Rebalancing after conversion to SWG

[rosensama]

Hi All,

I've just converted converted the pool at my new home to salt. I've been shifting the chemistry to an SWG setup and the pool has just started fading from crystal clear to picking up a slight green tint and getting cloudy. I'm shocking it right now, but can't understand why this is happening given the pool chemistry. I've been measuring every day as part of the rebalance and the numbers are coming up consistent, so I don't think it's measurement error.

FC: 4 - 6 depending on cloud cover
CC: 0, not the slightest hint of pink any time I've tested this
pH: 7.2 - 7.8, so far dialing this in has been the hardest part
TA: 70
CH: 450, the water's hard here, not much I can do to get it lower, didn't present problems when I was using bleach
CYA: 70-75
Salt: 2700
Water Temp: ~85

No complaints on the Nano display, so how's it managing to green up on me?

Thanks,
Rob

 

[needsajet]

Nice to meet you via TFP

There's no real way to know the exact reason for visible algae and cloudiness, but the key right now is to SLAM the pool.

This is the TFP procedure for the SLAM: Pool School - SLAM - Shock Level And Maintain

The procedure needs to be followed thoroughly, and after that, you'll have better luck getting the water stabilized.

Are you using muriatic acid for your pH adjustments?

 

[jeffchap]

Algae is always the result of insufficient chlorine. Given enough chlorine, algae simply cannot survive.

We always round up our CYA to the next 10, so if you are 70+, read that as 80. The bare minimum FC for that is 5.6. If you've dropped to 4, that's too low. SLAM to kill it then target FC at 8 and never let it fall below 6.

 

[needsajet]

It appears that the OP was following TFPC recommended FC levels for their SWG pool and CYA at 80 ppm. The bare minimum is 4 ppm FC and the target is 6 ppm FC.

A few things that may contribute to an algae outbreak include lack of brushing, dead spots with inadequate water circulation, or higher than normal incoming load of organic contamination. It's indeed very important that the pool never fall below the bare minimum FC level.

 

[rosensama]

Algae is always the result of insufficient chlorine. Given enough chlorine, algae simply cannot survive.

We always round up our CYA to the next 10, so if you are 70+, read that as 80. The bare minimum FC for that is 5.6. If you've dropped to 4, that's too low. SLAM to kill it then target FC at 8 and never let it fall below 6.

I hear ya, but for what it's worth, the pool calculator says for SWG to target an FC level of 3 at 70 and 4 at 80. I understood those values to be the floor and haven't let it dip through them. Are you sure about your numbers? If the calculator is wrong and the floor is 6, then maybe that's what's going on. I'm guessing this is the point where I should keep in mind that the pool calculator is a set of suggestions and I need to adjust based on what I observe.

I am SLAM'ing. I guess you are all over me because I said I was "shocking" the pool, but that's what I meant.

Tangent . . . with FC < 5 so rarely a goal, too bad the easy tests stop there.

- - - Updated - - -

Nice to meet you via TFP

There's no real way to know the exact reason for visible algae and cloudiness, but the key right now is to SLAM the pool.

This is the TFP procedure for the SLAM: Pool School - SLAM - Shock Level And Maintain

The procedure needs to be followed thoroughly, and after that, you'll have better luck getting the water stabilized.

Are you using muriatic acid for your pH adjustments?

Yes, I use muriatic acid when I need to lower pH.

 

[needsajet]

You're interpreting the recommended levels correctly. Some do use higher numbers quite successfully as well.

There's no harm in the word "shocking" because it's a key part of doing a SLAM. Dropping pH to 7.2 before starting a SLAM, brushing regularly, and observing the endpoint criteria are just as important.

 

[jeffchap]

Sorry, I forgot there is a separate CYA/FC chart for SWGs. I just always keep it my head: 7% of CYA as a minimum, 10% + 1 as a target, and 40% for a SLAM. I use those values even with my SWG, preferring to err on the high side.