The Blending Valve Panel ...
Published by Ronald Gamble, General Contractor at home
The Blending Valve Panel (BVP-1) was developed for use with high-pressure humidity control systems as an effective and economical alternative to Reverse Osmosis (RO) water pre-treatment systems.
The Blending Valve Panel is designed to be used in conjunction with DI tanks for blending Deionized (DI) water with your raw supply water producing a desired water quality output in parts per million (ppm) of total dissolved solids (TDS).
http://www.industrialairtreatment.com/library/humidification/water-treatment/blend-valve.pdf