| Description | View of open trench with stopper in end of main; legend "Internal Cleansing of Main by General Descaling Co Shows the cut out in the main when carrying out internal cleansing operations. This is the end remote from the motor end and shows the method of connecting the hose pipe to the main with a tee piece in the supply so as to prevent excessive water pressure acting on the main or dirt from the main being sucked back into the water supply"; Ref M197; dated November 1948 |