Can I drink water from my water heater in an emergency?

Yes. The water heater tank is often the best backup water source inside the home. Most residential water heaters hold 30 to 80 gallons of treated municipal water. To access it, turn off power or gas to the heater, turn off the cold water supply at the top, attach a hose to the drain valve at the bottom, open the valve, and open a hot water faucet in the house to allow airflow. The first water released may be rusty or contain sediment — let this drain separately, then collect clearer water. Filter sediment and treat before drinking.

Can I use swimming pool water for drinking in an emergency?

Pool water should primarily be used for non-drinking purposes such as flushing toilets, cleaning, and basic sanitation — not for drinking. Pool water contains chlorine, algaecides, stabilizers, body oils, and other chemicals not intended for consumption that are not reliably removed by basic filtration or boiling. Using pool water for sanitation can significantly extend your stored drinking supply. Drinking pool water should only be considered as a last resort when no safer sources are available, and even then requires multiple treatment steps.

Can I collect and drink rainwater during an emergency?

Yes, but rainwater must be treated before drinking. As rain falls it can pick up airborne pollutants, and once it contacts a roof or collection surface it may also collect debris, bacteria, and chemicals from roofing materials. Filter rainwater to remove debris and sediment, then boil or chemically treat before drinking. Rainwater is a useful emergency backup source, especially because even moderate rainfall can fill containers quickly. Local laws may restrict rainwater collection, but during true emergencies access to safe water takes priority.

Can I drink saltwater or seawater in an emergency?

No. Saltwater cannot be made safe to drink through boiling, chemical treatment, or standard household filtration. Removing salt requires specialized desalination methods such as reverse osmosis or distillation, which are energy-intensive and not available in most homes. Drinking saltwater actually worsens dehydration because the body must use more water to excrete the salt than the water it takes in. Without dedicated desalination equipment, ocean water should not be considered a practical emergency drinking source.

What is the safest order to use emergency water sources?

Use the safest sources first and work toward higher-risk sources only when necessary. Tier 1 (safest, minimal treatment): stored water, water heater tank, freezer ice, and toilet tanks without chemical cleaners. Tier 2 (treat before drinking): household plumbing pipes, rainwater, wells and springs. Tier 3 (best for non-drinking sanitation use): swimming pools, hot tubs, dehumidifier water. Tier 4 (higher-risk drinking sources, treat carefully): rivers, streams, lakes, ponds, outdoor snow and ice. Tier 5 (avoid without specialized treatment): saltwater, floodwater, urban runoff, industrial or agricultural runoff.

What Water Sources Can I Use If My Stored Water Runs Out?

Emergency Water Storage for Families

What Water Sources Can I Use If My Stored Water Runs Out?

Even well-planned water storage can run low during long disruptions. When that happens, knowing where to find additional water and how to make it safer can help stretch your household supply much longer than most people expect.

Public health agencies consistently warn that water from sources other than sealed, properly stored containers should be treated before drinking. Clear water is not always safe water.

See more: How do I know if my stored water has gone bad?

Water Sources Inside Your Home

Many homes contain usable water that people often overlook. These sources are usually the safest place to start once stored water runs low.

Water heater tank

Most residential water heaters hold between 30 and 80 gallons of treated municipal water — often the best backup source inside the home because the water has already passed through your public water system.

How to access it:

Turn off power or gas to the heater
Turn off the cold water supply at the top of the tank
Attach a hose to the drain valve at the bottom
Open the valve and collect water in clean containers
Open a hot water faucet in the house to allow airflow

The first water released may be rusty or contain sediment — let this drain separately, then collect clearer water. Sediment can be filtered through cloth or coffee filters before treatment.

Toilet tank reservoirs

The tank behind the toilet bowl (not the bowl itself) typically holds 3 to 7 gallons of clean tap water. This water is usable if no chemical cleaners or blue tablets have been added to the tank.

How to access it:

Remove the tank lid
Scoop or siphon water into containers
Filter debris through cloth or a coffee filter
Boil, disinfect, or use both before drinking

If chemical cleaners were used in the tank, this water should not be consumed. It can still be used for flushing toilets or basic cleaning.

Household plumbing pipes

When the water supply is shut off, some water remains in your home's pipes. The total amount is limited, but even a gallon or two can help.

How to access it:

Turn off the main water valve
Open the highest faucet in the house
Open the lowest faucet and collect draining water

Treat this water before drinking.

Ice makers and freezers

Ice cubes and frost buildup in freezers can provide small but useful amounts of water. Let the ice melt naturally and collect in clean containers. This won't supply large volumes, but it can help stretch drinking water when every bit counts.

Canned goods liquid

The liquid in canned vegetables, fruits, and beans is mostly water and safe to consume. It can help with hydration and provides nutrients. A pantry with a good variety of canned foods may contain one to two gallons of usable liquid — not a replacement for drinking water, but a meaningful supplement.

Dehumidifier reservoirs

Dehumidifiers collect moisture from the air and store it in a reservoir. This water can be used immediately for cleaning and sanitation. If needed for drinking, it should be filtered and disinfected first. It's a backup option, not a primary source.

Freshwater aquariums

Water from a freshwater aquarium can be used right away for cleaning and sanitation. If needed for drinking, it should be boiled and treated first. Saltwater aquariums are not usable as a drinking water source.

Outdoor and External Water Sources

These sources offer larger volumes but require more careful treatment.

Swimming pools and hot tubs

Swimming pools can contain hundreds or thousands of gallons — extremely valuable for non-drinking uses such as flushing toilets, cleaning, and basic sanitation. Using pool water this way can significantly extend your stored drinking supply.

Pool and hot tub water is not considered safe to drink without extensive treatment. In addition to bacteria and debris, these sources often contain chlorine, algaecides, stabilizers, body oils, and other chemicals not intended for consumption and not reliably removed by basic filtration. Pool water should only be considered for drinking as a last resort and only after multiple treatment steps.

Rainwater collection

Even moderate rainfall can fill containers quickly. Rainwater is not sterile — it can pick up contaminants from roofs, bird droppings, and air pollution — so it should always be filtered and treated before drinking. Local laws may restrict rainwater collection, but during true emergencies, access to safe water takes priority.

Natural water sources (rivers, streams, lakes, ponds)

Natural water sources can provide an ongoing supply but require thorough treatment before drinking.

When collecting:

Choose flowing water over stagnant water
Collect upstream when possible to reduce contamination

Recommended treatment steps:

Pre-filter to remove sediment
Use a filter rated for bacteria and parasites
Boil or chemically disinfect before drinking

Avoid water near:

Oily or chemical sheens
Industrial or agricultural sites
Dead animals
Bright blue or green algae, which may produce heat-resistant toxins

Wells and springs

Water filtered through soil can still contain bacteria or chemical contaminants and should be treated before drinking unless recently tested and confirmed safe. During power outages, electric well pumps may not function — plan accordingly if your household relies on well water.

Snow and ice

Clean snow and ice can be melted for drinking water, though it takes a surprisingly large volume to produce useful amounts and requires fuel or heat. Only collect clean white snow or ice from areas away from roads, buildings, and animal activity. Treat melted snow water before drinking.

What about ocean or saltwater?

Saltwater is not safe to drink and cannot be made safe through boiling, chemical treatment, or standard household filtration. Removing salt requires specialized desalination methods such as reverse osmosis or distillation, which are energy-intensive and not commonly available in most homes. Drinking saltwater worsens dehydration and can be dangerous. Without dedicated desalination equipment, ocean water should not be considered a practical emergency drinking source.

Prioritizing Water Sources Safely

Using water sources in the right order reduces risk and conserves effort.

Tier 1 — Safest drinking sources with minimal treatment (use these first):

Stored water
Water heater tank
Ice makers and freezer ice
Toilet tanks without chemical cleaners

Tier 2 — Drinking sources requiring treatment:

Water from household plumbing pipes
Rainwater
Wells and springs

Tier 3 — Best for non-drinking uses (sanitation and cleaning first):

Swimming pools
Hot tubs
Dehumidifier water

Tier 4 — Higher-risk drinking sources (only if safer options are exhausted, treat carefully):

Rivers and streams
Lakes and ponds
Outdoor snow and ice
Waterbed mattresses (may contain algaecides — heavy treatment required)

Tier 5 — Not suitable without specialized treatment (generally avoid for drinking):

Saltwater or seawater
Floodwater
Urban or street runoff
Industrial or agricultural runoff
Water from unknown containers or tanks

Tips for Safety and Preparedness

Treat water from any source outside your stored supply. Even clear-looking water can contain harmful pathogens. When possible, layer treatment by pre-filtering, filtering, and then boiling or disinfecting.

Identify potential water sources in and around your home now — not during an emergency. Practice accessing and treating water so the process feels familiar and manageable when it matters.

Key Takeaway

Most homes contain more emergency water than people realize. With basic treatment knowledge, these sources can help extend your water supply well beyond what's stored.

Stored water remains your primary defense in an emergency. Alternative sources are meant to support your plan, not replace it. Knowing where water can come from and how to use it safely adds confidence and flexibility when disruptions last longer than expected.

Download Our Complimentary Smart Start Guide to Emergency Water Storage

For a printable reference you can keep with your preparedness supplies, download our free Smart Start Guide to Emergency Water Storage.

Sources and References

The recommendations in this article are based on current guidance from trusted public health and emergency preparedness agencies on where emergency water may be found, how to treat it safely, and why certain water sources should be avoided or require layered treatment.

CDC — How to Find and Make Water Safe in an Emergency
Explains how to locate alternative water sources inside and outside the home, why stored and treated water is the safest, and why water from uncertain sources should be treated before use.
FEMA / Ready.gov — Emergency Water Supply Planning
Guidance on planning for water needs, how much to store, and what to do when municipal supplies are cut off.
EPA — Emergency Disinfection of Drinking Water
Explains how to boil and chemically disinfect water, why treatment is necessary for uncertain sources, and why filtration alone isn't enough for pathogens.
American Red Cross — Water Treatment in Emergencies
Simple, step-by-step water treatment methods reinforcing that water of uncertain purity should be treated before use.
NSF International — Emergency Drinking Water Alternatives
Identifies alternate water sources like melted ice, toilet tanks, and rainwater that can be treated for use during emergencies.

Reviewed for accuracy against current CDC, FEMA, EPA, and NSF guidance.

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