An A-Z guide for water-related terms.

Parts Per Million/Billion

The EPA uses parts per million (ppm) and parts per billion (ppb) to set standards.  They measure an amount of a single contaminant allowed in drinking water. Neither is a set unit of measurement, but rather an abstract reference to a percent of total mass. For example, four drops of ink in a 55 gallon bucket is equal to one part per million.

pH Level

pH or potential of hydrogen is a scale of acidity from 0-14. Neutral solutions, including water, are rated at 7. More acidic solutions have a lower pH level.

Point Of Use Filter

A point of use, or POU, filter purifies water at the point where water is actually used. Whether at your kitchen faucet, a refrigerator dispenser, or your shower head, a POU filter makes clean water happen.

Potable Water

Potable water is water that is ok to use for drinking and in your household. See Clean Water.

Powdered Activated Carbon

Powdered Activated Carbon is made from powder granules less than 1mm in size allowing for a large surface to volume ratio.

Pressure Test

Pressure is a key component of the Reverse Osmosis process, RO systems require a pressure test after installation. This test involves closing the RO faucet and allowing pressure to build for 2 hours, then checking for leaks.  Typically seen as part of an RO system installation process.

Private Water

Private Water is water which is privately supplied, usually via a well. This water is not transported by a Water Supplier or treated by the city. It is the responsibility of the well owner to ensure that the water is safe and healthy.


Purging a filtration system involves running water through the system after installation. It’s important to purge a system before using it. There will be some murky water that emerges. Run the water for a specified amount of time (it depends on the product) until the water is clean.