Jetter valves are special valve assemblies which allow to shut off one particular intake valve. The jetter valve cuts off the flow of one of the three pistons of the jetter pump. Due to this the pump starts pulsating which causes significant vibrations of the nozzle and an increased cleaning effect at a reduced flow rate (approximately -1/3 of the full flow rate of the pump). Jetter valves should not be combined with pulsation dampers in one jetter unit. Jetter valves substitute one of the three intake valves of a pressure pump (suction side (upstream). Never use jetter valves as a substitute on the high press side! Pulsation can be started or stopped by a lever or hand wheel at the jetter valve.