Reverse Osmosis at Home: How It Works and What to Check Before Choosing a System

You want to take water treatment at home a step further. As you compare equipment, you come across terms such as membrane, pressure, daily production, and remineralization.

Reverse osmosis may sound complicated, but understanding the basics helps you ask better questions before buying.

A membrane that separates two water streams

Reverse osmosis uses pressure to push water through a semipermeable membrane.

The process produces two streams: treated water and reject water, which carries the substances separated by the system. Along with asking how much a unit filters, ask how much water it uses to produce each liter available to drink. Source: EPA

The membrane usually works alongside other stages. The configuration depends on the model and the characteristics of the incoming water.

Which substances can it reduce?

Reverse osmosis systems can reduce various dissolved substances. Performance must be verified for each unit, however.

NSF/ANSI 58 includes tests for total dissolved solids reduction and specific additional claims, such as reduction of lead, nitrate, fluoride, or certain forms of arsenic. Certification under that standard does not mean a model includes every possible reduction claim. Source: NSF

Look for the contaminant you are interested in within the model’s documentation.

What this means in your kitchen

Imagine using the system to fill water bottles, make coffee, and cook. You need to know how much it can produce and how it delivers that water.

Before choosing, ask:

• How much treated water will be available at any given time.
• How long it takes to produce more.
• Whether it uses a tank or direct flow.
• What pressure it requires and whether it needs electricity.
• How much space the equipment and connections require.

Advertised output is measured under particular conditions. Ask what you can expect in your installation.

Efficiency is also part of the choice

Two units may produce treated water while using different amounts of incoming water.

Ask for an easy-to-understand ratio: liters of reject water for each liter of treated water, with the test conditions stated.

WaterSense, the EPA program, includes efficiency and performance criteria for point-of-use reverse osmosis systems. If a product claims that label, verify that it applies to the specific model. Source: EPA

Maintenance should be clear from the start

Request the replacement schedule for prefilters, the membrane, and any downstream cartridges. Do not assume every part lasts the same amount of time.

Also ask about cleaning, replacement parts, service, and procedures after a long period without use.

A useful comparison includes both the equipment cost and the cost of keeping it operating within its design conditions.

Choose based on your water

Reverse osmosis is a treatment tool. Its usefulness depends on the need you want to address.

At PFC, we want to help you understand each stage, its role, and the care it needs. Before choosing, tell us where your water comes from, what you want to improve, and how many people would use the system.

Free your water with PFC.

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