(See Owner's Manual for recommended cleaning frequency.)
Activate water shutoff and unplug the unit from power source.
Use rubber gloves to prevent scald when draining hot water.
Wipe down the cooler with a bleach solution (a tablespoon of bleach per gallon of water). Commercial water cooler cleaning agents such as Cooler Clean or H2OK can also be used.
Wipe the lid of the cooler and remove both the lid and reservoir cover.
Drain any remaining water in the reservoir through the faucets.
Wipe out the inside of the reservoir to eliminate any film.
Pour the cleaning agent into the reservoir and fill with water.
Allow 15 minutes and then drain the reservoir using each faucet. Repeat if necessary.
Replace reservoir cover and lid.
Allow the reservoir to refill.
Drain a few cups of water from each faucet and discard. Your cooler and reservoir are now cleaned and sanitized.
(Note: While the above procedures are generally effective and safe for cleaning bottleless water systems, it's imperative that you consult your Owner's Manual to ensure that you adjust or augment these general procedures as appropriate for your specific brand of cooler.)