Mark Cooper wrote:
I picked up a floating hydrometer and I'm wodering if they are affected by
barometric pressure? When I float it in RO water it reads 1.004. Since I'm
located in Iowa, which is above sea level a bit, will this affect the
reading a bit?

http://en.wikipedia.org/wiki/Elevator_paradox_(physics)

It shouldn't be affected suggesting that it is either miscalibrated or
that your RO water is rather "heavy." How about temperature?

-K