Mash the blueberries a layer at a time in something like a pie plate using something like a potato masher.
Add to a large pot.
Add lemon juice to pot.
Add the calcium water to the pot.
If using sugar or Splenda, put them in a bowl, add the pectin powder, and mix. If using a liquid sweetener such as honey or liquid stevia, ladle out about 4 tablespoons of juice and put in a small bowl. Add the pectin powder all at once, and stir it into juice. Whatever combination you used, set it briefly aside.
Bring the pot to a boil over high heat.
Add the pectin mixture a little at a time, stirring constantly.
Let boil vigorously for another 2 minutes, stirring constantly.
Remove from heat.
Ladle into 125 ml (4 oz) or quarter-litre (½ US pint / 8 oz) jars.
Leave 1 cm (¼ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process either size jars for 10 minutes; increase time as needed for your altitude.
Notes
Sweetener suggestions: 1 cup (200 g) sugar or 1 cup (25 g) granulated Splenda OR ½ cup up to 1 cup (125 to 250 ml) honey or 2 teaspoons liquid stevia.