Calcium Hardness

[Vinny]

I think that a blanket statement of calcium is good or bad is a wrong type of statement. Can anyone say that all tubs has a ss heater, or won't be affected by low calcium - I would think the answer is no.

Repeat_Offender's tub manufacturer recommends it, Taylor recommends it for balancing purposes and to keep foaming down but that doesn't mean that everyone has to or should add it.

My opinion is that I add it for the water balancing purposes. I have read that heater could be affected but have no proof. It is very probable that a heater is erroded by low PH. We have people on here that haven't used calcium and apparently are fine, I use calcium ... it's MY N2 cartridge!

[The_real_Clown_Shoes]

A thin coat of scale is the best thing you can ask for in your spa heater.  

Also the Saturation index.

[Bill_Stevenson]

Calcium is needed if the water is very soft.  Soft water results in lots of foam.  Hard water does not foam.  If you have no foam, you should relax and not worry.  
 
This is the same as how soap works in the shower.  Hardwater results is the soap not lathering up well, and also being difficult to rinse off.  For showers soft water is better.  For spas hard water is better.
 
Anyone who claims that not adding calcium to the water will cause spa parts to be ruined is a charlatan and you should run like hell to get out of their store.
 
Bill

[Tman122]

Summary;

Use calcium increaser if you feel you need to because of foam or a manufacturers/dealers recommendation.

Don't use calcium increaser if you don't feel the need and have no limitations from your manufacturer/dealer

If you do use it, don't for a water change and see if it makes a difference.
If you don't use it, do for a water change and see if it matters.

Ya got nothing to loose. And probably have nothing to gain.

[IDW]

I am not a chemist, so forgive me if what I say is not totally exact.

2 reasons for calcium hardness:

1.  Soft water foams.  Often foaming issues are really soft water issues, not from lotions, soaps, etc.

2.  You Taylor Test Kit fans should know this one (unless they have changed their instructions and support documents).  Water balance is the relationship of at least 4 factors, temperature, pH, TA and Calcium Hardness.  If your hardness is low, then, according to the Langlier (sp?) index the industry uses, your pH and TA have to be adjusted accordingly.  pH bounce could be the result, as you would think your TA is in range, but it really isn't.

Does this begin to answer the question?

Yes it does. Well done non chemist!!!