Supply Piping & Pressure
~12 min read · Identify copper, PEX, CPVC, polybutylene and galvanized supply — and each material’s risk.
Supply piping is identified before it is judged: copper, PEX, CPVC, galvanized, and the recall-era polybutylene each carry a known service story. Add functional flow testing and visible-leak hunting, and the supply inspection writes itself.
Material identification and stories
Copper: decades of service; findings are green corrosion at joints (flux or leaks), pinhole leaks in aggressive water, and pre-1986 lead solder (note for testing). PEX: flexible, color-coded; keep it off UV and check fitting systems (early brass fittings in some systems dezincified). CPVC: cream-colored, rated for hot water; brittle with age — cracks at fittings. Galvanized steel (pre-1960s): corrodes SHUT from inside — rust flakes choke flow, and rusty water plus weak upper-floor pressure is its signature; leaks start at threads. Polybutylene (gray, ~1978–1995): class-action-era material whose acetal fittings and pipe degrade with chlorine — sudden failures; report by name with insurance/replacement implications.
- Copper: joints, pinholes, pre-'86 lead solder
- Galvanized: internal choking — flow findings + thread leaks
- Polybutylene (gray): name it, degradation mechanism, replacement conversations
- PEX/CPVC: fittings, UV, brittleness
Functional testing
The inspector's flow test is practical: run the highest-and-farthest fixtures simultaneously (functional flow — does the shower die when the toilet flushes?), watch for hammering (water hammer — loose pipes or absent arrestors banging on valve closure), and note static pressure where a gauge is used: the working band ~40–80 psi; over 80 psi calls for a pressure-reducing valve (fixture and heater stress). The main shutoff valve is located and reported (operating it is discretionary — old gate valves seize and drip when exercised).
- Simultaneous-fixture flow test finds choked systems
- Hammer = restraint/arrestor finding
- ~40–80 psi working band; >80 needs a PRV
- Locate the main shutoff; note condition
Leak evidence and connections
Visible-system hunting: green/white crust on copper, rust weeps at galvanized threads, mineral tracks below fittings, active drips, corrosion at dielectric transitions (copper-to-galvanized junctions corrode galvanically without proper unions), saturated cabinet floors under sinks, and supply lines to fixtures (braided vs aged rubber washing-machine hoses — a flood-risk note). Wells and pressure tanks get their own functional notes where present.
Worked example
A 1948 house updated in stages: basement shows galvanized mains transitioning to copper with a direct threaded joint crusted in white-green corrosion; the upstairs shower drops to a trickle when the kitchen faucet runs; static pressure reads 95 psi; and a coil of gray plastic pipe feeds the laundry. Assemble the supply report.
Layered eras, layered findings. The trickle-under-load is galvanized doing what galvanized does — internal rust choking flow; the material is at end of life: budget re-piping (the finding is the flow test plus the material's story, not a guess). The crusted junction: copper meets galvanized without a dielectric union — galvanic corrosion actively eating the joint; correct the connection. 95 psi: above the ~80 threshold — a PRV is needed; high pressure also accelerates every weak point just described. The gray coil: polybutylene by color and era — name it, explain chlorine-degradation failures, and raise the insurability/replacement conversation. One system, four eras, each judged by its own account.
Common exam pitfalls
Judging galvanized by its exterior.
It fails from the inside — the flow test under simultaneous demand is the diagnostic, not the paint.
Missing polybutylene because it's 'just gray plastic.'
Gray + 1978–95 era = report by name with its failure history — buyers and insurers treat it specifically.
Ignoring pressure above 80 psi.
High static pressure stresses heaters, valves, and hoses — PRV recommendation is the standard call.
Name the metal, run two taps, read the crust, mind the pressure — every pipe tells its era's story.
Recap
- Identify materials; each carries a known failure story
- Galvanized: internal choking → flow findings
- Polybutylene: gray, era-bound, report by name
- Functional flow test under simultaneous demand
- 40–80 psi band; >80 → PRV
- Dielectric transitions, visible leaks, hose conditions
Prove it: 10 questions on this topic
Every lesson ends with a ten-question check in the free course — your progress syncs between the web and the EstatePass app.
Studying for the National Home Inspector Examination? Track every lesson free — progress syncs with the app.
Start freeMore in Plumbing
Study smarter in the free dashboard
- Every lesson tracked, synced with the iOS app
- Ten-question checks after each lesson
- Lesson videos, flashcards and mock exams
No credit card required.