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No. If water is labeled or known to be non-potable, you should not use it to brush your teeth.
Non-potable means the water is not considered suitable for drinking or other uses where it may enter your mouth. Brushing your teeth counts because you can swallow small amounts of water, even when you spit afterward. EPA guidance treats tooth brushing as a potable-water use, and CDC guidance recommends bottled or otherwise safe water for brushing when water quality is uncertain.
This is especially important with untreated rainwater, questionable well water, flood-affected water, or any storage tank that is meant only for irrigation or other non-potable uses.
Why Brushing With Non-Potable Water Can Be a Problem
It takes very little water to wet a toothbrush or rinse your mouth. That can make the risk seem small.
The problem is that brushing creates direct contact between the water and your mouth. You may swallow droplets without noticing. Water can also contact irritated gums, small cuts, and other sensitive areas.
Depending on the source, non-potable water may contain:
- Bacteria, viruses, or parasites
- Animal droppings or other material washed from a roof
- Sediment and organic debris
- Chemicals
- Metals
- Contaminants introduced by a tank, pipe, hose, fitting, or previous container contents
Clear water is not necessarily safe water. Many contaminants cannot be seen, smelled, or tasted.
CDC specifically advises travelers to brush with bottled or disinfected water where tap-water contamination is a concern.
What Water Should You Use for Brushing Your Teeth?
Use water that is suitable for drinking.
That could be treated municipal water, an appropriate bottled supply, or water from another source that has been properly managed and established as safe for its intended drinking-water use.
If there is a boil-water advisory because of microbial contamination, follow the instructions from the local water authority. CDC guidance commonly calls for bottled water or boiled water that has cooled before brushing teeth during such advisories.
Do not assume that a water source is safe just because it has passed through a household filter.
Different filters address different contaminants.
Can You Brush Your Teeth With Rainwater?
Untreated collected rainwater should generally be treated as non-potable unless the entire system has been designed, operated, maintained, and verified for potable use.
Rain falling through the air may pick up contaminants. Once it reaches a roof, it can also contact:
- Bird and animal droppings
- Leaves and insects
- Dust
- Roofing materials
- Gutters and downspouts
- Biofilm inside pipes or tanks
A screen or first-flush device can improve collected water quality, but neither one makes the water potable.
A first flush is a device or arrangement that diverts some of the first roof runoff from a rain event. This can reduce the amount of loose dirt and debris entering storage. It is a prefiltration step, not a complete water treatment system.
For garden watering, toilet flushing, and some other non-potable uses, untreated or minimally treated rainwater may be useful depending on the system and local requirements. Brushing teeth is different because the water enters the mouth.
What If I Do Not Swallow the Water?
Spitting the water out does not completely remove the exposure.
The step-by-step explanation “How to Tell If Water Is Unsafe to Drink?” connects the measurement to a practical water-safety decision.
Small amounts of water can still be swallowed while you:
- Wet the toothbrush.
- Brush your teeth.
- Rinse your mouth.
- Rinse the toothbrush.
For that reason, official emergency-water guidance includes brushing teeth among activities that require safe water. EPA says properly disinfected water should be used for brushing teeth when normal drinking water is unavailable or unsafe because of microbial contamination.
A safer approach is simple: keep a small supply of drinking-quality water at the sink for brushing.
Does Boiling Make Non-Potable Water Safe for Brushing?
Not always.
Boiling can kill many disease-causing microorganisms. It does not remove every type of contamination.
EPA notes that boiling or disinfection does not remove contaminants such as heavy metals, salts, and most other chemicals.
That distinction matters.
If water has been declared unsafe because of germs and officials have issued a boil-water advisory, boiling may be the recommended solution.
If the concern is a chemical contaminant, fuel, pesticide, metal, toxin, or an unknown substance, boiling may not solve the problem. In some cases, heating contaminated water can make matters worse by concentrating contaminants as water evaporates.
CDC likewise warns that water contaminated with harmful chemicals or toxins cannot simply be made safe through boiling, disinfection, or ordinary filtration.
When the reason water is non-potable is unknown, use a known safe water supply instead of assuming boiling is enough.
Does a Water Filter Make It Safe?
A filter can be one part of a water-treatment system, but the word filter does not tell you what the device actually removes.
For example, a sediment filter may catch particles while allowing microorganisms and dissolved contaminants to pass through.
For showering with non-potable water, it is useful to understand whether another test is needed for the suspected hazard.
A very fine filter may address certain microorganisms but not dissolved chemicals.
Activated carbon may reduce certain chemicals, tastes, or odors depending on the particular treatment system, but it should not be assumed to make untreated rainwater safe to drink.
UV treatment can inactivate susceptible microorganisms when the water and equipment meet the system's operating requirements, but UV does not remove sediment, metals, salts, or most chemicals.
This is why drinking-water treatment should be considered as a complete process rather than choosing one filter and assuming the water is now potable.
What About Stored Rainwater That Looks and Smells Clean?
Appearance is not a reliable test of drinking-water safety.
A rain barrel or cistern may contain clear water while still having microorganisms or dissolved contaminants that you cannot see.
Storage conditions also change over time. Water quality can be affected by:
- New roof debris
- Animal activity
- Tank contamination
- Dirty screens or filters
- Sediment buildup
- Stagnation
- Plumbing changes
- Treatment equipment that is overdue for maintenance
A TDS meter does not settle this question either.
The diagnostic guide “Why Is It Not Advisable to Drink Rain Water?” clarifies when testing or treatment is needed before household use.
Total dissolved solids, or TDS, is a measure related to dissolved minerals and other substances in water. A TDS reading does not tell you whether harmful bacteria, viruses, parasites, or specific chemicals are present. A low TDS reading therefore does not prove that rainwater is safe for brushing or drinking.
What If My Rainwater System Is Intended for Potable Use?
A potable rainwater system needs more than a storage tank and a filter.
Potable means suitable for human consumption. Non-potable means it is not intended or established as suitable for that use.
A system intended to supply drinking-quality rainwater may need appropriate collection materials, debris control, first-flush management, protected storage, staged treatment, suitable plumbing, regular cleaning, maintenance, and water-quality testing.
The treatment arrangement must address the contaminants that can reasonably occur in that particular source.
Current laboratory testing also has an important role. A home test strip, handheld meter, or single water-quality measurement cannot provide a complete assessment of drinking-water safety.
Local plumbing, rainwater-use, and drinking-water requirements may also apply. Where a household plans to use harvested rainwater for brushing, cooking, or drinking, the system should be evaluated as a potable-water system rather than an ordinary rain barrel setup.
What Should You Do If Your Only Available Water Is Non-Potable?
First find out why the water is considered non-potable.
If a public water system has issued an advisory, follow that advisory rather than using a general treatment method. Different advisories can require different actions.
For a microbial boil-water advisory, properly boiled and cooled water may be acceptable when local authorities say to use it. For chemical contamination, boiling may not make the water safe.
If you are dealing with an unknown private water source, contaminated well, floodwater exposure, or untreated stored rainwater, use bottled or another known safe water source for oral hygiene until the water has been properly evaluated.
CDC recommends using safe water for brushing teeth when water safety is in doubt.
Frequently Asked Questions
Can I brush my teeth with non-potable water if I spit it all out?
It is better not to. You can swallow small droplets while brushing or rinsing, and the water has direct contact with your mouth. Use drinking-quality water instead.
Can I brush my teeth with untreated rainwater?
Untreated roof-collected rainwater should generally be treated as non-potable. Roof runoff can contain microorganisms, animal waste, debris, chemicals, and other contaminants. Use a known safe water supply unless your rainwater system has been designed and appropriately verified for potable use.
Can I use boiled non-potable water to brush my teeth?
Only when boiling is an appropriate treatment for the contamination involved. Boiling can kill many microorganisms but does not remove heavy metals, salts, and most chemicals. Follow local instructions during a water advisory.
Can I rinse my toothbrush with non-potable water?
If the toothbrush will immediately go into your mouth, use drinking-quality water to rinse it. This avoids reintroducing questionable water after brushing.
Is filtered rainwater safe for brushing teeth?
Not necessarily. Safety depends on what contaminants are present and what the complete treatment system can remove or inactivate. A sediment filter, carbon filter, UV unit, or other single treatment stage should not automatically be treated as proof that roof runoff is potable.
Does low TDS mean water is safe for brushing teeth?
No. TDS does not provide a complete test for harmful microorganisms or individual chemical contaminants. Water can have a low TDS reading and still be unsuitable for drinking or brushing teeth.
What should I use during a boil-water advisory?
Follow the instructions issued by your local water authority. When the advisory calls for boiling because of microbial contamination, bottled water or properly boiled and cooled water is commonly recommended for brushing teeth.
