a visual difference in the output of the nozzles as more tension is applied to the spring. Be sure not to press down on the thumb wheel while turning it.
(3)Release the thumb wheel tension and, once again, there should be a noticeable change in the nozzle output.
C.The spring tension of the vacuum valve restricts the flow of water to the nozzles by changing the required amount of vacuum needed to operate the vacuum valve. Since the nozzles can only generate a fixed amount of vacuum (negative pressure) the flow rate of water is reduced which causes a finer spray and less output. If there was a vacuum leak in the water line it may not be noticeable with the vacuum valve spring tension set to zero, but it should become noticeable with greater tension applied to the spring. A good indication of a small leak would be very little visual difference in nozzle output while performing this test.
10-50
Page 40
