As an affiliate, we may earn a commission from qualifying purchases. We get commissions for purchases made through links on this website from Amazon and other third parties.
Non-potable water is water that is not intended for drinking, cooking, brushing teeth, or other uses where you may swallow it. It can still be useful around a home, garden, cabin, or property.
Common uses include watering ornamental plants, flushing toilets in properly designed systems, washing outdoor tools and surfaces, vehicle washing, and some types of irrigation. The right use depends on where the water came from, how it was stored, and how much contact people will have with it.
Rainwater should not be assumed safe just because it looks clear. Roof runoff can pick up dirt, bird droppings, chemicals, and other contaminants before reaching a barrel or tank. The CDC recommends matching water quality to the intended use and limiting untreated rainwater uses that could lead to swallowing it.
Good Uses for Non-Potable Water
For most simple rainwater systems, outdoor jobs are the easiest place to use non-potable water.
Watering Ornamental Plants
Stored rainwater can work well for:
- Flowers
- Shrubs
- Trees
- Lawns
- Decorative garden beds
- Other plants that are not grown for food
A rain barrel connected to a hose or watering can may be enough for a small garden. Larger tanks can feed drip lines or irrigation zones if there is enough flow and pressure.
Keep in mind that gravity-fed systems often have much less pressure than a household faucet. A pump may be needed for sprinklers or irrigation equipment that requires higher pressure.
Watering Food Gardens Requires More Care
Using untreated roof runoff on vegetables, herbs, or fruits deserves more caution.
The CDC recommends using public tap water or bottled water, when possible, for plants you plan to eat. Roof runoff may contain germs or chemicals picked up from roofing materials, gutters, animals, and airborne debris.
Do not assume that a screen or sediment filter makes rainwater suitable for edible crops. A screen mainly removes larger debris. It does not provide a complete water-quality assessment.
If you want to use collected rainwater extensively in a food garden, check guidance from your local health department or agricultural extension service.
Flushing Toilets
Non-potable water can be used for toilet flushing in some properly designed systems. The EPA includes toilet flushing among common non-potable water applications.
This is more complicated than running a garden hose from a rain barrel.
An indoor rainwater system may need:
- Separate non-potable plumbing
- Filtration
- Disinfection where required
- A pump and pressure controls
- Backflow protection
- Clearly identified pipes
- An approved method for adding backup water
- Overflow and drainage provisions
Never make a direct connection that could allow tank water to flow backward into your drinking-water plumbing. Cross-connections can contaminate otherwise safe household water.
Indoor reuse rules vary by location. Check with your local plumbing, building, or health authority before connecting a rainwater tank to toilets.
Washing Cars and Outdoor Equipment
Non-potable water can also be useful for washing:
- Cars
- Garden carts
- Shovels
- Mowers
- Trash cans
- Outdoor furniture
- Other equipment that does not handle food or drinking water
Vehicle washing is one of the common outdoor rainwater uses identified in EPA guidance.
A basic screen may keep leaves and insects out of the tank, while finer filtration can help prevent grit from reaching pumps, nozzles, and spray equipment.
Avoid spraying questionable water as a fine mist where people could easily breathe in the droplets.
Cleaning Patios and Other Outdoor Surfaces
Non-potable water may be suitable for rinsing:
- Patios
- Walkways
- Decks
- Driveways
- Fences
- Siding
- Garden containers
This can be a practical way to use older tank water before cleaning a barrel or cistern.
The water still needs to be suitable for the surface. For example, water containing heavy sediment may leave stains or clog pressure-washing equipment.
Dust Control and Similar Property Uses
Larger non-potable systems can supply water for dust control, soil work, and other property maintenance. The EPA lists uses such as dust control and soil compaction among established non-potable reuse applications.
These uses are more common on larger properties than at a typical suburban home.
Uses That Need More Caution
The term "non-potable" covers many different water qualities. Water that is reasonable for watering a tree is not automatically suitable for washing your body or running through household appliances.
Laundry
Some non-potable reuse systems supply washing machines, but this should not be treated as a simple rain-barrel project.
Laundry creates more contact with people than outdoor irrigation does. Water quality, odor, staining, plumbing separation, treatment, and local rules all become more important.
If you are planning indoor laundry reuse, use a system designed for that purpose and check local plumbing requirements.
Bathing and Showering
Do not assume ordinary untreated rainwater is suitable for bathing simply because bathing is not the same as drinking.
Water can enter the mouth, eyes, nose, cuts, and irritated skin while bathing. The CDC recommends regular testing for germs and chemicals when collected rainwater is used for bathing, drinking, or cooking.
A properly designed treatment system may make some rainwater systems suitable for this use, but that is a different level of system from a basic barrel used for the garden.
Washing Dishes or Food
Untreated non-potable water should not be used to wash:
- Plates
- Cups
- Cooking utensils
- Cutting boards
- Fruits
- Vegetables
- Food-preparation surfaces
These uses provide an easy path for contaminants to reach your mouth.
What You Should Not Do With Non-Potable Water
Unless the water has been collected, treated, tested, and managed as a suitable potable water supply, do not use it for:
- Drinking
- Making ice
- Cooking
- Making coffee or other drinks
- Brushing teeth
- Rinsing food
- Washing dishes or eating utensils
Potable means suitable for drinking.
Rainwater is not automatically potable. Even clear water can contain germs or chemicals that you cannot see, smell, or taste. The CDC notes that rainwater may pick up contaminants from the air, roof, gutters, pipes, storage materials, and animal waste.
Factor in risks of drinking untreated rainwater to assess the follow-up measurement that best addresses the initial concern.
Making collected rainwater suitable for drinking is a whole-system project. It can involve appropriate collection materials, prefiltration, treatment for relevant contaminants, current laboratory testing, regular maintenance, and compliance with local health and plumbing requirements.
One filter, UV light, water-quality meter, or test strip should not be treated as proof that rainwater is safe to drink.
Match Water Quality to the Job
A useful rule is to choose the lowest-contact use that makes sense for the water you have.
| Intended use | Typical level of concern |
|---|---|
| Watering ornamental plants | Lower |
| Lawn irrigation | Lower |
| Washing outdoor tools | Lower |
| Rinsing patios or driveways | Lower |
| Vehicle washing | Moderate |
| Toilet flushing | Moderate; plumbing rules matter |
| Laundry | Higher |
| Bathing | Higher |
| Food washing | Not appropriate for ordinary untreated non-potable water |
| Drinking and cooking | Requires a potable-water approach |
These categories are only a planning guide. The actual risk depends on the water source and system.
For example, clean-looking rainwater from a screened cistern and stagnant water from an open container are both technically non-potable, but they should not be treated as equal.
Keep Non-Potable and Drinking Water Separate
Separation is one of the most important parts of a household rainwater system.
Do not connect rainwater piping directly to drinking-water piping in a way that could allow water to flow backward. The CDC specifically recommends keeping rainwater from entering pipes that carry safe drinking water.
If your rainwater system needs automatic backup from municipal water, the connection needs an approved method of preventing contamination. This is a good point to involve a qualified plumber familiar with local requirements.
Indoor systems should also be clearly identified so someone does not later mistake a non-potable pipe or faucet for drinking water.
Keep the Collection System Clean
Non-potable does not mean maintenance does not matter.
Cleaner water is easier on pumps, valves, hoses, irrigation emitters, and storage tanks. Regular maintenance can also reduce odor, sediment, insects, and biological growth.
A typical rainwater system may include:
Gutter Screens
Screens help keep leaves, twigs, and larger debris from entering the tank.
A First-Flush Diverter
A first-flush diverter sends away some of the first runoff from a storm.
The first water washing across a roof can carry accumulated dust, droppings, pollen, and other debris. Diverting part of this initial runoff can improve the quality of water entering the tank. The amount to divert depends partly on the roof area and collection system.
Covered Storage
Keep barrels and tanks covered and protect openings from insects and debris.
The CDC recommends screened openings or other mosquito-control measures for rainwater storage.
Sediment Control
Sediment can settle on the bottom of a barrel or tank. Too much buildup can create odors, clog fittings, and increase maintenance.
Inspect the tank and clean it when buildup becomes significant rather than assuming stored water can remain untouched indefinitely.
Check What Your Equipment Can Handle
Before connecting non-potable water to a pump, hose, filter, or irrigation system, check the whole water path.
Look at:
- Tank outlet size
- Pipe and hose diameter
- Pump inlet and outlet size
- Required flow rate
- Required pressure
- Filter capacity
- Irrigation emitter size
- Elevation between the tank and outlet
- Available electrical power, if using a pump
- Freeze exposure
Flow rate is how much water moves through the system over a period of time, such as gallons per minute.
Gravity alone may be enough for filling a watering can or slowly feeding a garden line. It may not provide enough pressure for sprinklers or household toilet systems.
Adding very fine filtration can also reduce flow. Choose filtration because the intended use requires it, not simply because a smaller micron number sounds better.
Local Rules Still Matter
Rainwater collection and non-potable reuse requirements vary by location.
Outdoor barrel use may be simple in one area, while indoor toilet flushing may require permits, approved plumbing, backflow protection, treatment, or inspections.
Before building an indoor system, check with the local building department, plumbing authority, water utility, or health department. Do not assume rules from another city or state apply to your property.
Frequently Asked Questions
Can I use non-potable water to water my lawn?
Yes, lawn watering is one of the simpler uses for non-potable rainwater. Keep the tank screened and maintained, and make sure any pump or irrigation equipment can handle the available water quality and flow.
Can I use non-potable water in my vegetable garden?
Untreated roof runoff is better suited to ornamental plants. The CDC recommends using public tap water or bottled water, when possible, for plants you plan to eat. If you want to irrigate food crops with collected rainwater, get local guidance based on your collection system and intended crops.
Can I flush my toilet with non-potable water?
It can be possible with a properly designed system. Indoor rainwater plumbing must remain separated from drinking-water plumbing and may be subject to local plumbing, treatment, labeling, and backflow-prevention requirements.
Can I wash my car with rainwater?
Yes, vehicle washing is a common non-potable use. Filtering out grit and sediment can help protect pumps and spray equipment and may reduce spots or debris on the vehicle.
Can I shower with non-potable rainwater?
Do not assume untreated rainwater is suitable for showering. The CDC recommends regular testing for germs and chemicals when rainwater is used for bathing. A bathing system may require additional treatment and maintenance.
Does filtering non-potable water make it drinkable?
Not necessarily. A filter only addresses contaminants it is designed to remove. Drinking-water safety can require several treatment stages, laboratory testing, system maintenance, and compliance with local requirements.
Does boiling make all non-potable water safe?
No. Boiling can kill many disease-causing germs, but it does not remove many chemical contaminants. Water known or suspected to contain fuels or toxic chemicals should not be treated as safe simply by boiling it.
