Source: US Census. The median household income in the US is $50,502. This is some extremely useful data given that it is exploring over 114 million US households. If you want to know how most Americans are living this is a good figure to base your assumptions.
The myth that you have to wait 30 minutes or even an hour until you can swim after eating has been conventional wisdom for some time. The simple fact is, however, that swimming on a full stomach does not significantly impact your ability to swim.
To increase calcium hardness you'll need calcium chloride. Calcium Hardness. You can swim 2 hours after adding, but if you can, allow for one full turn-over of the water. A turn-over is a full and complete filtration of all of the swimming pool water, normally about 10 hours.