Question

Why are two gate regulators necessary in regular practice to form washout regulators?

Answer

In fact, situation is analogous to that of fire hydrants in that two gates valves are installed with a on its own fire hydrant. Washout valves are used for regular maintenance work of watermain like allowing flowing out of water throughout cleaning of watermain. At junction anywhere a tee-branch out to a washout point, a gate valve is installed to divide two pipelines. However, this gate valve is open throughout normal operation as another gate valve further downstream is installed. If downstream gate valve is not installed in position, then pipe section of branched-out watermain will be left dry during normal operation and there is a high probability that break to watermain and frequent leakage would happen. With downstream gate control device installed, segment of branched-out watermain consists water in regular operation. In a case there is any leakage, it be able to be readily detected by using two gate regulators.