Bill, when you make a connection off the fire hydrant, remember to open the valve completly. Hydrants only seal completly at the fully closed or fully open position. If you partially open the hydrant, you will be flushing water out the bottom. If you need to lessen the flow of water, use a gate valve. When closing the hydrant, put your hand over the open port. When the hydrant is completly closed, the drain at the bottom will be open and you will feel the vacuum, indicating the hydrant is properly drained. Improper operatioin of a hydrant can lead to the hydraant being washed out at the bottom, not completly drained and frozen hydrants. Most fire departments don't like untrained people opening and closing their hydrants. I know we never did.
Douglas Hicks
General Fire Equipment Co of Eastern Oregon, Inc