Any connection between SWG and calcium deposits?

[chem geek]

Evan's (waterbear's) advice is excellent and will address the pH rise you are seeing and the amount of acid you have been adding. The part that doesn't make much sense to me are the calcium deposits on the spa spillway tile. With the numbers you posted I did two things (in my infamous spreadsheet) to see if I could figure out when scaling might occur. I first used a high spa temperature of 104F since higher temperatures lead to more scaling. Then I saw what sort of pH would be needed to get scale and though "balanced" water would have a pH of around 7.3, scaling normally wouldn't occur until you got to nearly 7.8. And yes, the indices that calculate this stuff are controversial so enough said about that.

So I have two thoughts about this. First, is when you startup in the spring, if you are willing to experiment then before you lower your TA and add Borax see when your pool/spa is adding deposits again. Then, test your spa water when this occurs. Perhaps the aeration and high temps of the spa have raised its pH quite high. If that is true, then the things that waterbear suggested should help reduce the scaling problem. Of course, even if you test and things look normal, waterbear's advice is still good to slow down the pH rise and reduce your use of acid and should be tried anyway to see if it eliminates this scaling problem.

My other thought is that perhaps this isn't scale but is something else. At first I thought it might just be evaporated salt, but this is a spillway and not splash-out on coping. Anyway, those are the random thoughts I had...at least you've got a good plan from waterbear that is sure to address some and probably all of the issues you are having.

Richard

[SoCalBoo]

Evan's (waterbear's) advice is excellent and will address the pH rise you are seeing and the amount of acid you have been adding. The part that doesn't make much sense to me are the calcium deposits on the spa spillway tile. With the numbers you posted I did two things (in my infamous spreadsheet) to see if I could figure out when scaling might occur. I first used a high spa temperature of 104F since higher temperatures lead to more scaling. Then I saw what sort of pH would be needed to get scale and though "balanced" water would have a pH of around 7.3, scaling normally wouldn't occur until you got to nearly 7.8. And yes, the indices that calculate this stuff are controversial so enough said about that.

HMMMM. Interesting. I will tell you that I haven't used the spa much at all recently. In fact, if it gets used more than one a week during summer, and one a month during winter, it is a rarity.

So I have two thoughts about this. First, is when you startup in the spring, if you are willing to experiment then before you lower your TA and add Borax see when your pool/spa is adding deposits again. Then, test your spa water when this occurs. Perhaps the aeration and high temps of the spa have raised its pH quite high. If that is true, then the things that waterbear suggested should help reduce the scaling problem. Of course, even if you test and things look normal, waterbear's advice is still good to slow down the pH rise and reduce your use of acid and should be tried anyway to see if it eliminates this scaling problem.

See above. doubt we've got a temperature issue worth mentioning. right now, spa and pool are a crisp 52F. However, it is true during summer that both pool and spa are in high 80s around clock.

My other thought is that perhaps this isn't scale but is something else. At first I thought it might just be evaporated salt, but this is a spillway and not splash-out on coping. Anyway, those are the random thoughts I had...at least you've got a good plan from waterbear that is sure to address some and probably all of the issues you are having.

Pretty darn certain it is scale. evaporated salt would come off tile much easier, and would likely do so with just scrubing and pool water. this stuff takes a fair amount of diluted acid (don't worry, I'm careful...did a lot of chem labs in college, so I know what the stuff can do if you are not careful). the scaling also occurs in a few other areas, notably a few nooks and crannies just above the water line where circulation isn't great. with my calcium getting higher...I just assumed it was scaling.

Richard

Thanks all