Swimming Pool - EDTA? Ca++ levels?

[gibberdill]

A pool product (sequa-sol) was recommended -- sounds like it is an EDTA
solution. Supposedly it will prevent calcium scale from depositing on the
pool walls. I'm thinking of saving money buy putting my own EDTA solution
in from wholesale EDTA powder. What molarity are the commercial solutions?

Also, I've heard elsewhere that calcium chloride should be *ADDED* to
prevent metallic parts from corroding, or to someow maintain a balance of
dissoled solids. Doesn't this contradict the idea of sequestration of
calcium to prevent scale deposits?

[Richard J Kinch]

gibberdill writes:

> Also, I've heard elsewhere that calcium chloride should be *ADDED* to
> prevent metallic parts from corroding, or to someow maintain a balance
> of dissoled solids. Doesn't this contradict the idea of sequestration
> of calcium to prevent scale deposits?

Plaster pools need calcium to avoid etching the plaster, yet the calcium
must be limited to prevent deposition ("scaling"). The term "balance"
has a lot of casual (and misconceived) usage with regard to swimming
pools, but the "Langelier saturation index" is the genuine way to
understand the "balance" of calcium.

See my page:

http://www.truetex.com/poolcontrol.htm

Viz.,

"The Langelier saturation index is a formula based on pH, TDS,
alkalinity, and hardness, which predicts the degree to which water will
be corrosive, scale-forming (that is, precipitating solid calcium
carbonate onto surfaces), or neither."

You don't need to horse around with EDTA to prevent scaling, unless your
goal is to enrich the pool supply retailer.