue?

 

[jgofnj]

I find brushing to hit those "dead spots" really helps. Do you brush a few times a week?