Direct Taps should be carried out in the following
temperature ranges:

i) Ambient temperature in the working anvironment

Minimum Max imum

Ory Taps -189C 45°C

ii) P.V.G. pipe temperature

Dry Taps -189C 38°C
Wet Taps 0°C 32°C

The Research and Engineering Division of Manville have
carried out extensive research on the direct tapping of
P.V.Ce pipe. The conclusions reached are as follows:

1. Corporation stops subjects to axial or circumferential!
stresses will teak around the threads with a few
hundred kilograms applied force.

Corporation stops subjected to direet radial (r) pull
aormally will not leak below 450 kg pull. .

Corporation stops subj ected to axia! or circumferential!
pull will normally jleak around the vaive before leaking
around the threads. Valve feak is usually much more
severe than thread leak. ,

Teflon tape applied to the corporation stop threads is
of significant value in preventing laaks.

Application of Teflon also reduces the torque required
to in art the stop from 95 joules (70 ft-Ib) to 41
joules (30 ft-!b). Two to three threads should be jeff
showing above the pipe wall.
* .

In servica, a goose neck is normally installed between
the corporation stop and the service line. This
reduces the possibility of large forces being.applied

to the fitting.

The ability to withstand forces without leaking
increases with pipe diameter and wall thickness.

From the studies carried out by Manville, it appears that

direct tapping of P.V.C. pipe for i9 and 25 mm connactions
is acceptabia provided Teflon tape is utilized on *he
corporation threads. Pull out of the corporation stop
undar field conditions has not been directly answered by
the research, but based on the results of the "Pull out fo
Failure!" tests, It would appear that the service connection
tubing would pull out of the corporation before a pipe

-falture would occur.