Water, on its own, should not go bad. However, microbes living in the water can cause it to go bad. Algae, mold, bacteria and other pathogens exist in water and can result in water that tastes bad and may be unhealthy. Chlorine that is added to our water supply is intended to eliminate these pathogens.
Filtering water is meant to remove dangerous pathogens as well as the chlorine from the water.
Question: But does this mean that filtered water is more likely to go bad than tap water?
Answer: Not necessarily. Filtered water can last much longer if stored under the right conditions and should last in excess of 6 months. The following factors are important to ensure that filtered water does not turn bad:
1. The Storage Container
It is essential to ensure that the storage container is sterile and that no pathogens can contaminate the filtered water supply. Storage in glass bottles is recommended. Plastic containers should be BPA free and designed specifically for the storage of water. Stainless steel is another hygienic storage option. Bottles or plastic containers should preferably be dark to prevent light from affecting the contents. Containers should be able to seal properly to prevent any pathogens or microbes from entering the water while being stored.
2. The Storage Location
Filtered water should be stored in a cool, dark place. The refrigerator is ideal although any cool place that is dark will also suffice. Remember to label the water containers and drink before it reaches its expected expiration date of about six months. This is especially important if you are planning on long-term water storage for emergencies.
3. Adding Chlorine
It is possible to add a small amount of chlorine to filtered water in order to make it last longer. However, this is not recommended unless the water is intended for long-term storage of over a month. Chlorine will break down after a period of time and become ineffective at eliminating or controlling pathogens that exist in the water. If water is being filtered with the express purpose of removing chlorine, adding it back into the water after filtering will negate this purpose.
Do NOT use stainless steel containers if the water does contain chlorine or if adding chlorine. The chlorine can cause the metal to corrode or break down and contaminate the water. Enamel coated stainless steel containers are better suited to use with water containing chlorine.
4. Accessing The Water
Once you have sealed the water container, it is not recommended to access it until it is consumed. Every time you open a bottle of water, it is exposed to pathogens that could contaminate the water. FEMA (Federal Emergency Management Agency) recommends discarding filtered or bottled water after a period of 2 weeks once the seal has been broken. As long as the seal remains in place, the water should be safe for consumption anywhere from 6 months to 2 years after bottling.
5. Room Temperature
It is mostly recommended to refrigerate your filtered water as the cooler temperature will make it last longer. However, if you are filtering water for daily use and not for long-term storage, it should be safe to keep the water at room temperature for about two weeks. If you are storing water for an extended period of time in the event of an emergency, the water should be rotated out every six months.
Although the general recommendation is to store water for no longer than 6 months, it can last much longer under the right conditions. Filtering the water, sterilizing the container and storing filtered water in a cool, dark place can increase the longevity of the water for one to two years.