Calcium levels in Plaster SWCG pool

[Dirk]

I'm not 100% sure about my CH testing. When it actually turns full-on blue is still a bit of a mystery to me. I know I'm under 400. I know I'm over 300. But I'm not quite sure if it's 325 or 350. Somewhere in there. My fill water is CH-zero, so I'm not expecting any rise. I actually lowered it a bit this winter fooling around with rain water. So I'm thinking I need to up it a bit to at least 350. Just to play it safe with my relatively new pebble.

Does anything contribute to CH besides fill water? What I don't want is for my pebble's plaster to be contributing to my water's CH! That's bad, right?

 

[tomfrh]

I’ve wondered the same thing about the colour. I turns blue, but another drops makes it more blue. Which one counts as “turns blue”?

 

[Dirk]

I’ve wondered the same thing about the colour. I turns blue, but another drops makes it more blue. Which one counts as “turns blue”?

There are some notes here, about a fading endpoint, that might help. I haven't tried this yet:

Pool School - Calcium Hardness


I get the purple. I keep going until it turns blue, and no more drops make it any more blue. I subtract the last drop. I'm struggling with two things. I think I've noticed that the blue color deepens just with time, like the longer it sits there the bluer it gets. And because I'm trying to juggle how much time to leave between drops, and the very subtle difference in shades of blue towards the end, and because I'm old and feeble, I sort of lose track of when the last drop was actually the last drop!

That's why I'm sure of the 300 and 400. It turns very blue long before 400 (like around 350-360) and it's no where near blue enough at 300. So I know I'm between those two numbers! But I get a bit lost around 320-330-ish and end up guestimating... That's why I'm thinking I should add a bit of calcium. Because if I could test and be sure it's more than 350, and less than 400, then at least my plaster is safe while I continue to fine tune my skills for this particular test. TA is a similar if somewhat less of a challenge. FC and pH and salt are cake compared to CH. CYA is in a league of it's own.

 

[tomfrh]

Thanks. That’s clarifies it for me.

Your problem is a level of sophistication beyond where I’m at!

 

[Dirk]

Ah... the level of my problems...

 

[tomfrh]

I’ve raised the CH to ~375 now.

The water doesn’t look quite as clear
anymore. When does CH begin to affect clarity?

 

[Dirk]

I’ve raised the CH to ~375 now.

The water doesn’t look quite as clear
anymore. When does CH begin to affect clarity?

A bit above my pay grade. But I haven't read here yet anything about clarity and CH. You mentioned you were in the middle of a slam. Have you completed that? Or do you think you have? Water clarity is one of the three tests for determining the end of a slam. If your water isn't clear, you're not done with your slam. Have a look:

Pool School - SLAM - Shock Level And Maintain

 

[tomfrh]

The SLAM was complete. Clear water, negligible overnight chlorine loss, no detectable combined chlorine.

I've recently added acid (to reduce my TA), and also added the Calcium CHloride to raise the CH from ~200 to current value of ~375.

I've had issue with Calcium causing cloudy water previously (when I used economy chlorine), so I wondered if that was it...

 

[cfherrman]

People have their ch in the 1000 sometimes and have clear water er, should clear up

 

[tomfrh]

People have their ch in the 1000 sometimes and have clear water er, should clear up

ok thanks. good to know.

 

[tomfrh]

The cloudiness went away after a few days. CH is now 375-400

 

[Dirk]

Ta da!

Good work! Happy with your CSI?

 

[tomfrh]

CSI saying ~ -0.3

 

[Dirk]

CSI saying ~0.3

So the consensus here is -0.6 to +0.6 is in range. -0.3 to +0.3 is preferred. So you're good!

But it's also consensus here that a "slightly negative" CSI may help to keep the calcium build up off the plates of your SWG. I'm working through this myself in another thread with some TFP experts, and I'm trying to get to the bottom of what "slightly negative" means. I've just recently read as low as -0.3. So I've determine a target of -0.2 is right for my pool, because I figure the natural swing of all my levels will have my CSI wandering around -0.1 to -0.3.

If you have to regularly clean calcium off your SWG, this might be something for you to think about... There are those here that don't have to clean their SWGs, by using this principle...