Drainage

Gravity needs slope

Drain pipe must fall continuously toward the tank. Road motion does not fix a belly full of standing water. Use adequate diameter for food particles and shower hair.

Traps

A P-trap blocks gas while it holds water but can evaporate, siphon or freeze. A listed waterless membrane trap saves height and resists dry-out but needs correct orientation and cleaning.

Tank inlets

Place inlets so splashing/foam do not block the vent or back up another fixture. Multiple inlets need enough headroom above the full level.

Service

Add removable strainers and cleanouts at likely blockage points. Secure drain lines for vibration and protect underslung sections from impact.

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.