Rain Barrel Tip: What to do with sediment in your rain barrel

In this video, Lars answers a question from one of our readers where she asked,

“I have been collecting rain for my garden for the past two years. I was wondering what the best treatment is to keep the mold away. At the bottom of the barrel, it becomes black fairly quickly. Will moldy water hurt my garden?”

This is a great question and something that concerns a good number of people.

The main thing we wanted to point out is that it is not actually mold, but instead is merely sediment that has settled in the bottom of your rain barrel. The black “gunk” that builds up in the bottom of your rain barrel could be from leaves, dirt or other various debris from your roof that washes down into the barrel. Even with a screen on top of your barrel, this debris can still slip through and settle at the bottom.

This sediment will not hurt your garden, and it is okay if the water is not perfectly clear.

One way to get rid of the sediment is to simple rinse out your rain barrel at the end of the season.

Thanks for a great question, Susan. We hope this cleared some things up for you.

If you have a question about rain barrels, we’d love to hear from you!


George April 24, 2010 at 4:10 pm

I’ve been using rain barrels for a couple years. We have 2 connected so have 130 gallons after a good rain and use it for watering our plants. This spring, I noticed a stale smell in the water. Is there something natural that we can add to the rain barrels to sweeten the water without hurting the plants? They are never really empty anytime during the year so we don’t ever rinse them out.

steve May 19, 2010 at 5:11 pm


Bleach will help with this problem.
I recommend just a few tablespoons full of bleach at a time. This should help!

Sal October 11, 2010 at 12:43 am

This is the first year for my rain barrel. I have been using a watering can to water my garden and plants. This can be tedious. Any suggestions to increase the efficiency in using the water. Thanks.

steve October 25, 2010 at 1:44 pm

@Sal, Most rain barrels have a drain valve at the bottom, try attaching a drip hose and run the hose out to your garden or plants. This will allow the water to slowly drain into your garden without you having to shuttle the water to the plants.

don barnhart November 10, 2010 at 8:52 pm

i want to setup my downspouts from the house gutters to drain the rain water into two rain barrels and use that to keep the pool at the right level and any additional waters for plants/grass watering. do most rain barrels come with a standard drain on the bottom that i could attach a water hose to?

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