Is your tap water safe after a flood?

Short answer. Treat tap water as unsafe until your water supplier or health department says otherwise ¹³. Until then, drink bottled water, or water brought to a rolling boil for 1 full minute ¹², and use the same safe water for cooking, brushing teeth, ice and infant formula ¹. Boiling does not remove fuel or chemicals ¹. A flooded private well should not be used until it has been tested ².

Why can a flood make tap water unsafe?

Floodwater is dirty water. The NSW Government warns that sewage and other hazards can contaminate water and debris ⁶, and the World Health Organization notes that high precipitation extremes can result in drinking-water supply and sewerage system failure ⁸. A flood can reach the supply at three points:

• The public system. Supply and sewerage systems can fail when rainfall is extreme ⁸, which is why agencies tie tap water safety to official notices ¹³.
• Your own plumbing. Even after an alert is lifted, NSW tells households to follow the supplier's advice on flushing pipes ⁶, and Vermont's drinking water agency describes flushing as clearing your own plumbing of potentially contaminated water ⁷.
• Private wells and bores. The EPA and NSW give them separate advice from the public supply ²⁶.

Water containing fuel or toxic chemicals cannot be made safe at home by boiling or disinfecting ¹.

Who tells you when the water is safe again?

Your water supplier or local health authority, not your own eyes. FEMA tells returning residents to listen for boil water advisories, because "local authorities will let you know if your water is safe for drinking and bathing" ³. The EPA says to check with your local drinking water utility or health department ².

Agencies differ on the default while you wait:

• United States (CDC, FEMA): follow your health department's recommendations, and during an advisory use only bottled, boiled or treated water ¹³.
• England and Wales (DWI): the mains supply is usually unaffected by flooding and generally safe to drink, but call your water company if the water is discoloured or tastes or smells different, and boil or use bottled water while you wait to hear whether the supply was affected ⁴. If the mains is contaminated, the water company is responsible for providing an alternative supply ⁴.
• New South Wales (NSW Government): a boil water alert means tap water is not safe to drink; if you are concerned about quality, contact your water supplier, council or public health unit on 1300 066 055 ⁶.

If your home flooded and you have heard nothing, use safe water until an official source confirms the tap.

What should you drink in the meantime?

Bottled water first, if it has not been in contact with floodwater ¹³. Otherwise boil tap water at a rolling boil for 1 full minute and let it cool ², or treat it as your health department advises ¹. The Phaenyx guides on boil-water notices and emergency water purification cover methods, altitude times and bleach doses.

Use this safe water for more than drinking:

Three firm limits apply. Boiling and disinfecting cannot make water with fuel, toxic chemicals or radioactive material safe; use bottled water or another source and ask your health department ¹. Never drink water from radiators or boilers in a home heating system ¹. And never drink floodwater, or use it to wash dishes or brush teeth ³.

What about food, dishes and utensils that touched floodwater?

FEMA's rule is short: "When in doubt, throw it out!" Throw away any food, and any bottled water, that has or may have come into contact with floodwater ³. NSW adds food in containers with screw caps, snap lids, twist caps or flip tops, home-canned food, and fridge contents kept above 5 °C for more than 4 hours ⁶.

For kitchenware, the UK Health Security Agency says to clean and disinfect countertops, crockery and cooking items before using them with food, and to discard wooden boards and utensils contaminated by floodwater ⁵. Use a dishwasher only once a qualified technician has cleared it ⁵. Rules for saving commercial cans and pouches, and bleach strengths for dishes, are in the flood preparedness guide.

Do you need to flush pipes, the water heater and filters?

Yes, once the supply is declared safe, and in the way your supplier tells you. NSW Health says to follow your water supplier's advice on flushing pipes after an alert is lifted ⁶.

Vermont's drinking water agency gives a household checklist for when a public water system lifts a boil or do-not-drink notice, written for notices in general, not floods ⁷:

• Cold taps: run each on full for at least 5 minutes; with a long or complex service connection, as in an apartment building, ask the superintendent or landlord about longer flushing times ⁷.
• Ice makers: discard existing ice and make and discard 3 batches (5 if the feed line is longer than 20 feet), then wipe the bin with disinfectant ⁷.
• Water heaters, water coolers, in-line filters: run enough water to replace at least one full volume of all lines and tanks ⁷.
• Disposable filters: replace them, as they may be contaminated, especially carbon fridge filters and pitcher filters ⁷.
• Softeners and reverse osmosis units: follow the manual or the provider ⁷.

A water heater that was itself under floodwater is an electrical or gas appliance first. None of the agencies cited here gives a specific rule for it; follow the UKHSA's approach for flooded appliances and have it checked by a qualified technician before use ⁵.

What if your water comes from a well?

Do not use it yet. The EPA says not to turn on the pump of a flooded well because of the danger of electric shock, and not to drink or wash with its water until it is tested and safe ². In England and Wales, the DWI says to avoid all use of a private supply you think may be affected, and to use alternatives until you have confirmation ⁴.

Agencies differ here. NSW allows an affected domestic bore to be used if the water is brought to a rolling boil, or advises another source such as bottled or rainwater ⁶; the EPA and DWI ask you to wait for testing or confirmation ²⁴. Disinfection and testing steps are in the Phaenyx guide on private wells in an emergency.

What official agencies recommend

• United States (CDC, EPA, FEMA): follow your health department; use bottled, boiled or treated water for drinking, cooking and hygiene; boil 1 full minute; never use floodwater; do not use a flooded well until tested ¹²³.
• England and Wales (DWI, UKHSA): mains water is usually unaffected and generally safe, but report changes and boil or use bottled water until you know; avoid private supplies until confirmed; disinfect crockery and discard wooden boards ⁴⁵.
• Australia (NSW Government): a boil water alert means tap water is unsafe; boil water for drinking, teeth, raw food, ice and pets; follow the supplier's flushing advice ⁶.
• World Health Organization (Europe): high precipitation extremes can result in drinking-water supply and sewerage system failure ⁸.

The main disagreement is the starting assumption: the UK treats mains water as usually safe unless told otherwise ⁴, while U.S. agencies make the official notice the deciding signal ¹³.

Frequently asked questions

Can I shower if my tap water is under a boil notice?

The agencies cited here do not give one shared rule for bathing. FEMA says local authorities will tell you whether water is safe for drinking and bathing ³, so check the wording of your own notice.

Is bottled water from my flooded pantry safe?

No, if it may have touched floodwater. FEMA says to throw away bottled water that has or may have come into contact with floodwater ³.

My tap water looks and smells normal. Can I drink it?

Not on that basis alone. The DWI asks you to report discolouration or changes in taste or smell ⁴, but U.S. agencies make the official notice the deciding signal ¹³. In the U.S., check with your drinking water utility or health department before drinking it ².

Should I replace my fridge and pitcher filters?

Yes, once the water is declared safe. Vermont's drinking water agency advises replacing disposable filters because they may be contaminated ⁷.

Can I mix infant formula with boiled tap water?

The CDC says not to use suspect water for infant formula and to use bottled, boiled or treated water instead ¹. Ask your doctor or health visitor about formula for a young baby.

To check the water risks where you live, see water safety country by country.

Next step: your water plan

The "Water and air" section of your Phaenyx plan lists the water and air risks for your postal code. The Phaenyx Safe app keeps the reflex cards available offline, so the steps above are on your phone even when the network is down. Build your Phaenyx plan.

Sources

1. Centers for Disease Control and Prevention (CDC) — How to Make Water Safe in an Emergency — https://www.cdc.gov/water-emergency/about/index.html (accessed 2026-10-27)
2. U.S. Environmental Protection Agency (EPA) — Flooding — https://www.epa.gov/natural-disasters/flooding (accessed 2026-10-27)
3. Federal Emergency Management Agency (FEMA) — Returning Home After a Flood — https://www.fema.gov/fact-sheet/returning-home-after-flood (accessed 2026-10-27)
4. Drinking Water Inspectorate (DWI), England and Wales — Flooding — https://www.dwi.gov.uk/flooding (accessed 2026-10-27)
5. UK Health Security Agency (GOV.UK) — Flooding and health: advice for the public — https://www.gov.uk/government/publications/flooding-and-health-public-advice/flooding-and-health-advice-for-the-public (accessed 2026-10-27)
6. NSW Government — Staying healthy after a flood — https://www.nsw.gov.au/emergency/floods/recover/staying-healthy (accessed 2026-10-27)
7. Vermont Department of Environmental Conservation — What to do after a Boil Water or Do Not Drink Notice is lifted — https://dec.vermont.gov/sites/dec/files/documents/FlushingofPremisePlumbingfollowingBoilGuidance.pdf (accessed 2026-10-27)
8. World Health Organization, Regional Office for Europe — Floods and health: fact sheets for health professionals (2014) — https://www.who.int/europe/publications/i/item/WHO-EURO--2014-8519-48291-71705 (accessed 2026-10-27)