POU Cooler Sanitation

New technology offers quick and easy cooler sanitation

Some bottled water cooler reservoirs may become vulnerable to contamination when the bottle is remove. The “No Spill” variants on these are an improvement, but the less-than-ideal conditions in the reservoir may be favorable for bacterial growth if not sanitized adequately. Frequent turnover of individual bottles helps limit the overall bacteria build-up, but low-use coolers can develop off-tastes.


In most cases the bacteria involved are harmless as they are the same ones we are exposed to every day—heterotrophs that are a subclass of mesophiles. Mesophiles are bacteria that grow best at moderate temperatures. Their optimum growth temperature is between 25° C and 45° C (77° F and 113° F). Most bacteria are mesophiles and include common soil bacteria and bacteria that live in and on the body. While most would not make people sick, they will make the water taste bad if allowed to grow long enough.

Point-of-Use (POU) coolers are a unique variant with special problems of their own. In most cases, POU coolers have larger overall reservoirs with only a small portion that is really cold. Because the object is to provide good tasting drinking water, the disinfectant (i.e. chlorine) is filtered out prior to the water entering the reservoir. This combination of mild temperature and no disinfectant yields an ideal growth situation for bacteria. Many manufacturers work hard to provide solutions to this microbial growth problem through various methods such as UV sterilization, intermittent ozone introduction, etc. with mixed results.
Why Cooler Sanitation?

So, how often should we sanitize our POU coolers? If you are providing POU (or bottled water) service in the European Union, you would be required by regulation to sanitize your coolers every three months—an expensive proposition. While we don’t have such regulation in the U.S. and Canada at present, there is a good possibility it may migrate here some day. Regular sanitation also may become a marketing tool prior to any formal regulation.

The International Bottled Water Association (IBWA) has published a recommended method for cooler sanitation. It features 12 steps and requires the use of household bleach. This could be a time-consuming and expensive procedure if undertaken by paid company personnel.

Most cooler sanitation in the U.S. and Canada takes place at the dealer’s location and requires transportation back and forth from the customer’s site.

In Europe, however, this sanitation most often occurs at the customer’s site and is performed by a team employed by the water service supplier.

Frequent cooler sanitation could be easier to accomplish if it is performed on-site, without chemicals and especially if the coolers were inherently inimical to microbial growth.

New Technology

A new POU cooler introduced by Amphion, San Antonio, Texas, addresses both of these issues among others. The POU cooler has a reservoir of nearly 5-gal. capacity and keeps the entire volume at a temperature of approximately 4° C. This greatly inhibits growth of mesophile types of bacteria. In addition, the reservoir has a disposable liner that makes the process very easy. The disposable liner along with reusable faucets is all that touches the drinking water so when this element of the cooler is removed and a new one installed, sanitation is assured. The process takes less than 10 minutes
including any necessary filter change.

A lot of new technology makes this work. First, the disposable liner is made from a medical-grade polyethylene that imparts no taste or odor to the water. Next, the .035-in.-thick liner sits on an aluminum cold plate that has more than 75 sq. in. of heat transfer surface. This combination increases effective heat transfer by an order of magnitude over conventional tube wound stainless reservoir combinations and results in fast cool-down with less compressor-run time.

Level control floats found in most POU coolers are in contact with the water that is most likely to grow bacteria (warm) and the floats are difficult to clean and sanitize. This cooler also utilizes a side benefit of the thin film liner. A two-position (high/low) membrane switch is inserted between the liner and the reservoir insulator wall where pressure of the water inside the liner operates the sensitive switches with no contact between the drinking water and switch. This results in approximately half-gal. refill increments that eliminate the possibility of TDS problems due to insufficient RO rinse time. Because the level detector is outside the liner, there is no risk of residual microbiological contamination.

An electronic micro-controller scans each of the cooler’s critical parameters several times per second. These include an overfill high level detector, disallowed level switch conditions (i.e. lower level switch showing no water while the upper switch shows water present), back-up battery energy level, regular level switch conditions for refill operations, and presence or absence of electrical power to the cooler. Any discrepancy in these areas (except power loss) causes the cooler to close both solenoid valves, turn off the compressor and sound an alarm. If the electrical power fails the controller shuts down the water solenoid valves, waits until power is restored and then restarts the compressor if five minutes have passed, thus preventing a “locked rotor” condition from momentary power interruptions.

Cooler sanitation would not be complete without considering gross rehabilitation. When a cooler becomes dirty enough to require disassembly and thorough cleaning a dealer or end-user is faced with an entirely different set of problems. First, most coolers use a coffee-cup-type of cold reservoir insulation (polystyrene). This exposed insulation attracts a number of insects and rodents that find it to be an ideal nesting material, and its replacement is usually difficult and expensive. Even if it is not structurally damaged, the material discolors and cannot be pressure washed without damage. In addition most coolers utilize thermostats and other electrically “open” components that make pressure washing a questionable cleaning technique. Amphion’s all-plastic construction (except for basic refrigeration components) and the absence of a thermostat allow pressure washing. There is no exposed foam insulation and all other power-level components are sealed. The three-panel skin allows individual panel replacement in the event one is damaged.

Final Words

Cooler sanitation is an opportunity to turn a problem into a new value added service that can add significantly to cash flow. By offering customers a program that includes regular cooler sanitizing in addition to the normal filter change interval, water service providers can enhance their company’s image as well as the quality of their drinking water product.


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About the author

John Cooke, BSChE, PE is president of Amphion Water Coolers, San Antonio, Texas. He can be reached at 210.349.1211, or by e-mail at cooke@amphioncoolers.com.