How the water stops, and how much you need
There are two different problems. In one, water still comes out of the tap but may be unsafe, and your municipality issues a boil-water or do-not-consume advisory. In the other, nothing comes out: a main has broken, pumps have lost power, or on a private well the pump has no electricity.
The Government of Canada's planning figure is about 4 litres per person per day for drinking, food preparation, hygiene and dishwashing. For a family of four that is 48 litres for 72 hours and 224 litres for two weeks. Add water for pets, around 4 litres a day for an average dog and 1 litre for an average cat.
Before: store some, and be able to treat more
Unopened commercially bottled water is the simplest emergency supply. If you fill your own containers, use food-grade ones, clean and sanitize them first, label them with the date and keep them somewhere cool and dark, away from fuel and solvents. Never reuse a container that held chemicals. Check stored water at least once a year and replace it.
Past a couple of weeks, storage alone stops being practical in most homes, and the sensible approach is storage plus treatment. The Home Water Kit combines 80 litres of stackable storage, which is five days for a family of four at the federal figure, with a gravity filter and purification tablets.
Plan for the toilet as well. Without running water it will not refill, and a simple sanitation kit keeps the household clean.
During: follow the advisory you have been given
Advisories are not interchangeable, so read the wording.
- Boil-water advisory: bring water to a rolling boil for one minute, let it cool, and store it covered. Use boiled or bottled water for drinking, brushing teeth, washing produce, making ice and preparing infant formula.
- Do-not-consume advisory: the concern is usually a chemical. Boiling does not remove chemicals and can concentrate them. Use bottled or stored water only.
- No water at all: drink stored water first. If you must use rain, lake or river water, filter it and then disinfect it, or boil it.
- Ration by keeping drinking water separate, and use lower-quality water for flushing.
Common mistakes
Treatment methods are often credited with more than they can do. These limits matter.
- Assuming a filter removes everything. Most portable filters remove parasites and bacteria but not viruses. Where sewage may be involved, as in a flood, follow filtration with disinfection or boil the water.
- Expecting any portable method to remove chemicals. Boiling, tablets and standard hollow-fibre filters do nothing for fuel, pesticides or metals.
- Rushing tablets. Chlorine and iodine do not kill Cryptosporidium. Chlorine dioxide does, but it can need up to four hours of contact, longer in cold or cloudy water. Follow the packet.
- Letting a filter freeze. A hollow-fibre filter that freezes while wet can be damaged with no visible sign. Store filters indoors in winter.
- Storing water and forgetting it. Date every container and put a yearly reminder in your calendar.