Doesn't like Kool-Aid
Join Date: Feb 2003
Location: Hawthorne, New Jersey
I think the RO unit should filter out the sodium, however that is not going to prolong the life of the membrane. In fact, it is going to actually shorten the life of the membrane. You are just replacing the calcium particles with sodium particles. Anything the RO membrane has to filter out is going to clog the membrane, there is no way around it.
Mixing RO and tap water is only going to add the sodium back into the water. I think the best bet may be to try and bypass the water softener and add unsoftened water to you RO. You need to find an RO:Tap ratio, but once you do it will be smooth sailing.