Ways to Remove Fluoride from Water
Reverse Osmosis Filtration
This is used to purify several types of bottled water (not all), so some bottled waters are unfluoridated. Reverse osmosis systems are generally unaffordable for personal use.
Activated Alumina Defluoridation Filter
These filters are used in locales where fluorosis is prevalent. They are relatively expensive (lowest price I saw was $30/filter) and require frequent replacement, but do offer an option for home water filtration.
There are commercially available distillation filters that can be purchased to remove fluoride from water. On a related note: When looking at bottled water, keep in mind that 'distilled water' does not imply that a product is suitable for drinking water and other undesirable impurities may be present.
These Do NOT Remove Fluoride
Brita, Pur, and most other filters.
Some websites about fluoride removal state otherwise, but I checked the product descriptions on the companies' websites to confirm that fluoride is left in the water.
This will concentrate the fluoride rather than reduce it.
Freezing water does not affect the concentration of fluoride.
Steps to Reduce Fluoride Exposure
Don't take fluoride supplements.
Read labels on bottled beverages.
Unless they are made using distilled or reverse-osmosis water, they are probably made with fluoridated public water.
Consider using unfluoridated toothpaste.
Avoid drinking black or red tea.
There are many health benefits associated with chemical compounds found in tea, but this may be a beverage to avoid if you need to reduce your fluorine intake. Black and red tea come from two different types of plants, but both leaves naturally contain high amounts of fluorine.
Be wary of tinned fish and canned food items.
Fluoride may be used as a preservative.
Avoid black or red rock salt or items containing black or red rock salt.
Avoid using chewing tobacco.
Avoid long term use of medication that contains fluorine.
Certain antidepressants and medications for osteoporosis contain fluorine.