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Plumbing systems are another aspect of new construction
and renovation projects that have stringent and complex code guidelines.
Again, while local codes and requirements may vary, most building
officials and inspectors make evaluations based on the National
uniform plumbing code; a highly technical, hard-to-read manual.
Many bookstores carry handbooks based on the National uniform plumbing
code, presenting material in layman’s terms; in an easier
to comprehend format.
To accommodate code variations from one local to the next, some
handbooks include three separate plumbing zones. Again, local codes
and requirements always supersede national code guidelines. Many
local building inspectors provide convenient summary sheets of applicable
code requirements for each individual project.
Most local authorities require a permit for plumbing projects; or
at least the plumbing phase of a larger project, requiring detailed
plans or drawings. At least three copies are usually required for
review; each must include a diagram of the water supply system,
and the drain-waste-vent system.
If code requirements are met, a permit is issued, granting legal
permission to begin work. An inspector will visit the work site
at or near completion of the project for final approval if all code
requirements have been met.
Meeting Guidelines
Calculating water distribution pipe diameter and length is complicated.
Each fixture comes with a “unit rating.” This helps
in calculating diameter and length needs. Some examples are toilet
– 3 units, vanity sink – 1 unit, dishwasher –
2 units, bathtub –2 units, and shower – 2 units.
The sum of unit ratings for all fixtures to be connected is the
“total demand.” In conjunction with the total length
of pipe from the street to the farthest fixture in the project,
this determines pipe diameter requirements. The size of pipe from
the street to the meter will also determine required diameters to
meet the demand.
Full-bore gate valves are required on the street side and house
side of the water meter, as well as on the inlet side of heating
system boilers and water heaters. All fixtures should have accessible
shutoff valves; this can include the ball valve type. All sill-cocks
should have individual control valves inside the house.
In many localities, water hammer arresters are required to prevent
pipes from rattling or vibrating when a fast acting valve is opened
on a fixture. Vacuum breakers are required in a system to prevent
any contaminated water from being drawn back into the system from
outdoor sill-cocks or branch pipes that run underground.
Because plumbing pipe is frequently routed through framing members,
there are restrictions as to what size holes or notches can be cut
in the various lumber sizes. For example, in a load-bearing 2X6-inch
stud, the maximum hole size is 2 ¼-inches, maximum notch
size is 1 3/8-inches deep. For a non-load-bearing 2X6-inch stud
the maximum size hole is 3 5/16-inches in diameter; maximum notch
size is 2 3/16-inches deep.
Drainage Pipes
In most areas, drain cleanouts are required at the end of each
horizontal pipe run. Individual fixtures require a minimum drain
trap size determined by the numerical fixture unit rating discussed
earlier.
There are also minimum horizontal and vertical drain pipe size
requirements. Again, these are determined by the sum of fixture
units that will feed into them. There are pipe support interval
requirements for both horizontal and vertical runs of pipe, determined
by length and pipe type; such as copper, ABS, PVC, CPVC, galvanized
iron, and cast iron.
Additionally, there are venting requirements; including pipe sizes,
critical distances, vent pipe orientation to drain pipe (upward
at no less than a 45-degree angle), as well as wet venting and auxiliary
venting size and distance requirements.
Finally, most localities have restrictions on which type of pipe
can be used for certain applications, such as type underground sewer
pipe running to a main sewer line or septic system.
Remember, for any project code requirement information, the local
building inspector is your best source, and the final authority
on meeting local requirements and final project approval.
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