excess will bead out on the surface of the face of the
fitting and can be easily wiped away.) Immediately,
upon finishing the cement application, insert the pipe
to full socket depth and rotate one fourth of a turn to
ensure complete distribution of cement, as shown in
view D, figure 3-27. Hold the pipe together for 10 to 15
seconds, so it does not move out of its socket. After
joining, immediately wipe the excess cement from the
pipe and fitting and gently set the pipe on a level
surface. Do NOT move the pipe for about 2 minutes.
(As the pipe size increases, it takes longer for the joint
to set up.) The pipe SHOULD NOT be joined in
temperatures below 40°F and above 90°F or when it is
exposed to direct sunlight. The drying time should be
at least 48 hours before the joint is moved or subjected
to internal or external pressure. The drying time is
shorter in hot weather and longer in colder weather.
DO NOT ATTEMPT TO SPEED THE SETTING OR
DRYING OF THE CEMENT BY APPLYING HEAT
TO SOLVENT-WELDED JOINTS. Forced rapid
drying by applying heat causes cement solvent to boil
off, forming bubbles and blisters in the cement film.
During cool weather, the setting of the cement can be
speeded by prewarming the cement, the pipe, and the
fitting, or by shielding the joint from the wind.
CHECK THE SHELF LIFE OF THE CEMENT. Do
NOT use cement that is lumpy or stringy. Do NOT try
to thin it out with a thinner or primer. Always follow
the instructions on the cement container; the above
estimates should in no way be used in the place of
Fusion welding requires either a gas- or an
electric-heated welding tool, as shown in figure 3-28.
As the tool warms up, spray its contact surfaces lightly
with a silicone-releasing agent (view A, fig. 3-28).
This prevents the pipe from sticking to the surface of
the welding tool. Check the temperature of the tool.
Ensure the tool reaches the proper temperature range
(view B, fig. 3-28) before placing the pipe on the
heating element. Be sure the pipe is squarely on the
element. Hold onto the pipe, as shown in view C, figure
3-28, until a bead appears on the pipe at the entrance of
the female tool piece. After the bead appears, remove
the pipe and insert it into the fitting, squarely and
completely, as shown in view D, figure 3-28. DO NOT
ROTATE THE PIPE WHILE IT IS BEING JOINED
WITH THE FITTING. After joining, clean the fusion
welding tool, as shown in view E, figure 3-28.
In fillet welding plastic pipe, as shown in figure
3-29, maintain uniform heat and pressure on the rod
while welding. Too much pressure on the rod stretches
the bead and causes the weld to crack, as it cools. The
rod should be held at a 90-degree angle to the joint. The
rod bends in an arc when proper pressure is applied.
When finishing a weld, make the bead overlap the top,
NOT alongside itself, for at least 3/8 to 1/2 inch. Never
overlap alongside when welds are being spliced.
Threaded plastic pipe should be used only as a
temporary piping system. Threading reduces the wall
thickness and results in lower pressure ratings. Only
schedule 80 or heavier pipe should be used when
plastic pipe is being threaded. Never use pipe
wrenches to tighten threaded pipe; use a strap wrench,
as shown in view A, figure 3-30. Be sure to use an
insert within the vise jaws to prevent scoring of the
pipe. Use a wood or aluminum plug while the pipe is
being threaded to prevent distortion of the pipe and to
avoid off-center threads, as shown in view B, figure
3-30. The dies should be sharp; and for best results
with power tools, use a 5-degree negative front rake.
When tightening threaded joints, avoid too much
torque. One or two turns past hand-tight is sufficient.
Teflon tape should be used as a pipe joint compound.
PLACING PLASTIC PIPE IN THE
GROUND.On hot days, after the plastic pipe has
been cement solvent welded, it is a good idea to snake
the pipe beside the ditch or if the ditch is wide enough,
in the ditch during its required drying time. DO NOT
APPLY STRESS or DISTURB A JOINT THAT IS
DRYING. Snaking gives added length to the pipeline
to compensate for thermal contraction, as the pipe
cools. When the temperature change is less than 30°F,
not necessary. When cement solvent
welding on a hot, summer day during the late
afternoon, be sure to snake the line. Since the pipe
Figure 3-29.Fillet welding plastic pipe.