Pink slime!

[famousdavis]

Thanks chem geek.

Taken what you and waterbear have written, I can conclude that the pH stability was borne from stopping my waterfall and by tamping down the ontime for my SWCG -- two causes for pH rise. This morning I opened the valve to the spa just a little so the water is replaced with filtered/chlorinated water, but it's just a water drip now, not a waterfall. ;-)

Forgot to mention that I used to measure muriatic acid until I read (somewhere here, maybe?) that adding the measuring step may cause more harm than good because it's an extra step that might lead to an accidental spillage of acid. So, I've just guesstimated my acid additions (with fairly consistent results - my pH would fall back to 7.2). I'll try guesstimating a smaller dose of acid from now on. Measuring acid is actually fairly easy by just looking at the acid container's liquid level, and calculating what a few cups poured out would look like. The thing I haven't done is perform an actual acid demand test to calculate with more precision just how much acid I should add. I'll do that the next time my pH needs downward adjusting, just so I can better estimate my acid demand needs.

Fine work, gentlemen!

[waterbear]

Thanks chem geek.

Taken what you and waterbear have written, I can conclude that the pH stability was borne from stopping my waterfall and by tamping down the ontime for my SWCG -- two causes for pH rise.

And the second reason is why the CYA should be at the maximim since it will mean that a lower on percentage will maintain the desired FC level. Lower on time means less aeration means slower pH rise.