Polyphosphates (and when
combined with a zinc source
is sometimes referred to as
bimetallic phosphates) have
been used in treating drinking
water supplies since the 1950s.
Orthophosphates (specifically zinc
orthophosphates) were first used in the
late 1960s by Long Beach, CA. As
polyphosphates will revert to the
orthophosphate form over a period of
time, the use of ortho/polyphosphate
blends has actually been going on for as
long a time as polyphosphates have been
used in treating potable water. It was
not, however, until the 1980s that some
vendors began intentionally adding
orthophosphate to a polyphosphate
source to market a blended product.
Today a full range of phosphate products with or without the addition of zinc
is available.