General Plumbing Knowledge and Safety
Scope
Domain 1 covers the fundamentals every other domain assumes: how water comes in and waste goes out, which pipe materials are approved for which service, how joints are made, how systems are tested, and how to work without injuring yourself or the occupant.
Materials and joining. Know which materials are approved for potable water (copper, PEX, CPVC, galvanized steel) versus drainage (PVC, ABS, cast iron, galvanized). Solvent cement is for PVC, CPVC, and ABS only. Copper is soldered with lead-free solder and approved flux, or joined with press fittings. PEX uses crimp, clamp, or expansion fittings and must be protected from UV and physical damage. Threaded joints use tape or dope approved for the service.
Math you will actually use. One psi is about 2.31 ft of water column, and one foot of water column is 0.433 psi. Gallons in a pipe are about 0.0408 x (diameter in inches) squared x length in feet. One cubic foot holds 7.48 gallons.
Safety. Excavations 5 ft deep or more need a protective system and a competent person on site; spoils stay at least 2 ft back from the edge. Sewer manholes and deep vaults are confined spaces, so test the air before entry. Use lockout on feeders, protect against lead (pre-1986 solder, lead service lines), ventilate soldering fumes, and wear eye protection when cutting cast iron.
Traps. Unit conversions (head to psi) and "what is the first thing you do when conditions are unsafe" items. The correct answer to an unsafe condition is stop work, make the area safe, and notify the responsible party, never "work around it."
Rule of thumb. A 40-ft rise costs about 17 psi of static pressure (40 divided by 2.31).