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Tapping of a pressure pipe is a critical and necessary operation for the installation and continued operation of a pressure pipe system. Tapping is the process of adding a branch line to a previously installed pressure line.
There are four basic categories of tapping:
2.1 Direct Tapping
Direct tapping is the method of installing the branch tap directly into the pipe wall. In this method the shut-off valve, or corporation stop, is threaded into the pipe wall. The added step of cutting the threads adds a level of difficulty to this method.
Underground Solutions does NOT recommend direct tapping into Fusible PVC®.
2.2 Saddle or Sleeve Tapping
In this method, the pipe to be tapped is supported by a tap saddle or sleeve. The saddle/sleeve contains the threaded connection for the corporation. This results in only a smooth bore needed into the tapped pipe. The saddle/sleeve is sized to fit the PVC pipe exactly, and is made specifically for use with PVC pipe.
Underground Solutions requires the use of either a saddle or sleeve made specifically for PVC pipe when tapping Fusible PVC®.
2.3 Wet Tapping
This is the method of installing the tap while the line is under pressure. This means that the line can stay active and does not need to be drained. A tapping valve is installed on the sleeve/saddle to allow shut off of pressure once the tap is made.
Fusible PVC® IS able to be wet tapped.
2.4 Dry Tapping
This is the practice of tapping the pipe while not under pressure or full of liquid. With the line empty (or "dry"), the tapping is made and then pressurized after the tap is completed.
Fusible PVC® IS able to be dry tapped.
Tapping machines normally come in two types: Manually driven machines for 1" and smaller saddle taps, and motor driven machines for larger taps. There are many manufacturers of taps machines, and some will perform better than others.
In the 3/4" to 1" tap size, a PVC cutter bit must be used. Both Reed Manufacturing and Mueller Co. make good quality tapping machines and bits in theses sizes.
For the Reed tapping equipment, Model DMPVC or DM2100 have proven to work well on PVC when using the proper cutter. Reed manufactures a PVC cutter for a standard 3/4" and 1" corporation. The Reed catalog # is PL688 and the item # is 04385.
Fusible PVC® IS NOT TO BE tapped with hand held drills using wood drill bits or hole-saws.
Reed has various combinations of tap machines as noted below. The critical feature is the proper PVC cutter tool. While older models could likely work properly with PVC, it is important to consult with the equipment supplier to be sure that the PVC cutter bits are adaptable to the bit connection or arbor. If there is any question regarding the applicability of the PVC cutter tool, please contact your Underground Solutions, Inc. representative.
The Mueller CL-12 is the preferred machine for taps larger than 2". This is primarily because of the PVC cutter bits available. Other machines with large diameter capacity do not have PVC cutter bits but rely on hole saws or standard metal bits to cut PVC.
The shell cutters and parts indicated above fit directly to the CL-12 arbor. They can also be adapted to larger Mueller tapping machines with additional arbor adapters.
Figure 5.1 - Typical PVC Tapping Saddle
Tapping saddles are used for the installation of a corporation stop in a tapped pipe. Typically this is done on pipe sizes in the 4" to 12" range. The tap saddle is made to a specific inner diameter to match the outer diameter of the pipe. It fully supports the pipe and is sized so that the parts when bolted together cannot be over tightened on the pipe. Manufacturer's installation instructions must be followed. Tap saddles do not have U-bolt type configurations that do not adequately support the pipe. Tapping saddles MUST BE DESIGNATED FOR USE ON PVC PIPE.
An example of manufacturer's materials description for tap saddles follows:
Tap sleeves are used for larger diameter taps and larger diameter pipe. The sleeve is a two part assembly that bolts together and grips the pipe to be tapped. Because of this, the installation is different than the tap saddle. The bolts must be installed per manufacturer's torque requirements. The tap sleeve can be over-tightened placing excess stress on the pipe and tap. Over-tightening MUST BE AVOIDED for the tap sleeve to function properly.
Tapping with a hand operated tap machine using a tap saddle, the following steps are normally followed:
When tapping a larger diameter pipe, tap sleeves are used and in most cases are used with a power operated tapping machine. The tap machines can be operated by hand, air motor, or hydraulic pump. The manufacturer's instructions must be followed. The steps to be followed are:
The tap coupon should have a smooth straight side wall when removed from the tap machine. Rough side and the presence of striations are indications of a poor tap.
Figure 9.1 - Illustrated Tap Results