Expected ppm of RO water?

[RosieC]

As Gin has said, water softeners that use a salt are actually bad for orchids.

They work by replacing the calcium with something else (can't remember what now) and the thing they replace it with is even worse for you plants than the calcium.

RO water is used by a lot of folks on Orchid Board though, so if it is just an RO unit you should be fine.

[Ray]

Originally Posted by RosieC

As Gin has said, water softeners that use a salt are actually bad for orchids.

They work by replacing the calcium with something else (can't remember what now) and the thing they replace it with is even worse for you plants than the calcium.

Most water softeners replace the calcium-, magnesium-, and iron carbonates with sodium, and it is the excess NaCl that can be bad for plants. BUT... softened water is actually easier for an RO unit to clean than in the carbonate-laden tap water.

I think something is wrong with your RO unit (or meter), as you should not be seeing beyond the single digits on dissolved solids.