Proof that CYA matters and what UV does to free chlorine

[MrXYZ123]

I thought this was pretty cool. It shows how the chlorine in our 40k gal pool is destroyed by UV during the day and then how I verify that there is nothing consuming the chlorine overnight with what's effectively an overnight free chlorine loss test.

The points on the graph from Sutro tests equate to 1am, 6am, and 7:30pm. So basically overnight, dawn, and dusk.

My liquid feeder broke this week and I have been manually dosing with liquid at 8pm every night (sux).

My CYA is 40ppm and the pool is in direct sunlight for a minimum of 8 hours/day.

 

[Texas Splash]

Yes, a well-balanced CYA is exceptionally important. My pool would never survive with a CYA of 40. Even before I went to salt, my CYA was 60-70 this time of year through Sept. Crazy hot and intense UVs.

 

[MrXYZ123]

Yes, a well-balanced CYA is exceptionally important. My pool would never survive with a CYA of 40. Even before I went to salt, my CYA was 60-70 this time of year through Sept. Crazy hot and intense UVs.

Ya I am going to 60 as soon as I can get my hands on some CYA.

 

[Mdragger88]

If those fc numbers are accurate you’re dipping too low for your cya.
That’s an open invitation for algae & other nasties. Dose higher so you don’t risk falling below minimum before the next dose.
FC/CYA Levels

 

[MrXYZ123]

Thanks. I am using BlueRayXL so it reduces the chlorine demand and that keeps the algae under control and water is good. We don't use the pool much so there isn't really a lot of chlorine demand and the water stays clear. I'll definitely agree that 1.6 is opening the door, but it is inky there a couple of hours per day. I will fir sure bump up FC when I get to 60ppm on CYA.
* I know minerals aren't part of the TFP philosophy, but it helps when I travel and am not able to keep chlorine in the range I need (another reason I wish I had a SWCG). Small investment to save $ on chlorine and also have a little insurance when chlorine gets out of range.

 

[Newdude]

I know minerals aren't part of the TFP philosophy,

You cannot test the water to know that it's sterile with minerals. So yeah. No.

the water stays clear

Algae, while unsightly, is harmless. The dangerous things aren't ever visible.

 

[Mdragger88]

With a liquid feeder it should be pretty simple to adequately chlorinate the pool while away. (I realize you said it’s broken right now)
Regardless of supplemental minierals/metals the proper fc/cya ratio should be maintained at all times to ensure proper sanitation.
As @Newdude mentioned you cannot see pathogens
Clear doesn’t automatically = sanitary or else you’d only get boil water alerts if the tap water looked bad.

 

[markmarkanthony122]

Awesome observation. I got a Sutro this season, and it definitely helps me keep an eye on chlorine and pH in between my full tests. I travel each week for work and can’t test manually, so it’s an extra set of hands. I wish it had another cartridge that would test CYA, CH, and salt, though. I'd be set for life!
Well, I guess if it would brush and add chemicals then I'd be set lol.
"Let's get a pool the family said, it will be worth it and we will help"

 

[cledee]

We only get 2 1/2 - 3 hours of direct sunlight on the pool, we are shaded by trees so I am able to start out with 30ppm CYA in May, I bump it to 40ppm for June, July, August and able to let it fall back down into 30ppm for September. It's been a cloudy wet summer so we've had a couple of weeks of me only having to add 1 to 1 1/2 gallons of chlorine for the week.