Costs of R.O. (reverse osmosis) Water for your Home

Reverse osmosis (R.O.) can reduce contaminants in drinking water, typically dissolved solids and suspended matter - nitrate, sulfate and sodium among them. Coupled with carbon filters, reverse osmosis systems can also reduce soluble organic compounds (SOCs) and VOCs (volatile organic compounds). This technique is gaining popularity but what are the costs and considerations?

One of the best places to start is to have your water tested. If your water comes from a municipal supply it is tested regularly by the water authority. Information about these tests can be obtained from your local water company. If your home is on a private well you can call the County Health Department or State Environmental Protection Agency to find out about groundwater quality and possible contaminants in your area.

The EPA sets maximum limits on about 90 contaminants that are commonly found in drinking water. Local health departments and private labs offer varying degrees of tests. A basic test for coliform bacteria will run about $50. A more comprehensive test package like those used in new homes can run $2-300 but can include testing for lead, arsenic, volatile organic compounds (VOCs) and a wide range of other possible contaminants.

Knowing what’s in your water will help you determine the best water purification strategy. For instance, reverse osmosis are not effective in treating water with coliform bacteria, a common contaminant.

Reverse osmosis filters water through a membrane with microscopic openings. Water molecules can pass through but larger compounds are stopped. Some units have a pre-filter that sorts out suspended particles and protects the membrane. The type of R.O. membrane you choose depends on the contaminants present in your water as well as the water supply rate and pressure.

Because R.O. “sorts” molecules, the volume and rate of treated water is lower than the untreated supply. Treated water can be stored in a pressurized tank to be available on demand. Storage tanks are typically 2 to 5 gallons and can be located under sink or elsewhere in the home. Some R.O systems have a carbon filter that is either used before the membrane or as a post filter. From there, water is available from both a “treated” tap and an “untreated” tap.

R.O. systems can filter out up to 95% of the water that passes through. The rest is discharged as waste water. This aspect has several considerations. The units use a lot of water and they can strain septic systems.

R.O. systems range in price from under $500 up to $3,000. They have operating costs for electricity (to pump the water) and for replacement parts. Replacement membranes can cost up to $200 and filters run about $50. Household units are designed to deliver between 2 to 10 gallons of treated water per day with rejected waste water equivalent of up to 20 times the volume of water treated. They can be effective in removing contaminants but homeowners should research this water-purification technique thoroughly before making an investment.