For much longer  hydraulic dump valve life, when there is any significant pressure across the valve, open it as quickly as possible.  This reduces the wear on the valve seats.  I would guess that most of our Dump Valves are quarter turn ball or plug valves and in this regard are better than a multi-turn gate type.  The flow surges the fluid system a bit, but the fluid system reservoir should stand it. I have one of original kit valves with many operations and no problems with the valve....Don Skeele  N320J      
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