Hello all. So I’ve had my pool a few years now, and have had a good test kit, and pools always been spotless. It’s a 21’ above ground, chlorinated with bleach, with a heater. For some reason this summer I’ve been having a hard time keeping the cya up, and have already added stabilizer once. I’m good about maintaining chlorine levels though. All of a sudden in the last day the pool is cloudy with what looks to be algae on the bottom, kids were just swimming yesterday and they said it was just a little cloudy. FC was 2.6 this morning before adding anything, CC was .1. PH 7.5, cya is below 20. I haven’t had to shock the pool in a long time, just curious what you think would cause such a rapid decline? Thanks, Ryan
Sudden algae bloom?
- Thread starter Krally
- Start date
- Jun 22, 2014
- 48,090
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
We can't see any of your water test results, but based on what you noted above about an FC of 2.6, that's quite low for summer in warm water. That combined with a heavy bather load is a combination for algae. Sounds like it's time to do a SLAM Process.
Ok. Kind of what I was thinking. Think I shoot for around FC of 4, I’ve been trying to keep it around 3, but it definitely drops pretty quick between the amount of use and the amount of direct sunlight it gets. Pool is about 84 degrees and it’s been hot. Thanks
- Feb 6, 2015
- 6,279
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
CYA "below 20" is allowing the FC to burn off quickly. Add any bather load to that and you are a prime candidacte for algae.
Do an Overnight Chlorine Loss Test.
If you fail the OCLT, you will need to do a proper SLAM Process.
Fill out your signature with pool, pool equipment (including manufacturers and model numbers) and test kit info.
This assists us in providing help specific to your pool without needing to ask you each time.
Do an Overnight Chlorine Loss Test.
If you fail the OCLT, you will need to do a proper SLAM Process.
Fill out your signature with pool, pool equipment (including manufacturers and model numbers) and test kit info.
This assists us in providing help specific to your pool without needing to ask you each time.
- Jun 22, 2014
- 48,090
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
The ideal FC level (or elevated SLAM FC level) all depends on your current CYA. Have you confirmed your CYA yet? If so, then you go to our FC/CYA Levels to find the proper FC level.
- Jun 22, 2014
- 48,090
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Oops, disregard. You posted your test results while I was asking that last question. 
Ok. We have to add water pretty frequently between the kids splashing and sun exposure, thinks that could be what’s causing a hard time keeping CYA up?
- Jun 22, 2014
- 48,090
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
I agree with Gene's comment above. An Overnight Chlorine Loss Test is in order. You might also consider adding 20 ppm of stabilizer to get the CYA to 30. Spalshout can result in the loss of some CYA. The kids would have to be doing a lot of cannonballs to loose a lot of CYA.
My Taylor CYA test tube only goes as low as 30, so honestly I’m estimating around 20-25?
- Jun 22, 2014
- 48,090
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Yes, so when your CYA is deemed to be below 30, it's best to add 10-20 ppm worth of stabilizer. In the summer you need it anyways. If you fail the OCLT, then your FC SLAM level will either be 12 or 16 depending on if your CYA ends-up being 30 or 40. All of this per the FC/CYA Levels.