# Making hard water

Does anyone know how to make hard water with a hardness of 200+ ppm in terms of $$\ce{CaCO3}$$?

I live in Seattle and we have very soft water and we need hard water for testing purposes. Obviously you cannot dissolve $$\ce{CaCO3}$$ in water. I've read many "recipes" even ones that claimed you can dissolve $$\ce{CaCO3}$$ with a soda stream pop maker. Best I could do was a 60 ppm.

I've tried baking soda and Epsom salt and was able to make 130 ppm.

I've tried $$\ce{HCl}$$ to dissolve it in water, but the resulting pH was not suitable and if I tried to raise the pH, the $$\ce{CaCO3}$$ precipitated back out of the water.

I'm at a loss on a "recipe" that actually works. Am I trying to replicate the possible? Any ideas?

• You might want to read Sources of hardness on Wikipedia. It's not about just carbonates, you actually want to have soluble bicarbonates (and other anions such as sulfates and chlorides, for completeness) in solution. – andselisk Apr 15 at 1:57
• Andselisk,Thank you for taking the time to respond. Yes I've read about sources of hardness. Allow me to explain what I'm attempting to do. I am trying to replicate the formation of hard scale. I have a clear understanding of how to get CaCo3 to precipitate out of solution. (Pressure, pH or raise in temperature) what I'm lacking is a recipe to create a solution that will precipitate CaCo3 in the form of hard scale. Only thing I can think of trying is Calcium hydroxide and bubble Co2 through it. – Jason Rusk Apr 15 at 3:41
• What about some calcium bicarbonate rich mineral water ( composition is usually provided ), diluted to desired concentration ? – Poutnik Apr 15 at 4:23
• @JasonRusk, what andselisk says is correct, but I'm not sure you understood correctly. "Hard scale" as you call it does not just consist of carbonates (and calcium), it is also composed of magnesium salts and both with chlorides, sulfates, etc. So, you need to make a mixture. What you are referring to or trying to get around sounds like just calcium carbonate solubility. I'm unsure why you are using CaCO3 - are you referring to the equivalent unit 'mg CaCO3/L'? That is not to be taken literally...best to convert that to mg/L Ca and Mg and choose a few different salts from those. – prof.kvothe Apr 16 at 12:08
• I think hard scale might occur only slowly. Fast precipitation tends to make smaller crystals and many of them. – James Gaidis Apr 16 at 16:41