12 May 2003
Including change 1, 19 January 2007
Sewer and Oily Waste Lines. A combination of electric heat tape and
pipe insulation should be used in accordance with Table C-4 for: (1) exposed gravity
sewer piping which drains fixtures directly; (2) exposed oily waste piping; and (3) those
portions of exposed pressure lines (sewage and oily waste) which will not drain
completely upon cessation of pumping. Neither insulation nor heating is required for
exposed sewer and oily waste piping (or portions thereof) which receive material
intermittently and which drain well when pumping stops. This applies to both pressure
lines and gravity lines.
Protection in Region V. In portions of region V in which the temperature
can drop below -4 degrees C (25 degrees F), use a properly sized flushing valve,
atmospheric thermostat, and timer to bleed approximately 132.5 l (35 gallons) per inch
of pipe diameter for each 30.5 m (100 ft) of fresh water pipe. This flushing is to be
applied over an 8 to 12 hour period on each day that the ambient temperature drops
below 4 oC (25 oF). Pipes need not be insulated, but flushing valves and connections
must be located at system extremities and must be protected from freezing.
Modification of Requirements for Saltwater. Because seawater
freezes at a temperature approximately -15.3 oC (4.5 oF) lower than that at which
freshwater freezes, make the following adjustments when designing freeze protection
for exposed saltwater mains:
In regions I and II, treat saltwater the same as required for freshwater.
In region III, design as for region IV.
In region IV, design as for region V.
In region V, no freeze protection is necessary for saltwater at any location.
Pipe. Piping materials must be metallic where heat tape is required.
Where a flushing system is utilized, any approved piping material may be used.
Heat Tape. Flat style electric heat tape is recommended. Heat tape
should be easy to splice and repair and must be waterproof. A low watt density (4 to 10
watts per lineal foot of pipe) is recommended, and the ability to lap the tape without
damage should be required. When heat tape is used with the insulation thicknesses
listed in Tables C-2 and C-4, they will cycle 30 to 60 percent of the time on the coldest
Insulation and Covering. Closed-cell foam-type insulations (such as
cellular glass) having low moisture absorption qualities should be used for Regions I
and II due to the destructive effect of freezing on wet insulations. Use closed-cell foam-
type insulation for regions III and IV if wave action and/or immersion are possible.
Cover all insulation with a watertight metallic or plastic system.