Underfloor (Sanitary Plumbing)


The residential inspection checklist for underfloor (sanitary plumbing) includes:

  • Materials in compliance with section P3002, I.R.C.
  • Building sewer test: a minimum 10 foot head of water / minimum 15 mins., section P2503.4, I.R.C.
  • Drainage piping and fittings to maintain 2% grade slope (1/4 unit vertical in 12 units horizontal), section P3002.3.1, I.R.C.
  • Drainage fittings and connections, section P3005 and Table P3005.1, I.R.C.
  • Approved two-way cleanout, section P3005.2.7, I.R.C.
  • Approved cleanout at base of waste or soil stack, section P3005.2.6, I.R.C.
  • Additional cleanouts - use the "135 degree" rule (City standard) in lieu of the "more than 45 degree/40 foot length" rule, section P3005.2.4, I.R.C.
  • Additional cleanouts - each 100 feet, section P3005.2.2, I.R.C.
  • Backfill material shall be free of rocks, broken concrete and debris until pipe is covered with at least 12 inches of tamped earth, section P2604.3, I.R.C.
  • Over-excavation must be replaced with compacted earth, sand, fine gravel to provide solid/continuous load bearing support, section P2604.1, I.R.C.
  • Trap arm length from vent per Table P3105.1, I.R.C. ( 1-1/4" is max. 5 feet, 1-1/2" is max. 6 feet, 2" is max. 8 feet, 3" is max. 12 feet and 4" is max. 16 feet).
  • Maximum three (3) water closets on 3-inch drainage pipe (City standard).
  • A "sanitary tee" fitting is only allowed to be used when changing from the horizontal to vertical direction, Table P3005.1, I.R.C.
  • Every dry vent connection to a horizontal drain shall connect above the centerline of the horizontal drain pipe, section P3104.3, I.R.C.
  • Vent sizing shall comply with section P3113.1, I.R.C.
  • Deadends shall be prohibited except when necessary to extend a cleanout, section P3005.1.5, I.R.C.
  • Cleanout shall be installed not more than 100 feet apart in horizontal drainage lines measured from the upstream entrance of the cleanout, section P3005.2.2, I.R.C.