1. Check the position of the water heater to
make certain the pipe from the meter will
connect to the inlet of the water heater. Once
the water heater is in position, installation of
the cold water pipe can begin. There are two
options for connecting the water heater to the
water lines: rigid pipe (as shown) or flexible
connectors (copper or braided stainless
steel). Rigid pipe and unions require more
precise work because the unions must align
and the length of the vertical pipe must be
accurate.
2. One way to determine where the 3⁄4 × 1⁄2 × 1⁄2
reducing tee must be located is to install an
MIPT in the water heater inlet and extend a
short length of 1⁄2″ pipe vertically to the point
where it crosses the 3⁄4″ horizontal pipe. Hold
the reducing tee in position beside the verti-
cal pipe and mark the 3⁄4″ horizontal pipe at
the right of the fitting. Add the appropriate fit-
ting allowance and cut the 3⁄4″ pipe to length.
3. Temporarily install the 3⁄4 × 1⁄2 × 1⁄2 reducing tee
and work downward to the water heater. The
exact location of the ball valve and union is
not critical. However, the total length of the
assembly and the alignment of the union
components must be accurate.The handle of
the ball valve should be far enough from the
floor frame to provide clearance for operating
the valve.
4. Once the ball valve is installed, cut a short
length of pipe, assemble the union, and tem-
porarily hold the pipe and union in position.
Measure the face-to-face dimension between
the union and the MIPT adapter. Add the
appropriate fitting allowances and cut the last
piece of pipe. Check alignment and perma-
nently assemble these components.
5. The installation of the hot water pipes is
essentially the same. The horizontal runs of
pipe leading to the kitchen/laundry and bath-
room areas will be secured to the underside
of the floor joists. Therefore, the height of the
90° ell will be determined by the position of
the 1⁄2″ horizontal pipes. Temporarily place a
1⁄2″ tee on a length of 1⁄2″ pipe and attach it to
the underside of the floor joists in position to
go to the bathroom area. Place a length of 1⁄2″
pipe in the MIPT adapter in the outlet of the
water heater. Plumb the pipe and hold a 90°
ell in position so the face-to-face distance
between the 1⁄2″ tee and the 90° ell can be
measured. Add the fitting allowance and cut
the pipe.
6. Temporarily install the 90° ell and cut a length
of pipe to join the union to the ell. Hold the
assembled union in position on the pipe and
measure the face-to-face distance between
the union and the MIPT adapter. Add the fit-
ting allowances and cut the pipe. Make a trial
assembly of the components and check
alignment before making the assembly
permanent.
7. The T/P relief valve is installed using Teflon™
tape to ensure a watertight joint. The dis-
charge pipe must be the same nominal diam-
eter as the outlet of the T/P relief valve. It ter-
minates above the floor drain — an air gap
above the floor of more that 1″ but less than
6″ must be maintained.
8. The runs of 1⁄2″ cold and hot water pipes that
go to the bathroom and laundry/kitchen area
can be installed following similar procedures.
It may be desirable to temporarily extend a
length of pipe for each of the runs from the
water heater, then start at one of the fixtures
and work backward to connect with the cor-
rect branch.
The short lengths of pipe directly connected
to the water heater must not be PVC. CPVC
may be acceptable, but copper or galvanized
iron pipe is often preferred. If the water heater
were to overheat, the high temperature of the
water may cause the plastic pipe to fail at this
location and even at the cold water inlet pipe.
352
Section 3 Plumbing System Design and Installation
Neither check valves nor shut-off valves
should be installed in the discharge piping
from a water heater.
Code Note
Joints between copper and galvanized
pipe should be made with dielectric fittings to
prevent corrosion.
Code Note