When I started an orchid hobby, I knew that I could not use Davis water. The water here contains 1000 ppm dissolved solids, and we have known for years that this severely limits our plants. I initially decided to use Whitehawk Ranch water from the mountains, where they do not put chemicals in the irrigation water. However, I found that this also had too many minerals in the water, and would restrict my plant growth.
So I purchased a Reverse Osmosis Portable System from firstrays.com, and I try to use it on the Whitehawk water, trucking the water back to Davis. I also have used it on the Davis water when necessary. When I started using this water, the plants responded immediately, and I noticed much better root growth. I also started using KelpMax with my MSU fertilizer, and this seemed to also prompt the plants to grow roots.