The amount of water really does not matter. What does matter is what your orchids are growing in. I soak my (house) orchids for 5 or so minutes in a sink of tepid water (with 2 tbs. of fertilizer added), every week or two. They are growing in fast-draining potting medium, so as soon as I empty the sink, the water will have soaked the fir bark, coconut chips, and charcoal, but the excess water just runs out of their pots. I let them sit in the sink for several minutes before putting them all back on their bathroom window sill. Since the pots they are growing in, whether plastic or clay, sit in decorative orchid pots with built-in in saucers, the pots never sit in water. Having a bit of water in the saucers elevates the humidity around my orchids a bit.
