How to Filter Rainwater – Step By Step (2023)

Last Updated on April 13, 2023 by Mattias

Rainwater harvesting is becoming more prominent each year. The thought of lower water bills and having a water source is often the first reason for most people to start collecting rainwater. While others just don’t wanna be attached to tap and bottled water.

But how do you filter the rainwater? Does it require a filtration system?

In this article, we will go through everything there is to know about rainwater filtration and the best way to ensure that you got clean water in your home.

Why Should You Filter Your Rainwater?

Rainwater is often very clean due to the natural distillation process it goes through. The problem is all the elements it comes in contact with when pouring down, all from animal feces on your roof or dirty gutter screens.

When the rainwater passes all these “stations” before entering your water storage or rainwater tank, it can contain many harmful bacteria and other substances that aren’t good for you.

Hence, rainwater can be a perfect source of drinking water, but you must filter it correctly. We covered everything there is to know about drinking rainwater in our article: Can you drink rainwater, and is it safe?

List of Potential Contaminants in the Rainwater

Animal Feces

Imagine all the birds, squirrels, and critters on your roof. They can leave traces of feces which are known to contain harmful bacteria like:

  • Salmonella
  • E. Coli
  • Different types of fungi


Under certain conditions, an algal bloom can appear. The algae growth can be hazardous to humans and animals if we consume anything that has been in contact with it due to the toxins inside them.


Be on your guard here; at least some pathogens can be concerning. We’re talking about bacteria, parasites, and viruses. Without filtering correctly, these can all cause severe health problems.

To get rid of them, you must have some disinfection system like:

  • UV light
  • An activated carbon filter
  • Chlorination


You should pay attention if you live in an area with many factories. Because when the rainwater pours down, it may absorb contaminants in the air. It can be smog, chemicals that specific factories are letting out.

You don’t want these chemicals in your drinking water, which must be filtered with a reverse osmosis system or a high-quality whole-house filter.

First Step to Filter Your Rainwater

Your Roof

The first thing you should take a look at is your roof. What the roofing material is made of will determine whether or not your rainwater will be drinkable. 

The best roofing you can have is galvanized or stainless steel. If you got other roofing materials like terracotta asphalt or sponge, your water would have too many harmful substances. 

This makes these kinds of roof materials almost impossible to filter for drinking, so you want to ensure you have a roof that can collect rainwater before it goes down in the storage tank/rain barrel. You don’t want the water to pass any harmful organic material.

Your Gutters 

Having clean gutters makes everything so much easier. Gutters are a familiar spot for debris for pathogens for all sorts of things to accumulate and get into your water supply.

A good tip is to check your gutters at least twice a year, maybe even more, especially if you have more debris in your gutters. 

Clean gutters will also keep the mosquitoes down, which is nice. 

Try to limit as much debris from getting into the water tank as possible by installing leaf guards on the downspouts or other pre-filters on your system. Most people use mesh filters to capture more dirt from the gutters.

Having a clean tank is also crucial when it comes to collecting rainwater. 

Rain Barrel Cover

If you’re using rain barrels to collect rainwater, you should buy a cover since it can prevent the water from debris and mosquitoes from laying eggs—a straightforward but effective method.

Ways to Filter Your Rainwater

UV Water Filter

A UV water filter is the most popular way to filter rainwater into drinking water.   

Ultraviolet light has been approved to turn rainwater into drinking water for the whole house. This system makes tap water, shower water, and kitchen water safe.

It has a UV light that neutralizes the harmful bacteria and pathogens that generally make you sick when you drink untreated rainwater. The filtration process kills those, allowing you to drink cached rainwater safely. 

But it would be best if you still had some pre-filters in the system to get some of the larger particles out before it goes down to the UV filter that kills the bacteria.

Very effective in destroying harmful pathogensYou need to change the bulb every year – it costs $100 
Sometimes the ballast needs to change.  
The system can get dirty, which can make it stop working
The light can get blocked
which means that your water may not be filtered.
UV Water Filter Pros vs. Cons

Advice: Check your bulb twice a year, clean the system every time you check the bulb, then you should be fine.

The system overall is excellent and gives a good quality of your filtered water.

But it takes a lot of power. So if you’re living off-grid, this is something you need to know, so you got the energy for it. 

Carbon Filter

A carbon filter can stop many harmful contaminants from entering your water.

But how effectively it stops anything depends on the pore size of the filter. This is measured in “microns.”

Smaller pore size = more effective filtration ability. But since most viruses are much smaller, a carbon filter can’t stop them from going through. This is why many homeowners use a UV purifier with a carbon filter, a charming combination to eliminate all pathogens.

You can stop microorganisms, sediment,
heavy metals, and chemicals.
You can’t prevent all viruses.
Carbon Filter Pros vs. Cons

Clarify Quantum Disinfection Filter 

The following way to filter your rainwater and make it drinkable is with a Clarify.

This system doesn’t take any power except the pump’s ability to move the water in your house. 

This system is perfect if you’re off-grid, 

Requires no powerFilter exchange costs $299 and must be done every 2 years or 200k gallons of water
Easy to install
It kills 99,99% of all bacteria
No chemicals are needed in the filtration process
Low Maintenance
Clarify Quantum Disinfection Filter Pros vs. Cons

Advice: Use some pre-filters before the water reaches Clarify. 

The system is reliable; you can still drink your water safely if your power goes out. 

Reverse Osmosis

Using reverse osmosis is a very effective way to purify your water, and you won’t probably need any additional methods like carbon filtration or UV disinfection.

You can install the filter under your kitchen sink or use a larger unit to get water for your whole house.

Whole House Filter

A whole-house filter is a good choice if you live in a house where more than one person will use your rainwater.

In some cases, they are expensive but a good investment for large households.

They often use different serval methods to filter your water, but all are packed into one system. A perfect way to filter all the gallons of water that pass through your system.

Other Ways to Filter Water

Other ways to filter water that doesn’t require you to have either a pump or electricity are:

Berky Water Filter 


FAQ Rainwater Collection Filtration

What is a conveyance system?

A conveyance system collects, contains, and provides natural stormwater runoff.

Which is better, carbon or charcoal filters?

An activated carbon filter is better because it’s purer and better quality.

What is potable water?

It’s drinking water that comes from ground and surface sources.

How to Filter Rainwater Summary

I hope you enjoyed this guide about filtering your collected rainwater.

As you discovered, there are many good filters for household use, and it can be a great idea to look over our list carefully before setting up your rainwater system.

So make sure to have clean water before you drink it. Good luck!