As precious as it is, clean drinking water gets taken for granted until a natural disaster limits access.

Emergency response experts routinely advise homeowners to keep an emergency water supply safely stashed away — about a gallon of water per day per person, according to John Cummings, public information officer for the Honolulu Department of Emergency Management.

But if you didn’t have a supply, and a hurricane wipes out water sources, you should be familiar with ways to purify contaminated water, said Cummings, who will demonstrate purification techniques Saturday during an event called Ready2React Emergency Preparedness in the Toys R Us parking lot at Pearlridge Center.

The simplest way to purify water, once you’ve determined that it’s from a clean source or has been put through a sediment filter, is to use the power of the sun. Place your bottles of water on an aluminum pan and in full sun for a minimum of six hours. If it’s cloudy with little or no rain in the forecast, your water will need at least two days of exposure.

“It will not work on very rainy days,” Cummings said said.

Bottles used for solar disinfection should hold no more than 2 liters and made from the clearest, noncolored plastic available to allow for maximum heat build-up as well as exposure to ultra-violet light. Glass bottles are not as efficient, Cummings said. A key point to remember: The water must also be as clear as possible, because murky water will not allow maximum exposure to heat and light.

Dirty or questionable water should be run through a sediment filter, which is also referred to as a bio-filter. Cummings used an upside-down 1.5-liter plastic bottle to create his filter. He began by cutting off the bottom of the bottle and putting in a piece of terry cloth, torn from an old towel, to clog the mouth of the bottle. Cheese cloth, terry cloth or even a coffee filter can be used, he explained.

But don’t jam the cloth too tight, he said. The water won’t be able to flow through as the cloth traps the sediment.

Next he put a layer of activated charcoal in the mouth of the bottle, followed by equal layers of sand and then gravel, which can be found at your local hardware store. Room needs to be left at the top of the bottle to pour in the contaminated water.

“Any medium-course gravel will suffice; you just don’t want it finer than the sand or too big so that it does not trap large particulates,” Cummings said. “The caveat is that water passing through this filter will be much cleaner, but it should still be purified before consumption to destroy any harmful bacteria, pathogens or parasites that are present.”

Another way to kill pathogens is to put eight drops of Clorox into a gallon of water and shake it well, Cummings said. Leave the cap off and let the water sit for about 30 minutes before consuming it.

A natural disaster often damages power sources, leaving homes without electricity. Once again, Cummings turned to the sun for help.

Solar garden lights can be placed on mounts and brought indoors when the power goes out.

Cummings also used an old projection television screen he placed in a wooden frame that he built to create a solar oven that heats to 400 degrees. He found the screen left on the side of the road for bulky pickup.

Once the oven is set up, and a beam of sunlight is being focused through the screen, it heats up instantly, Cummings explained. During a demonstration, he cooked Vienna sausage on the city’s loading dock using his handmade solar oven.

Surviving in a crisis isn’t hard but does take creativity, Cummings said. “We are on an island with limited resources,” he said. “We need to use what’s around us.”