Point of use, usually shortened to POU, means treating water at the place it is used rather than where it enters the building. In a household that nearly always means the kitchen tap, and the practical question is which of five formats fits your kitchen, since they differ more in installation than in what they can achieve.
Why point of use rather than point of entry
Because the water that matters most is the small volume people drink and cook with, and treating only that is far cheaper than treating everything. Fine filtration and membranes both restrict flow, which is tolerable at one tap and expensive across a whole house. Ingestion is also the exposure route for most contaminants that concern people. So the sensible arrangement in many houses is coarse treatment at the point of entry and thorough treatment at one tap.
The five formats
A pitcher, which needs nothing at all and has the smallest capacity. A tap mounted filter, which replaces the aerator and needs a standard thread. A countertop unit fed by a diverter, which holds more media and comes off when you move. An under sink cartridge plumbed into the cold feed, invisible and longer lasting. And an under sink system feeding a dedicated tap, which is required for reverse osmosis and treats only what you actually drink.
What separates them in practice
Capacity and therefore running cost per volume, which improves as the format gets larger and more permanent. Flow, which is poor on a pitcher and a tap mount and good on an under sink system. Whether it survives a house move, which favours the removable formats. And whether it fits at all, since the tap mounted and countertop formats both need a standard aerator thread that many designer and pull out taps do not have. Check that before anything else.
Matching the format to the finding
For chlorine taste, any of the five with a decent carbon cartridge will do, so choose on convenience. For a certified reduction of a specific contaminant, choose a model whose certification names it and check the certifier's own listing rather than the packaging. For nitrate, fluoride or dissolved salts, only a membrane system will do, which means the under sink format with a dedicated tap. Our whole house filter guide covers the point of entry stage that complements it.
Questions people ask about pou water filter
What does point of use mean?
Treating water where it is drawn, typically at the kitchen tap, rather than where it enters the building.
Why not treat the whole house instead?
Fine filtration and membranes restrict flow and cost far more at household scale, and ingestion is the exposure route that matters most.
Which format is cheapest to run?
An under sink system with a dedicated tap, because only water you actually drink passes the cartridge. Pitchers cost most per volume.
Which handles nitrate or dissolved salts?
Only a membrane system, which means an under sink reverse osmosis unit with its own tap.