Rainwater harvesting has grown in popularity for sustainability, off-grid living and reducing demand on a municipal water provider. It can be a practical water source for non-potable uses like irrigation, but drinking rainwater is not generally advisable.
Public health guidance from organizations like the U.S. Center for Disease Control and the Canadian Mortgage and Housing Corporation (CMHC) generally says rainwater is not considered safe to drink because it can pick up contain germs, chemicals and environmental contaminants collected from the air, roofs, gutters, pipes and storage tanks. , and there is no way to guarantee water quality and safety, even with filtration and disinfection.
In this blog, we’ll explain why rainwater is not considered safe drinking water, what can affect rainwater quality during collection and storage and what options can provide more reliable drinking water at home.
What is rainwater harvesting?
Rainwater harvesting involves collecting rain from rooftops through gutters and downspouts and storing it in a rain barrel, a cistern or a rainwater tank for later use.
Rainwater harvesting can support water conservation and help lower a water bill when it offsets non-drinking uses, including outdoor needs like gardening, car washing and more.
Is drinking rainwater safe?
No, rainwater should not be used as drinking water, even if it’s treated. This is because of the broad range of contaminants that could be present — not all of which can be tested for or addressed by typical home filtration options.
For most households with access to treated tap water, it’s safer to use that regulated supply for drinking, cooking, brushing teeth and rinsing food, rather than drinking rainwater. If you do not have access to a safe regulated supply, talk with local public health authorities about safe drinking water guidance for your area.
Even when homeowners add a water filter or UV disinfection, drinking rainwater still comes with risk.
Explore whole house filtration solutions.
The risks of untreated rainwater
The challenge isn’t as simple as addressing just one or a handful of contaminants. It is the number of potential harmful substances and how they vary by location, season, roof materials, system design and maintenance practices.
The risks of untreated rainwater include:
Germs and biological contamination
Germs can enter collected rainwater in several ways. Bird and animal droppings on roofs, insects entering tanks and biofilm inside pipes and filters can all contribute to contaminated rainwater. These risks include microbes such as Giardia, , E. coli and adenoviruses. Some can cause stomach upset, diarrhea, vomiting, fever and other symptoms. The risk can be higher for children, older adults, pregnant people and people with weakened immune systems.
Chemicals and other pollutants
Raindrops form from water vapor in the atmosphere, then fall through air pollution and airborne pollutants. Along the way, rain can absorb pollutants and carry them into a collection system. Vehicle emissions, industrial pollutants, dust and agricultural chemicals can all contribute depending on the environment.
Roof and gutter surfaces can also introduce chemicals. Coatings, sealants and residues can build up in a rainwater tank over time. Some homeowners also repurpose chemical tanks for storage. That is not recommended for drinking purposes because chemical residues may remain and introduce chemical contaminants.
Materials from roofs, gutters and tanks
Rainwater harvesting often starts with roof runoff. Metals such as lead and copper can leach from roofing, gutters, pipes and fittings depending on materials and age. Leaves, dirt and organic debris in gutters can break down in storage, affecting taste, odor and microbial growth. Poorly sealed tanks can allow insects and small animals in, adding both physical and biological contaminants.
Understanding rainwater regulations
Rainwater harvesting is generally allowed in both the U.S. and Canada, but the rules around system setup and allowable uses can vary. In the U.S., regulations often differ by state and sometimes by city or county. In Canada, rainwater harvesting is generally allowed, with municipal guidance sometimes recommending systems such as covered storage and mosquito prevention.
Many jurisdictions encourage rainwater harvesting for non-potable uses like irrigation and toilet flushing as a conservation and stormwater management tool. For most households with access to a municipal supply, the simplest path to safe drinking water is usually tap or well water alongside home water treatment options designed for drinking water, rather than relying on rain water as a primary drinking source.
If you are considering collecting rainwater, check local guidance. For example, the U.S. Environmental Protection Agency has a municipal handbook of rainwater harvesting policies, and Canada’s national housing agency, CMHC, also published guidance on rainwater harvesting systems for homeowners.
The British Columbia Ministry of Health has more in-depth guidance on the treatment of rainwater for potable uses, though it admits “in many situations, harvested rainwater may be best suited for non-potable use only, or as a supplementary source to existing water supplies for the purposes of reducing stresses related to water quality and/or quantity.” In other words, rainwater — even when treated — should not be used as drinking water.
How to use rain water at home
Rainwater harvesting can still be a smart sustainability step. The key is using rain water for the right purpose.
Common non-potable uses for collected rainwater
Most homeowners use rainwater for tasks where drinking water quality is not required, such as:
- Garden and lawn irrigation
- Car washing
- Rinsing tools or outdoor equipment
- Toilet flushing where permitted by local code
These use cases can help reduce outdoor water use and, in some homes, lower your water bill. They also tend to be more easily achievable because they do not require a drinking water treatment plan.
When rainwater should not be used
Collected rainwater is not recommended for drinking, cooking, brushing teeth, rinsing food or making ice. Untreated rainwater can carry germs, pollutants and other contaminants that are difficult to verify and manage consistently without a robust treatment and monitoring program.
Setting up a rainwater harvesting system for safer, more reliable non-potable use
A rainwater harvesting system can work well for non-potable applications when it is designed to limit debris, reduce contamination risk and support ongoing maintenance.
Here’s how you can get started:
1. Design your collection system
If you are collecting rainwater, focus on system design and upkeep:
- Use roof materials appropriate for rainwater harvesting based on local guidance
- Keep roofs and gutters clean to limit debris, droppings and buildup
- Add screens and leaf guards to reduce solids entering the system
- Store water in a covered, opaque rainwater tank to limit sunlight and keep out insects and animals
- Inspect and clean the rainwater tank and components on a regular schedule
These steps can help reduce pollutants and support better water quality for non-potable uses, but they do not make rainwater safe to drink.
2. Use basic filtration for rainwater
Basic water filtration can reduce larger particles and help protect pumps, hoses and fixtures. Typical options for non-potable setups include inlet screens, coarse filters and sediment filters, but they don’t need to catch everything.
Filtration should match the intended use case. For irrigation, filtered rainwater that is free of grit and debris is often the priority.
Disinfection and treatment considerations
Disinfection is often discussed for potable setups because microbes are a major concern. Methods for disinfecting rain water often include chemical disinfectants or UV disinfection units in permanent systems.
Even with filtration and disinfection, rainwater is not a suitable drinking water source for most households because there is no routine regulatory testing available, and home setups do not typically cover the full range of possible contaminants and changing conditions.
Monitor and maintain your system
A rainwater harvesting system requires ongoing maintenance. Inspect roofs, gutters, screens and tanks. Follow manufacturer guidance for pumps and filters.
If a household ever needs to rely on harvested rainwater for more critical uses, work directly with local public health authorities to understand what testing and water treatment steps are required for your area and setup.
Rainwater safety FAQs
Can you drink rainwater if you boil it first?
Boiling can reduce some germs, which can lower certain risks in an emergency. However, it does not address every possible harmful substance that may be present in collected rainwater. If you have access to treated tap or well water, those are generally safer options for drinking.
Does filtering rainwater make it safe to drink?
A water filter can help reduce some particles and improve appearance. It does not guarantee safe drinking water. Rainwater can contain a wide range of contaminants, including microbes and chemicals, and many are not routinely tested or addressed by standard home filtration systems.
What contaminants are most common in rainwater?
Common concerns include microbes from animal droppings and tank exposure, pollutants from air pollution and airborne pollutants, debris from roofs and gutters, and materials that can leach from pipes or fittings.
Can you drink rainwater from a metal roof?
A metal roof can still contribute to contamination through debris, droppings, coatings and gutter materials. Another risk to consider is the full collection path, including the storage tank and distribution system. Rain water safe assumptions based on roof type alone are not reliable.
How Culligan can help
Rainwater harvesting can be a useful water source for non-potable uses like irrigation. When the goal is drinking water, most households are better served by focusing on the water source they already have — whether that’s a privately owned and tested well, or a regulated municipal water supply.
Your local Culligan water experts can help you understand your home water quality and identify options for cleaner, safer, better-tasting drinking water, without the complexity of managing a potable rainwater harvesting system.
For instance, a comprehensive option such as a reverse osmosis system provides filtered water on tap for drinking and cooking. Culligan can also help you explore whole-home filtration solutions to address specific concerns that affect water throughout the home.
Schedule your free test and consultation to discuss your water source, your goals and the right water filtration approach for your home.
