Drinking Water Treatment Diagram – Steps of the Process

All 12 parts on the diagram

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Start here: the 5 steps 5

Coagulation A chemical is mixed in fast. It makes tiny particles stick together.
Flocculation Gentle stirring makes the small clumps collide and grow.
Sedimentation Still water lets the floc settle to the bottom.
Filtration (filter) The water runs down through a filter that traps the remaining particles.
Disinfection A disinfectant such as chlorine is added. It kills germs left in the water.

Mix and settle 4

Source water Water from a lake, river or reservoir, before it is treated.
Coagulant A chemical with a positive charge, such as aluminum sulfate.
Floc Clumps of particles that have joined. They are heavy enough to sink.
Sludge The settled floc on the floor of the basin. It is removed.

Filter to tap 3

Filter media Layers that fill the filter, such as anthracite coal and sand.
Storage tank Treated water is held here before it goes out to the pipes.
Distribution pipes Pipes that carry the treated water to homes and businesses.

How this list was compiled: Read 2026-10-03; a name is kept only where two of these use it. (1) Wikipedia, Water purification, text only (the raw (source) water, from rivers, lakes and reservoirs; coagulant chemicals such as aluminum sulfate added in a rapid mix; flocculation basins where gentle mixing helps floc form; the sedimentation basin, or clarifier or settling basin, where floc settles and sludge collects on the bottom; filtration through sand, often with a layer of anthracite coal or activated carbon above it, the filter media; disinfection, most often with chlorine; temporary storage in a contact tank or clear well; storage and distribution systems). (2) A US public water utility's page on its treatment process (coagulation with a positively charged coagulant like aluminum sulfate; flocculation, gently stirring so floc particles join and grow; sedimentation, where the floc falls to the bottom of a tank and the sludge is removed; filtration through layers of anthracite coal and of sand, known as filter media; disinfection with disinfectants such as chlorine, with baffles for contact time; water moving through pipes in the city). (3) Safe Drinking Water Foundation, Conventional Water Treatment: Coagulation and Filtration (coagulation, sedimentation, filtration and disinfection as the conventional method; coagulants with a positive charge; floc that settles; a settling tank or clarifier; filters of sand, gravel and charcoal). (4) US Environmental Protection Agency: Drinking Water Distribution Systems (pipes and storage facilities; mains that carry water from the treatment plant to the consumer); Basic Information about Source Water Protection (source water is the rivers, streams, lakes, reservoirs, springs and groundwater that supply drinking water); the issue paper Finished Water Storage Facilities, 2002 (ground storage tanks or reservoirs hold finished water; a clearwell is counted as part of treatment, not as storage). (5) An operator training manual written for the same agency, Water Treatment Plant Operation, volume 2, 1988 (source water and raw water; settling basins and sedimentation basins, with sludge removed from the bottom; the clear well after filtration). The utility's page does not use 'source water' and names no storage tank, so those two names stand on Wikipedia and the agency's pages. Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. A schematic, not to scale. Licence: own work

How it works

A drinking water treatment diagram that follows the water from its source to a home: coagulation, flocculation, sedimentation, filtration and disinfection, then the storage tank and the pipes.

Read the full guide

Mix and settle

A coagulant is stirred quickly into the source water: that is coagulation. Slow stirring then lets the small clumps grow into floc, which is flocculation. In the sedimentation basin the floc sinks and collects on the floor as sludge.

Filter to tap

The clearer water runs down through the filter media, layers such as anthracite coal and sand. A disinfectant such as chlorine is added. The treated water waits in a storage tank and leaves through the distribution pipes.

Not every plant uses every step, and some add others. These are the names of the common, conventional process.

Questions and answers

What are the steps of water treatment in order?

Coagulation, flocculation, sedimentation, filtration and disinfection. The treated water is then stored and sent through pipes to homes and businesses.

What is the difference between coagulation and flocculation?

Coagulation is the fast mixing of a chemical that makes tiny particles stick together. Flocculation is the slow, gentle stirring that follows, so that the small clumps collide and grow into floc.

What is floc in water treatment?

Clumps of particles that form after a coagulant is added. Floc is heavy enough to settle to the bottom of the sedimentation basin, where it collects as sludge and is removed.

Can I practice here for “label the following diagram that illustrates the typical process for water treatment”?

Yes, for practice. That sentence is the instruction of a labeling exercise. The drawing here is our own and not a copy of any course figure, so your figure may show other tanks or use other names.