Water purification and safety

Microbes are invisible. Boiling or correct chemical disinfection can kill/inactivate most pathogens but does not remove salts, heavy metals or most chemicals. Filters remove only what their design and certification claim.

Multi-barrier thinking

Know the source -> settle/prefilter turbidity -> apply appropriate filtration -> disinfect -> store safely. UV needs clear water, correct flow, lamp intensity and power; shadowing/turbidity can defeat it. Carbon before UV may improve clarity but can remove chlorine residual.

Emergency treatment

CDC recommends a rolling boil for at least 1 minute, or 3 minutes above 5,000 ft/1,000 m. If boiling is impossible, follow current CDC/EPA directions for the exact bleach concentration and water condition. Do not improvise doses from memory.

Stagnation and biofilm

Warm, stagnant water and dead legs support growth. Keep the system clean, opaque and cool where possible; maintain disinfectant strategy; flush after storage; and sanitize based on the tank/component manufacturer and water history.

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.