trying to diagnosis a water hammer which i havent yet had the opportunity to hear. client initially stated that the system has a crash noise when turned on, thinking odd- i asked if they were sure if the cash happened when system is turned ON or OFF. Client replies that they're not sure, it just happens at in the early morning hours i did a mainline repair on what happened to be a long stretch of higher-than-the-rest elevated pipe, could it be trapped air? on a possibly unrelated note: dv-100, in your opinion, is it fast or slow-closing? and In relation to the dv-100 will a toro 260 close more slowly under the same variables?