Physics of Buildings

Sources and simplifications

Every reference cited on this site, and every place a figure idealizes the real system.

References

  1. Samuel J. Ling, Jeff Sanny and William Moebs (2016). University Physics Volume 1, §14.2 Measuring Pressure and §14.6 Bernoulli’s Equation. OpenStax, Rice University. textbook §14.2: a manometer column of height h balances a pressure difference hρg; gauge vs absolute pressure. §14.6 (https://openstax.org/books/university-physics-volume-1/pages/14-6-bernoullis-equation): p + ½ρv² + ρgh = constant along a streamline; pressure drops where a fluid moves fast. (How traps lose their seal)
  2. John L. French and Herbert N. Eaton (1951). Self-Siphonage of Fixture Traps, Building Materials and Structures Report BMS 126. National Bureau of Standards, Washington, DC. government research report Foreword: the water seal is normally 2 to 4 inches deep; lost seal lets drainage-system pressure fluctuations bubble sewer air back through the trap. §1 fig. 1: definitions of trap weir, depth of seal, remaining seal, seal loss; siphonage by other fixtures vs self-siphonage. §2: inertia of the water at the end of the discharge, air bubbles dragging water, the inlet leg pulled down to the dip so air passes; refill by trail discharge. §5.2: discharge set by orifice, trap, drain and vent fitting. (How traps lose their seal)
  3. Ambler Thompson and Barry N. Taylor (2008). Guide for the Use of the International System of Units (SI), NIST Special Publication 811, Appendix B.8. National Institute of Standards and Technology. standards body inch of water, conventional = 249.0889 Pa; psi = 6894.757 Pa. (How traps lose their seal)
  4. Gary Gauthier, Building Safety Journal (2025). Code Corner: 2024 International Plumbing Code Chapter 9: Vents. International Code Council. code body article IPC 901.2: vent piping permits the admission or emission of air so the pressure difference across a trap seal stays within 1 in. of water column; positive pressure pushes a seal back, negative pressure pulls it over the weir; §1002.4 has provisions for traps subject to evaporation. (How traps lose their seal)
  5. IAPMO (2018). Uniform Plumbing Code (2018), Chapter 10: Traps and Interceptors (Nevada adoption, printed copy). IAPMO; copy hosted by the City of Lynnwood, WA. plumbing code 1002.1 every trap protected against siphonage and back-pressure by a vent; 1002.2 trap arm length limits (table); 1002.4 vent opening not below the trap weir; 1004.1 S traps, bell traps and crown-vented traps prohibited; 1005.1 liquid seal 2 to 4 in.; 1007.1 trap seal primers for infrequently used floor drains. Described, not reproduced. (How traps lose their seal)
  6. Robert S. Wyly and Herbert N. Eaton (1961). Capacities of Stacks in Sanitary Drainage Systems for Buildings, NBS Monograph 31. National Bureau of Standards, Washington, DC. government research report §4.5: vents are sized to hold pneumatic pressures within +1 to −1 in. of water column of atmospheric, so pressure effects on trap seals are negligible; vent sizes for a 1 in. drop computed with Darcy–Weisbach plus loss coefficients. §7: vent stacks sized so pressures do not destroy trap seals. Measured air-to-water flow ratios in a stack. (How traps lose their seal)
  7. J. A. Swaffield and L. B. Jack (1998). Drainage vent systems: Investigation and analysis of air pressure regime. Building Services Engineering Research and Technology 19(3): 141–148. doi:10.1177/014362449801900305. peer-reviewed paper Abstract: knowledge of vent performance and trap seal loss and retention has grown from research into the generation and propagation of air pressure transients; experimental tests on several single-stack systems (stack diameter, roughness, height, water flow) give expressions for the pressure regime at critical points. (How traps lose their seal)
  8. J. Pickering Putnam (1911). Plumbing and Household Sanitation (chapter: The Siphonage and Evaporation of Traps). Doubleday, Page & Co.; reproduced at chestofbooks.com. historical text Reports evaporation experiments signed June 1884 (Putnam and Rice): about 1/7 in. a day in traps vented 3 in. past the crown, over 1/3 in. a day with the vent at the crown; fastest in winter and with heated flues, slowest in damp summer weather; a 1¼ in. S-trap seal lost in four to eleven days. (How traps lose their seal)
  9. Union Sanitary District (2024). Prevent and Report Odors. Union Sanitary District, Union City, CA. public utility A dry trap is the most common cause of sewer odors indoors; every shower, tub, floor drain and toilet has a trap; when the trap is dry, odors may enter the building. (How traps lose their seal)
  10. Colorado State University Pueblo, Environmental Health and Safety (2019). Preventing Odors from Dry Sink Traps, Standard Operating Procedure EHS-017. CSU Pueblo Facilities Management. university procedure Localised sulfur-like odours frequently trace to a dry sink trap or unused floor drain; without water in a trap, sewer gas is drawn into the room; prevent by running or pouring water into drains at least once a week. (How traps lose their seal)
  11. Studor (2018). Studor Mini-Vent Air Admittance Valve: Product Information/Specification Sheet. Studor (IPS Corporation); copy at plumbingsupply.com. manufacturer data sheet Opens and admits air under the negative pressure of a discharging fixture; closes by gravity when flow stops; opening pressure −70 Pa; tight at 0 Pa or higher; air flow capacity 7.5 L/s (EN 12380). (How traps lose their seal)
  12. Agency for Toxic Substances and Disease Registry (2024). Hydrogen Sulfide ToxFAQs. U.S. Department of Health and Human Services (CDC/ATSDR). public health agency Rotten-egg smell noticeable at about 0.0005 ppm; often called sewer gas; smell lost after 2–15 min near 100 ppm, so odour is not a reliable warning; very high levels (> 500 ppm) can cause sudden unconsciousness or death; flammable. (How traps lose their seal)
  13. ILO and WHO (2018). International Chemical Safety Card 0291: Methane. International Labour Organization. international safety card Colourless, odourless gas; explosive limits 5–15 % by volume in air; can cause suffocation by lowering oxygen in confined areas. (How traps lose their seal)
  14. International Code Council, PMG Membership Council (2023). CodeNotes: Installation of Air Admittance Valves (based on the 2021 IPC and IRC). International Code Council. code body guidance An AAV lets air into the drainage system under negative pressure to prevent trap siphonage; closes and seals at zero or positive pressure; does not relieve positive pressure, so at least one vent must extend outdoors; ASSE 1051 (branch) and 1050 (stack) valves; must be accessible; manufacturer's instructions apply. (Trap seal calculator)

Simplifications