A tapping sleeve and valve allows access to and branching off of an existing water main. A Tapping Sleeve and Valve differs from an ‘Inserting Sleeve and Valve’ in that it does not allow closure of the mainline, only closure of the branch being added by way of the new valve.
The word ‘tapping’ refers to penetrating the existing water main. 2 types of taps can be done on an existing water main:
-A standard tap done on an existing main not in operation, often done after closing nearby valves isolating the section being worked on.
-A live (aka ‘wet’ or ‘hot’) tap when the existing main remains in operation.
An example of when a standard tap might be done is when the section to be tapped can be isolated with existing valves and no other branches/services exist on the isolated piece. However under these conditions, engineers may also choose to simply have a ‘Cut-In Valve’ installed. A ‘Cut-In Valve’ involves cutting the main and installing a new tee, valve, and branch line. The isolated section of main may require bacteria and pressure testing before reopening.
The benefit of a live tap however is avoiding loss of water services to residences or businesses that would have otherwise been shut down due to a section of the main line being shutdown. This also avoids the need to pressure test or bacteria test an existing watermain in use.
Tapping sleeves are typically made of primarily stainless steel and aside from the bolts/etc, are typically two piece assemblies. The first piece will have a flange on it (for connection to the gate valve) and will be attached to a rubber gasketed saddle which will ultimately be placed over the existing pipe. The second piece will attach to the gasketed saddle on the opposite side of the pipe being attached to. The bolts are then tightened to the appropriate torque.
The gate valve is then lowered into the trench and installed flange to flange with the tapping sleeve by way of gaskets and megalug/s.
After the gate valve has been bolted and appropriately torqued onto the tapping sleeve, the tapping process can begin. The gate valve will be placed in the open position so the tapping drill can pass through and the drill is then attached to the valve assembly. The mainline is then cored into allowing water to pass into the gate valve and into the drills water chamber. The drill is then pulled back past the valve and the gate valve is placed in the closed position so the drill can be removed.
Then whatever is planned next for the mainline branch can be attached to the gate valve.