Plumbing Safety, Codes and Estimating
Core concepts
Safety covers the jobsite and the system: eye and hand protection when cutting and soldering, ventilation when using solvent cement and lead-free solder, fire watch and shielding when soldering near combustibles, safe handling of gas appliances, and confined-space entry rules for pits and vaults. Codes cover permits, inspections, pressure testing (typically hydrostatic at a specified pressure for a specified time), disinfection of potable lines, and protection of the potable supply from contamination.
Traps in questions
Expect questions that confuse the code edition adopted by the authority having jurisdiction with a national model code - the AHJ decides. Watch for items on testing: air testing is often restricted for plastic drainage, and hydrostatic testing is standard for supply. Estimating traps include forgetting fittings and waste allowance, mixing labor hours with material cost, and ignoring the difference between takeoff quantity and order quantity.
Worked example
Rule of thumb for estimating: material takeoff plus 5–10 percent waste for pipe and fittings, then labor hours by fixture or by linear foot, then add overhead and profit. For a 100-foot run of 1-inch copper with 20 fittings, order 110 feet of pipe and 22 fittings to cover cuts and defects, and price the solder and flux separately.