Water Knowledge
What is Reverse Osmosis?
A clear introduction to RO membranes, operating pressure, contaminant reduction, wastewater and maintenance.
How it works
Reverse osmosis uses pressure to move water through a semi-permeable membrane. Water molecules pass through while many dissolved substances are retained and discharged in a concentrate stream.
What RO can reduce
Depending on membrane quality, pressure and system design, RO may reduce dissolved salts, nitrate, lead, arsenic, fluoride, some PFAS compounds and very small particles.
Important limitations
Performance is not identical across all products. Certification, laboratory method, feed-water composition and membrane condition must be considered before comparing removal percentages.
What to compare
| Membrane capacity | Usually expressed in GPD or liters per day |
| Recovery ratio | Filtered water compared with concentrate water |
| Operating pressure | Affects flow and rejection performance |
| Maintenance | Pre-filters protect the membrane and require replacement |