[Ian Lancaster]

Passing it too quickly through the resin?

ian why would it pass too quickly?

If you use a booster pump it may push the water through very quickly.  This is OK for the RO because the contamination is stopped by the membrane, but resin works by absorbing the contaminants onto the surface of the resin beads.  If the water is flowing too quickly through the resin, it doesn't have time to work, so doesn't remove all the contaminants.

[telfordwindowclnr]

Contact doug Atkinson. He is the grandaddy of DI resin issues, he will give you the best advice.