Hi Joe,
Be sure you read the large amount of S/H information on the Web site of the guy who invented it:
First Rays Semi-Hydroponics
Most people who grow in S/H use a very low concentration of fertilizer at every watering, with an occasional flush of pure water. I am having great success with this method.
I use Michigan State University (MSU) blend for pure water, 13-3-15 at 1/8 teaspoon / 0.625ml powder per gallon / 3.78 liter of rain water. This gives about 20 parts per million of nitrogen (ppm.)
I flush with rain or reverse osmosis water about once a month.
I'm not familiar with your fertilizer, but it has numbers on the label. You can figure out how much of your stuff to add to a gallon to get to your desired nitrogen concentration. Hint: A lot of S/H growers use around 20-40 ppm nitrogen.
There is also a fertilizer calculator on the First Rays Web site:
here.
2. Your water utility publishes their water report annually. You can find it online. You can read the TDS in your water. It varies dramatically across the US so you need to find out, and not hope.
Most orchids do well with 200 ppm or less, including the fertilizer. Phrags and a lot of cloud forest orchids should have much less than 200 ppm TDS. People in much of the eastern US can use tap water for orchids with no problem. Mine varies from 850-1200 ppm so I collect rain.