Calcium deposits?

[chem geek]

Larry,

The deposits may be calcium carbonate because the combination of high CH, high TA, and high pH can lead to this scaling. Your typical readings through August had a saturation index of about 0.5 which isn't extraordinarily high (most people don't see cloudiness until 0.7 or 1.0), however your "this morning" numbers had a saturation index close to 1.0. I would have thought that the water would have become cloudy before you saw such deposits, but perhaps the evaporation of the water above the water line made the concentration much higher thus precipitating calcium carbonate.

As Sandy suggested, dilute acid will dissolve this scale. You should try and keep your pH down closer to 7.5 though you may have trouble doing this with your TA level at 130. If you find your pH rises frequently and you are always adding acid to lower it, then try lowering your TA level significantly down to 80 or below (using Ben's Lowering Your Alkalinity procedure) and see if this improves your rising pH and required acid addition. See this thread for more detailed info about possible sources of rising pH in SWCG pools.

Richard

[halefmly]

Sandy and Richard,

Thank you both for the replies. I will use your suggestions to get the scale removed, and also to get the TA reduced.

I have been reading the thread with Ben's method for reducing TA. I have a spillover from the spa into the pool, and also a fountain water feature in the spa. Will those alone create enough bubble action for the outgassing, or should I run the spa's air pump as well?

Larry

[chem geek]

Larry,

For fastest results, run the spa's air pump. The more aeration the better, unless you want to wait longer for the pH to rise (and TA to drop when you add acid). You should also make sure you get good mixing between your spa and pool water -- otherwise the pH rise, add acid, pH/TA drop process will happen much more in your spa instead of your pool.

Richard