Does a heat pump alter water chemistry?

[Zaphod]

I finally tested for calcium. The reading is 20.

All my other water numbers are the same.

The heater will be installed next week. Any tips for what my target calcium number should be? If I need to increase, what do I add - and where do I get it? Is it a pool store chemical or is there a grocery store substitute?

[waterbear]

You can buy calcium increaser in the poolstore but if you can find DowFlake brand de-icer at a hardware store it is the same thing. If you go to the Dow Chemical website they list is as the product for increasing calcium in pools! I posted the url in a different thread but am not sure where in the foum it is buried now. The DowFlake is substantially cheaper than what you will pay at a pool store or even Walmart! Might be hard to find during summer, however.
I suspect that since Dow is one of the largest manufacturers of calcium chloride that most, if not all, of the calcium increasers sold for pools is just repackaged DowFlake! Bring your calcium up to about 150-250 ppm and run your TA at about 110-125 and you should be fine. (adjust TA first, test it after 48 hours and then adjust calcium)