Reverse osmosis (RO) water system

Reverse osmosis (RO) systems force water through a semi-permeable membrane that excludes dissolved solids, heavy metals, fluoride, chlorine, sodium, nitrates, and most other contaminants. The result is water with 95-99% of dissolved solids removed.

Residential RO systems are typically point-of-use (installed under the kitchen sink) rather than whole-house. The water output rate is slow (1-2 gallons per hour from a typical residential RO), so systems include a holding tank that fills over time. Cost: $300-$800 for the system, $400-$1,200 with installation. Annual maintenance: filter replacements ($75-$200/year) and membrane replacement every 2-3 years ($75-$200).

The trade-offs: RO produces 1-3 gallons of waste water for every gallon of purified water (the brine that carries away the contaminants), making it less suited for whole-house use. RO removes beneficial minerals along with contaminants — some systems include mineral re-injection stages for taste. RO water is mildly aggressive on metal pipes long-term (typically not an issue at point-of-use scale).

For water treatment operators, RO is high-margin install work paired well with water softeners. Common selling pattern: 'whole-house softener for appliances + clothing + scale prevention; under-sink RO for drinking and cooking.' Recurring filter-replacement service builds long-term customer relationships.