EXPLAINER: How long does bottled water last before it becomes unsafe to drink?
As a "very strong" El Niño begins in the Philippines, some Filipinos are stocking up on drinking water as the climate phenomenon brings drought and less rain.
The worry about running out of water was made stronger after National Water Resources Board executive director Sevillo David Jr. said in an interview with dzMM that the NWRB lowered the water allocation from Angat Dam to Metro Manila in preparation for the effects of El Niño.
Then on Monday, Oct. 5, Science and Technology Secretary Renato Solidum Jr. confirmed that by the end of March 2027, all provinces in the Philippines are expected to be under a drought.
Despite calls from Malacañang and other government agencies not to hoard bottled water as the country currently has enough supply, numerous social media posts have circulated showing people stocking up on essentials, especially bottled drinking water.
It's important to keep in mind, however, that aside from straining general supplies and increasing the risk of price hikes, hoarding bottled water may also come with a health warning.
Is hoarding bottled water a good idea?
The Food and Drug Administration does not recommend hoarding bottled water because of the potential health risks it may bring.
"Water itself does not spoil, but plastic containers can degrade over time," FDA Officer-in-Charge Director General Atty. Franklin Anthony M. Tabaquin IV told PhilSTAR L!fe.
"While most manufacturers print a one- to two-year expiration date, extended storage may allow air to enter the PET bottle, or the PET bottle itself may degrade and affect the contents by altering its taste or, worse, the PET bottle itself may leach into the water," he continued.
A paper published on ScienceDirect in 2022 showed that PET bottles are semicrystalline thermoplastic polyester, a type of plastic polymer.
As the plastic breaks down over time, it can form microplastics or particles that are 5mm or smaller in length, per an article published by the National Institutes of Health in 2024. As they further degrade, the microplastics become nanoplastics, which will eventually seep into the water the PET bottle contains. Because they are tiny enough, these nanoplastics can then enter the body's cells and tissues once ingested.
This is why the FDA discourages keeping a large stock of bottled water.
"To put it simply, hoarding bottled water can lead to chemical leaching from plastics and degraded water quality," Tabaquin told L!fe.
Processing water
According to the NWRB's David, the main source of raw water in Metro Manila and the surrounding provinces is the Angat Dam. Water treatment plants are also now being run at Laguna Lake and Marikina River.
Raw or untreated water from natural sources, however, isn't safe to drink because of possible microbial contamination, per the World Health Organization.
Water in PET bottles undergoes several filtration processes before it becomes ready to drink. Running the water through numerous preparatory stages makes sure it is clean.
"In the first process, water passes through pre-filtration, multi-media filtration, micro-filtration, ultra-filtration, and nano-membrane filtration, followed by UV treatment for disinfection," Tabaquin explained.
The second process repeats pre-filtration and multi-media filtration but adds carbon filtration, softening, bag filtration, reverse osmosis, and again, UV treatment. Water is then purified, per the FDA officer.
After that, the water is transferred to a bottle-filling machine and undergoes visual inspection, coding, and labeling. Wrapping up the process, the bottles are then boxed or shrink-wrapped, then sent out for distribution.
Storing bottled water in good condition is key to having safe water to drink when you need it.
Tabaquin suggested storing bottled water in a cool, dry place away from direct sunlight. The Centers for Disease Control and Prevention also said that your storage area must be clear of toxic substances, such as gasoline, pesticides, or household cleaning agents.
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