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Yakima County's Nitrate
Treatment Pilot Program

Providing water treatment systems, education and technical assistance to households with individuals at high public health risk from nitrate contaminated wells.

Fact sheet on Reverse Osmosis (RO) – Treatment Considerations, (limitations, costs, operation and maintenance)

<< FAQ's Table of Contents

What are the limitations of a reverse osmosis (RO) treatment system?

Reverse osmosis treatment systems are affected by the quality of the raw water entering the system.  Hardness, iron level, total dissolved solids, pH, temperature and pressure all affect how well a system will perform and the cost of maintaining a system. 

RO treatment systems are not appropriate for treating water contaminated by coliform bacteria.  If bacteria are found in the water, then the contractor will install an ultraviolet light ahead of the treatment system to inactivate the bacteria.

What are the maintenance requirements of an RO treatment system?

Filters must be changed on a regular basis.  The time between changes will vary depending on the volume of water used and the quality of the incoming water.  On average, filters will need to be changed once a year and the membrane should be replaced every 2 to 4 years.

Water tests are also recommended to ensure the system is functioning properly.  The system installer will check the system once a year at no charge to see if it is functioning properly.  You may also periodically test for nitrate by purchasing and using nitrate test strips similar to what was included in a letter from Yakima County.

What are the costs?

Costs include initial installation costs, operating costs and maintenance costs. 

Homes selected for financial assistance will have systems installed at no cost.  Homes not selected will be eligible to have systems installed at a reduced cost.  The reduced cost is estimated between $695 and $990, depending on the type of system you need.

Electricity to pump the water and in some cases to operate an ultraviolet light are the only operating costs.  Because RO treatment systems waste approximately two gallons for every gallon produced, your well pump will need to operate slightly longer.

The system will require periodic maintenance to be effective.  A maintenance program being offered by the system installer will cost $18.95 per month for a typical system.  Alternatively, the homeowner can purchase the filters and membrane and perform the basic maintenance themselves for approximately $60 per year.  Installations with hard water, high iron or total dissolved solids levels may require more frequent filter changes resulting in higher maintenance costs.

Maintenance costs for a treatment system are generally significantly less than the cost of bottled water.  As a comparison, a gallon of bottled water costs approximately $1 and typical maintenance costs are approximately $1 for 10 gallons of water treated.