Is my tap water safe after a flood or storm?

When water turns unsafe

After heavy rain, floods, or a burst water main, two risks come up:

• Contamination. Bacteria like E. coli or giardia, sewage backflow, agricultural runoff.
• Sediment and metals. Pipe disturbance loosens rust, sediment, and occasionally lead from old service lines.

The official boil notice

Your local water authority posts boil-water advisories within hours of any contamination event. Check their website or social media. If a notice is in effect:

• Boil tap water for one full minute at a rolling boil before drinking.
• Use boiled or bottled water for brushing teeth, washing produce, and ice.
• Showering is usually fine for adults. Keep eyes and mouth closed.
• Pets need boiled water too.

Brown water

Discoloured water is usually iron, manganese, or sediment, not always dangerous but unpleasant. Run the cold tap for five minutes. If it doesn't clear, ring the water authority. Don't use the hot tap (it draws from the heater tank where sediment settles).

Filters and their limits

Pitcher filters (Brita and similar): Reduce chlorine, taste, some heavy metals. Don't reliably kill bacteria. Useless during a boil notice.

Reverse osmosis: Removes nearly everything, including dissolved metals. Wastes some water in the process. Worth it if you have ongoing concerns or genuinely hard water.

Carbon block filters (NSF 53 certified): Remove lead, chlorine, many VOCs. Good middle ground.

Test if you're unsure

A home water test kit costs $20 to $80 and checks lead, bacteria, hardness, nitrates, and more in 10 minutes. Cheap insurance after a major plumbing event in your area.

Why flooding puts tap water at risk

Floodwater is not clean water. It picks up sewage, agricultural runoff, chemicals, and debris, and during a major flood it can overwhelm treatment plants or get into the distribution network through damaged pipes. Even where the mains supply itself is sound, a loss of pressure during the event can let contaminants be drawn back into the pipes. This is why authorities issue "boil water" notices after floods and storms; it is a precaution against bacteria and other pathogens that may have entered a normally safe supply.

What to do when a notice is issued

If your water authority issues a boil-water notice, follow it exactly. Bring water to a rolling boil for at least one minute, then let it cool, and use that boiled water for drinking, making ice, brushing teeth, washing fruit and vegetables, and preparing food. Boiling kills bacteria, viruses, and parasites. If you cannot boil water, bottled water is the safe alternative. Chemical disinfection with unscented household bleach is a last resort and only works against some contaminants, so it should not be relied on if boiling or bottled water is available.

Private wells and tanks need extra care

If you draw water from a private bore, well, or rainwater tank rather than a mains supply, treat it as contaminated after any flood until proven otherwise. Floodwater can carry pollutants straight into a well head or tank inlet. Do not drink it until it has been tested and, if necessary, disinfected and flushed. Your local health department can advise on testing. When in genuine doubt about any water source after a flood, the safe default is simple: do not drink it, and use bottled or boiled water until the all-clear is given.

Frequently asked questions

How long should I boil water to make it safe?

Bring it to a rolling boil for at least one full minute, then let it cool naturally. At high altitude, boil for three minutes. Boiling reliably kills bacteria, viruses, and parasites.

Can I shower if there is a boil-water notice?

Usually yes for healthy adults, as long as you do not swallow the water, though take care with cuts and avoid it for infants. Follow your local authority's specific advice, which sometimes differs by the type of contamination.

Is bottled water safer than boiled water?

Both are safe. Boiled, cooled tap water is just as safe as bottled for drinking during a notice, and far cheaper. Bottled water is simply the convenient option if you cannot boil.

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