Drain Dictionary

Water Flow & Hydraulics

Backflow, surcharge, water hammer and how water actually behaves in pipes.

Air Lock A pocket of trapped air in a pipe that blocks or restricts flow — common in hot water lines after work on the system, and in poorly vented drainage. Backflow Water flowing backwards through a system — sewage backing up a drain, or contaminated water reversing into the drinking supply — prevented by valves and air gap Self-Cleansing Flow The design principle that wastewater must move fast enough to carry solids with it — achieved through minimum gradients — so drains clean themselves in normal u Surcharge When a drain or sewer runs completely full and under pressure — flow beyond its gravity capacity — forcing water up and out of gullies, manholes and low fixture Water Hammer The bang or shudder in water pipes when flow stops suddenly — a pressure shockwave from fast-closing taps and valves, stressful to pipes and joints over time.

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Pipes & Materials (4) Drainage Structures (8) Blockages & Causes (14) Inspection & Technology (9) Repair Methods (6) Cleaning & Clearing (3) Plumbing Fixtures (3) Sewer Systems (8) Stormwater (8) Trade Terminology (5) Regulations & Standards (5) Tree Roots & Vegetation (2) Maintenance & Prevention (1)

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