Keeping Water Clean In A Rain Barrel: The Essential Guide


Rain.  It is the source of life, yet it often falls on the landscape and washes away.  Occasionally, forward looking folks, like off grid homesteaders, see the value in that rainwater and store it in water tanks, barrels, bags, whatever they can find to hold water. Rain barrels are great for storing small amounts of water for remote gardens or animal enclosures.

To keep water clean inside a rain barrel, a few things must happen.  The water must be caught from a clean surface, a preliminary filter like a leaf diverter must be installed, chemical treatment is required from time to time and in the most extreme cases, the barrels must be flushed and refilled.

Without proper maintenance of your rain barrels, algae may form, an infestation of water borne insects may occur, the water may begin to smell and your pipes might get clogged.  Let’s dive into how to maintain a rain barrel so that these problems do not occur.

Do Rain barrels need to be cleaned?

Even if you have all of the precautions in place: a metal roof free from leaf debris, clean gutter with leaf guard, a leaf diverter and a screen on the inlet going into the rain barrels, debris can still find it’s way in there.

It is possible for some algae to begin forming as well, even if your tank is opaque.  While some algae will not harm your water, too much of it and you may begin to have issues with clogs in the pipes and even foul smelling water.

It is recommended that your rain barrels are emptied and scrubbed once a year, preferably at the end of summer before the winter rains set it.  This will ensure clean storage of rainwater for many years. 

However, if you ensure the inlet side of your water harvesting system stays clean, you may not have to flush and scrub your rain barrels for a couple years!

How to Clean Rain Barrels

The time has come to clean your rain barrel.  But where to begin?



I used to install rain barrels for Bluebarrelsystems.comOpens in a new tab., a company based out of California that came up with an ingenious way to tie rain barrels together to store water.  If you are in the market for harvesting water with rain barrels, check these guys out.


As part of the installation of the Blue Barrel System, I would offer a follow up tank cleaning one year after installation.  This is how I would clean a rain barrel.

  1. Open the cap in the bung hole of the rain barrel and drain the water.  (The tool for opening the cap can be purchased thru AmazonOpens in a new tab.).
  2. With a long handled scrubber (I used an Electric Scrubber like this one from AmazonOpens in a new tab.), scrub the inside of the barrel.  Eventually I switched to the Sun Joe Pressure WasherOpens in a new tab. which made the job a lot easier.  
  3. Add a cup of bleach along with a gallon of water and stir inside the barrel, trying to cover all of the surfaces.
  4. Drain bleach solution and rinse the barrels.
  5. Ensure the pipes are free from debris, reinstall the rain barrel and fill.

Related: The Truth About Making Money Off GridOpens in a new tab.

How To Eliminate Algae Growth Without Removing the Water

Algae growth can be a common problem in rain barrels.  Luckily there are ways to mitigate it without having to remove all of the water to do it.

  1. Make Sure Your Barrels Are Opaque – Before you even purchase your rain barrels, ensure they are opaque.  Algae needs light to grow.  White rain barrels that are a little transparent provide the perfect conditions for algae growth.

    If all you have are white rain barrels, you can get around this problem by painting the outside of the barrels with a dark color.
  2. Add Bleach – Bleach kills algae.  Add ¼ teaspoon of common household bleach for every gallon of water storage.  If it is raining a lot, you may not have to add any bleach because the water in the barrels are cycling through, but as soon as that rain stops, I’ll add bleach.  If the weather is dry for months at a time, I add bleach 1x per month.

# of GallonsAmount of Bleach
55 gallons2-4 tablespoons
500 gallons1-1.5 cups
1000 gallons3-4 cups
  1. Add Chlorine – Add 4 parts of chlorine to every 1,000,000 parts water.  By adding Chlorine instead of bleach, the water would still be acceptable for drinking or irrigation purposes.  DO NOT combine bleach and chlorine.  Use one or the other.

# of Gallons# of LitersAmount of Chlorine
55 gallons200760 mg
500 gallons1900 liters7600 mg

If the water remains dirty or filled with algae, refer to the step above for cleaning the rain barrels by performing a complete flush.  This should only occur for those tanks not practicing suggested guidelines for how the water enters the rain barrels.

Otherwise, by storing your water in an opaque tank and adding chemical treatment, you can maintain the water in your barrels for a long period of time.


Using Microbes To Clean Rain Barrel Water

A recent study in Scientific AmericaOpens in a new tab. shows that beneficial microorganisms can be used to clean water.  By adding beneficial microorganisms to the water, the microorganisms naturally remove harmful chemicals such as nitrates and ammonia to provide clean water.

Here in Hawai’i, a lot of folks swear by adding a product called BAM MicroorganismsOpens in a new tab. to shock their tanks instead of using bleach or chlorine.  From my experience, the tanks appear as clean as any tank I’ve seen that uses bleach.  Now we have a study from Scientific America to back that up.

Balance the PH Level of Water in Your Rain Barrels

Because rainwater is acidic, it is a good idea to balance the PH level of your stored rainwater from time to time as not to cause corrosion in your system. 

I like to use PH test strips commonly used to check the water in pools to check the water in my rain barrels, then add baking soda until the water is neutral or slightly alkaline.  For a 55 gallon rain barrel you may only need a couple of tablespoons of baking soda for the PH to balance.  In my 3000 gallon water tank I use a whole box per month.

Acid water can cause corrosion on copper pipes, leaving a green residue almost everywhere.  Sometimes it can cause the pipes to leak.  It can also affect the enamel on your teeth in the same way.

Water that is highly alkaline is considered “hard” water.  It tastes bad, leaves spots on glass, can cause stains on clothes and even make your hair look dull.  In the rare instance that your water is alkaline, you can add water softening rock salt or even vinegar to lower the PH.

Even if you don’t drink the water, it is still important to keep the PH level balanced when it comes to other uses of the water.

Related: Off Grid Water Harvesting: How to Install a Rainwater Catchment SystemOpens in a new tab.

Does Rain Barrel Water Go Bad?

Water does not go bad.  In fact, if water is stored in a cool, dark, dry place, away from concrete and harmful chemicals, then it can be stored almost indefinitely.  It can become biologically or chemically contaminated though so it is important to rotate and filter the water before use.

If water does begin to acquire a stale taste, you can simply filter out the taste.  For peace of mind and to be sure harmful bacteria have not colonized your water, be sure to rotate it out from time to time.


Related: Be Sure to test your water every now and then. Get a water quality test kit from Amazon.

WATERSAFE DRINKING WATER TEST KITOpens in a new tab.


Why Does the Water In My Rain Barrel Stink?

It is important to know that your rain barrel is not a closed system.  Bacteria, pathogens, debris, insects and other contaminants can invade your water with ease at any time. 


Normally this is not a problem, but if your water stays stagnant for too long, the combination of these contaminants can cause your water to become foul smelling.

While this is not necessarily harmful to your plants, if the water gets ingested it can cause illness and even death.

How to Keep Rain Barrels from Smelling

The procedure to keep your rain barrels from smelling is the same as you would use for cleaning your rain barrels.  You will either want to drain the barrels and scrub them clean, cycle the water regularly, or add chemicals like bleach or chlorine to keep any smells at bay.

But why are you holding on to your water for so long anyhow?  I know from experience that most folks fail to even use the water they catch in their rain barrels.  They want to save the water so badly that it might not even get used until the dry season is over and the rains start up again.

Don’t let this be you.  Have a strategy to use your water.  Don’t hoard that water too much.  Use it and make room to catch the rain again as soon as it returns.

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Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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