Where I live it's believed that local tap water is really bad for drinking because of the amount of limestone. As a science experiment for school I wanted to approximately calculate the percentage of calcium carbonate in tap water so I can make the conclusion: Is that amount of drinking $\ce{CaCO3}$ actually the problem or something else?
This question might be similar to DK4's question but I'm trying just to calculate not extract, only by using items you can find in a typical house (or in a local shopping center).
If calcium carbonate isn't the issue what is?
Edit: As pointed out in comments, percentage of $\ce{Mg}$ is also applied.