Low Calcium Hardness with Scale

[RJPassan]

Greetings! We refinished our 20 year old pool in 2015 with SGM Diamondbrite. Over the first winter (closed and covered) it developed calcium scale. I know the solutions to get rid of the scale, so I'm not looking for that info. The scale was all over, but keeping the CSI low, it is now only on some of the walls. The scale doesn't look bad and doesn't seem to be harmful to the pool. Things like "no drain acid wash" will dissolve more than the scale, so I haven't done it.

SGM recommends Calcium Hardness of 200-400 with 200 being "ideal". My CH is now at 200. What I'd like to know is: if the pool water needs calcium, will it dissolve some scale BEFORE it attacks any of the regular finish? It seems that the scale on the walls is "calcium in reserve" ... is it harmful in any way (other than being rough)?

Thanks much for any good info!

 

[mknauss]

Not sure on the chemistry of attacking one kind of calcium over another. I would suspect whatever calcium is most readily 'dissolvable' (not sure that is a word!!) would go first.

Why would you get calcium buildup over the winter? Did your pH go sky high? Really high TA water?

Take care.

 

[RJPassan]

I'm hoping the scale is indeed the most 'dissolvable' calcium. If the calcium hardness level drops below 200 I will hate to add calcium with scale on the walls!

Opened 2016 with ph a little over 8 (closed in 2015 at 7.2) and TA of 50. Add acid and baking soda on a fairly regular basis to keep things in line. I've read other folks having scale issues with Diamondbrite although SGM will not admit any problems. I close in October and open in May ... no chem checks over the winter. Never had any problems with our plaster finish.