lovemytea wrote:they said the hardness/softness of the water was fine
fine for other things but maybe not tea
the hardness of municiple water varies greatly from place to place and there is no standard allowable limit. Basically anything that is >180-200 mg/l will give you scale to some degree in pipes or things used to heat water. There are many places in US that have hardness greater then 800mg/l.
Usually when there is a oil slick on tea it seems due to excessive minerals. Unless you are using those paper cups you get in coffee shops, in that case I think it is the thin coating of polyethylene resin they use over the paper(the stuff that makes it non-recyclable almost everywhere).
I'm not 100% sure this is true, but one theory is that calcium will bond with the fatty acids from the tea oils, too much calcium leads to a oily precipitate forming (the oil slick). Also the hotter the water the more this seems to form (possibly due to higher extraction of fatty oils?).
Another post above throws bicarbonate ions into the equation too. http://findarticles.com/p/articles/mi_m ... _14365029/
So....maybe you should consider...
1)a water softener
2)try a brita/pur/gravity filter (though I don't think this will be effective if your water is really hard)
3)buy bottled water
According to wiki...streams in Texas, New Mexico, Kansas, Arizona, and southern California have extremely hard water. Curious if you lived in that area.
I live in kentucky with hard water and have come across the oil slick issue too.