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Reverse Osmosis (RO) Systems and Chromium-6
As part of the city’s ongoing commitment to safe and reliable drinking water and in response to both community interest and the city’s ongoing evaluation of water treatment options, we want to share information about reverse osmosis (RO) systems. This includes how they work, what they can do for your home and how they relate to the city’s current efforts to address Chromium-6 at the source.
What Is Reverse Osmosis?
Reverse osmosis is a water treatment process that uses a special membrane to remove impurities, including salts, metals, chemicals and some microorganisms. RO systems are effective at improving water quality and taste and they are capable of removing Chromium-6 from drinking water. There are two main types of RO systems commonly used in homes:
- Whole-Home RO Systems- A whole-home RO system purifies all water entering a home, from faucets and showers to appliances and outdoor lines, by passing it through filters and a membrane that removes contaminants. The clean water is distributed throughout the plumbing, while wastewater is drained away. These systems provide purified water throughout the home, protect appliances from scale and mineral buildup and are especially useful for homes with private wells or poor water quality. However, they are expensive to install and maintain (typically $5,000–$15,000), can waste two to three gallons of water for every gallon purified, remove beneficial minerals and require significant space for installation. Whole-home RO systems are ideal for properties with private wells that may experience significant water quality issues.
- Under-the-Sink RO Systems- An under-the-sink RO system purifies water at a single faucet, typically in the kitchen, by passing tap water through filters and a membrane inside a compact unit beneath the sink. Clean water is delivered through a dedicated drinking-water faucet, while wastewater is drained through the sink line. These systems provide high-quality water for drinking and cooking, are smaller, more affordable (usually $200–$600) and easy to install and maintain. However, they treat only one faucet, have slower water flow with limited storage and generate some wastewater. Under-the-sink RO systems are best for residents seeking purified water primarily for drinking and cooking.
City Efforts and Home RO Systems
The City recently completed a feasibility study (still in draft form) to explore treatment options for removing chromium-6 from the municipal water supply. RO was identified as one effective method and is currently under evaluation; however, so far it is the most expensive option considered. While home RO systems can provide short-term reassurance and improve drinking water quality, they are not a permanent solution. Addressing chromium-6 at the source through City-managed water treatment remains the most reliable and equitable way to ensure safe drinking water for all residents.
The City also wants to reassure residents that there are no restrictions in the municipal code on installing RO systems in their homes. If using one of these systems provides peace of mind, residents are welcome to do so. Residents should also be aware that these systems can increase water and wastewater use, which will affect their water bill and the City’s efforts to reduce overall water consumption and manage wastewater loading at our Water Quality Control Facility. Ultimately, long-term water safety depends on the City’s continued efforts to address chromium-6 at the source.