location of pipe A makes it possible to begin
with the hot water riser to the tub/shower
valve, Figure 20-9. The riser (B) is the vertical
part of the branch to the tub/shower valve. The
tub/shower valve is installed during second-
rough because it is inside the finished wall. A
variety of different tub/shower valves are
available, and it is necessary to refer to the
manufacturer’s directions for installation
details. Most tub/shower valves are fitted with
a round plastic guide that is installed flush
with the finished wall. The finished wall mate-
rials are fitted around the guide. The guide is
removed during the finish stage of plumbing
installation providing an opening in the wall in
front of the valve so that the valve can be
adjusted and repaired. A removable metal
cover closes the opening in the wall and the
knob is installed during the finish stage of
plumbing installation.
Tub/shower valves have connections for
four pipes: one each for hot and cold water,
one for the showerhead, and one for the tub
spout. It is very important that the valve be
positioned properly. If, for example, it is
installed upside-down, the showerhead may
not receive enough water to work properly and
the water temperature controls may not work
properly. Check the valve for markings that
indicate the correct position. Tub/shower
valves are generally installed about 36″ above
the floor, so that a person both seated in the tub
and standing at the shower can reach the
control. Check the rough-in dimensions. It is
critical that the blocking be installed the correct
distance from the face of the studs so that the
plastic guide on the valve is flush with the
finished wall. Again, check the manufacturer’s
directions before installing the blocking.
Most tub/shower valves require that MIPT
adapters be threaded into the four openings so
that pipes can be connected. Teflon™ or pipe
joint compound must be used to make these
joints watertight. If copper pipe is being
installed, exercise care to prevent heat from the
soldering operation from damaging internal
parts of the valve. The manufacturer may
recommend removing some of the internal
parts of the valve. At a minimum, solder the
adapter to the pipe before threading the fitting
into the valve. When soldering the tees in the
water pipes, wrap a wet cloth around the
adapter to keep it and the valve cool.
358
Section 3 Plumbing System Design and Installation
Figure 20-9. Tub/shower valves are installed during
second-rough because they are inside the wall cavity.
B
Drop ear ell
with FIPT
outlet for
showerhead
Hot water
Cold water
Tub/shower
valve w/
plastic guide
Tee
Air chamber
Cap
MIPT adapter
Drop ear ell
with FIPT
outlet for
tub spout.
Blocking
Stud
Sole plate
Tub/shower valve: Valve fitted with a round plastic
guide that is installed flush with the finished wall
during the second-rough stage.