Reverse Osmosis (RO) Water at Willy Street Co-op
About Our Reverse Osmosis Water Systems
The reverse osmosis (RO) water systems used at all Willy Street Co-op locations are provided and serviced by Total Water Treatment Systems, a Madison-based distributor and service provider for Culligan water treatment equipment.
Our RO systems process municipal water through multiple stages of filtration and purification. According to Total Water, these systems meet the NSF P473 and NSF/ANSI 58 drinking water standards for the reduction of polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), through reverse osmosis and point-of-use treatment technologies.
Total Water also reports that these industrial RO systems remove up to 99% of total dissolved solids (TDS) from municipal supply water. Reverse osmosis water typically exits the filtration system with a pH of approximately 5.0–6.5 and generally stabilizes to between 6.5–7.5 as it moves through the dispensing system.
How Our RO Water Is Filtered
Municipal water supplied to our stores passes through the following treatment stages:
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Water softening
Calcium and magnesium are removed from the municipal water supply. -
Carbon pre-filtration
Two stages of carbon filtration remove contaminants and particles that may remain after water softening. -
5-micron sediment filtration
A spun polypropylene filter removes very fine particles, including sand, rust, salt, and mineral scale. -
Reverse osmosis membrane filtration
A semi-permeable membrane removes up to 99% of total dissolved solids and other contaminants. -
Ultraviolet sterilization and final carbon filtration
The water is exposed to UV sterilization and passes through an additional carbon filter to improve taste and remove odors, discoloration, and residual chlorine. -
Continuous circulation system
The purified “product water” is circulated through a constantly moving, closed-loop distribution system designed to minimize the possibility of algae or bacterial growth. -
Final ultraviolet sterilization
A second UV sterilization step occurs immediately before the water is dispensed.
RO System Maintenance
Our RO systems receive regular preventative maintenance and testing through Total Water Treatment Systems, including:
- Monthly service inspections
- Monthly replacement of 5-micron sediment filters
- Monthly coliform bacteria testing
- Quarterly replacement of carbon pre-filter cartridges
- Annual sterilization of the entire system
- Monthly inspection of ultraviolet sterilization lamps, with replacement as needed
About Algae, Bacteria, and Mold Growth in Refillable Water Bottles
Algae growth in refillable water containers is a common occurrence when bottles are not properly cleaned and sanitized. Algae spores are naturally present in the environment and require three conditions to grow:
- Water
- Light
- Nutrients
Nitrogen and phosphorus, which can be present in some municipal water supplies, can provide nutrients that support algae growth. Infrequent cleaning, inadequate sanitization, insufficient sanitizer concentration, or exposure to direct sunlight can allow algae, bacteria, or mold to develop inside refillable containers.
A simple rinse or “swish and rinse” cleaning method using tap water or RO water is generally not sufficient to properly sanitize a refillable water container.
Recommended Bottle Sanitization Procedure
Based on guidance from Total Water Treatment Systems:
-
Prepare a sanitizing solution using:
- 2 tablespoons of household bleach per 5 gallons of warm water, or
- Approximately 1¼ teaspoons per gallon
*The bleach should contain 5.25%–6.15% sodium hypochlorite.
- Fill the container completely with the sanitizing solution to ensure all interior surfaces are contacted.
- Allow the solution to remain in the container for 2–4 hours.
- Empty the container, rinse thoroughly with warm water two or three times, and allow it to dry completely before refilling.
Why Is the Water Sometimes Warm?
Occasionally, RO water may dispense slightly warmer than expected if the dispenser has not been used recently or if the dispenser’s automatic purge cycle has not yet been triggered.
This occurs because water remaining in the internal lines of the dispensing system can gradually warm between uses. Once the dispenser runs long enough for fresh water from the continuously circulating system to reach the outlet, the temperature will return to normal.
