705.14.2 Solvent cementing.  Joint surfaces shall be clean and free from moisture. A purple primer that conforms to ASTM F 656 shall be applied. Solvent cement not purple in color and conforming to ASTM D 2564, CSA CAN/CSA-B137.3, CSA CAN/CSA-B181.2 or CSA CAN/CSA-B182.1 shall be applied to all joint surfaces. The joint shall be made while the cement is wet and shall be in accordance with ASTM D 2855. Solvent-cement joints shall be permitted above or below ground.
DOI Interpretation – purple primer shall be used on all PVC pipes. (June 2002 COCO)

(SEE:  Mecklenburg County Interpretation for Alternative Method inside the building finish.)

305.6 Freezing. Water, soil and waste pipes shall not be installed outside of a building, in attics or crawl spaces, concealed in outside walls, or in any other place subjected to freezing temperature unless adequate provision is made to protect such pipes from freezing by insulation or heat or both. Exterior water supply system piping shall be installed not less than 6 inches (152 mm) below the frost line and not less than 12 inches (305 mm) below grade.
DOI Interpretation – Water piping installed in a basement is not required to be insulated if approximately 50% of the basement walls are below grade, all openings are enclosed with windows and doors, and NO Garage Doors are installed in the basement walls. (June 2002 COCO)

802.2 Installation. All indirect waste piping shall discharge through an air gap or air break into a waste receptor or standpipe. Waste receptors and standpipes shall be trapped and vented and shall connect to the building drainage system. All indirect waste piping that exceeds 2 feet (610 mm) in developed length measured horizontally, or 4 feet (1219 mm) in total developed length, shall be trapped.
DOI Interpretation – is the length from the indirect waste to vent shall not exceed 25 feet as per Section 805.1.2 of the 1996 NC Plumbing Code.  (The maximum length of the indirect waste to vent was inadvertently omitted from the 2002 Code) (June 2002 COCO)

706.3 Installation of fittings.  Fittings shall be installed to guide sewage and waste in the direction of flow.  Change in direction shall be made by fittings installed in accordance with Table 706.3.  Change in direction by combination fittings, side inlets or increasers shall be installed in accordance with Table 706.3 based on the pattern of flow created by the fitting.  Double sanitary tee patterns shall not receive the discharge of back-to-back water closets and fixtures or appliances with pumping action discharge.
DOI Interpretation – The above would not apply to back-to-back water closets but would apply only to fixtures or appliances with pumping action discharge (clothes washer, etc). (June 2002 COCO)

421.2 Installation.  Whirlpool bathtubs shall be installed and tested in accordance with the manufacturer's installation instructions.  The pump shall be located above the weir of the fixture trap.  Access shall be provided to the pump.
DOI interpretation is that an access door large enough to remove motor and/or pump shall be provided at the side or end of the whirlpool bathtub (clearance of 21" minimum in front of the access door) and pump connections shall be within 15" of the access door.  The pump connections shall be toward the opening.  (June 2002 COCO)

Commentary Committee:
If the water heater (any gas appliance) is located out of the normal travel path no protection is required.  There are several ways to prevent vehicular damage to the water heater (any gas appliance).  These would include pipe bollards extending 3' (ft) above the floor, { 2" schedule 40 steel pipe set in concrete floor; 2" schedule 40 steel pipe set in cored hole in existing concrete floor and sealed with epoxy; 2" schedule 40 steel pipe with ¼" steel plate (welded) anchored to concrete floor with (4) ½" X 2 ½"  (embedment depth 2 ¼") anchor bolts}, curb stops and/or raised pads of not less than 5 ½" set not less than 40" from the water heater.

NCDOI/NCBCC Letters:

Residential Fixture Clearances (Click to download PDF)
Flammable Vapor Resistant Water Heaters (Click to download PDF)