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Reverse Osmosis Explained: How RO Systems Work

Understanding the science behind reverse osmosis filtration and what contaminants it removes from your drinking water.

Published: 1/16/2025

Summary: Reverse osmosis uses pressure to force water through a semi-permeable membrane, removing up to 99% of contaminants for pure drinking water.

What is Reverse Osmosis?

Reverse osmosis (RO) is a water purification process that uses a semi-permeable membrane to remove ions, molecules, and larger particles from drinking water. It's one of the most effective methods for producing clean, pure water.

How RO Systems Work

  1. Pre-filtration: Water passes through sediment and carbon filters
  2. RO Membrane: High pressure forces water through the membrane
  3. Post-filtration: Final carbon filter removes any remaining taste/odor
  4. Storage: Clean water is stored in a pressurized tank

What RO Removes

Contaminants Removed (99%+)

  • Lead, mercury, arsenic
  • Chlorine and chloramines
  • Pesticides and herbicides
  • Pharmaceuticals
  • Bacteria and viruses
  • Dissolved solids (TDS)

What Stays Behind

  • Minerals like calcium and magnesium
  • Some beneficial trace minerals

System Components

Pre-filters

  • Sediment filter: Removes dirt, rust, sand
  • Carbon filter: Removes chlorine, taste, odor

RO Membrane

  • Semi-permeable: Allows water molecules through
  • High pressure: Forces water through tiny pores
  • Contaminant rejection: Blocks larger molecules

Post-filter

  • Carbon polishing: Final taste improvement
  • Storage tank: Holds purified water

Installation Considerations

Under-sink Systems

  • Most common for residential use
  • Requires dedicated faucet
  • Easy maintenance access

Whole-house Systems

  • Larger capacity
  • More complex installation
  • Higher initial cost

Maintenance Requirements

Filter Replacement Schedule

  • Pre-filters: Every 6-12 months
  • RO membrane: Every 2-3 years
  • Post-filter: Every 12 months

System Monitoring

  • Regular TDS testing
  • Pressure gauge checks
  • Flow rate monitoring

Water Quality Benefits

  • Taste: Clean, pure drinking water
  • Health: Removes harmful contaminants
  • Convenience: Always available at your tap
  • Cost: Cheaper than bottled water

Environmental Impact

  • Reduces plastic bottle waste
  • Lower carbon footprint
  • Sustainable water source
  • No transportation emissions

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