Plumbing materials

PEX

PEX-A and PEX-B describe manufacturing methods, not universal fitting interchangeability. Expansion, crimp and clamp systems require their approved pipe, rings, fittings, tools and inspection rules. Follow one documented system.

Flexible hose

Potable reinforced hose is useful at pumps, heaters and moving/service points. Confirm pressure, temperature, bend radius and drinking-water rating. Soft vinyl can kink, taste, harden or be unsuitable for hot/pressurized use.

Rigid plastics

PVC/CPVC may be acceptable only within their ratings and applicable rules, but rigid joints tolerate vehicle vibration and freezing poorly. Never use drain-only pipe for pressurized potable service.

Threads and seals

NPT is tapered; NPSM and hose threads are different. Use the fitting maker's approved PTFE tape or sealant, keep sealant out of the water path and do not over-tighten plastic. A threaded joint does not become safer by forcing another turn.

Build rule

If you cannot reach it, isolate it, drain it and explain its pressure/temperature or water-quality job, it is not ready to hide behind a wall.

CHAPTER CHECK

• I can explain the purpose and failure mode of each item in this chapter. • I know which manufacturer limit or water-quality claim controls my choice. • I added the valve, access, drain, measurement or maintenance task to my drawing/checklist.