How to Clean a Rain Barrel (Step by Step, No Harsh Chemicals)

Clean a rain barrel by draining it fully, scrubbing the inside with a long brush and warm soapy water, rinsing twice, and letting it dry in the sun before refilling. The whole job takes under an hour for a 55-gallon barrel, and you do not need bleach or harsh chemicals for water that goes on ornamental beds and lawns. Clean it once a season, and straight away if the water smells, turns green, or grows slime.

All water in this guide is for non-potable use only: watering ornamental garden beds and lawns, and outdoor cleaning. Rain barrel water is not drinking water, and cleaning never makes barrel water suitable for drinking.

Quick picks

• Fastest clean: drain, brush, rinse twice, sun-dry — under an hour, no chemicals.
• Best brush: a long-handled bottle brush or deck brush that reaches the bottom.
• For slime and smell: warm water plus a little dish soap, then a plain-water rinse.
• Never do: pour bleach or disinfectant in and leave it — it harms plants and soil life.

When Does a Rain Barrel Need Cleaning?

Sign	What it means	Clean now?
Slimy walls	Algae and biofilm building up	Yes — scrub the walls
Green water	Algae bloom from sun and warmth	Yes — and add shade
Bad smell	Stagnant water, rotting leaves	Yes — drain and scrub
Mosquito larvae	Standing water with an open lid	Yes — and fix the lid
Clear water, no smell	Barrel is healthy	No — routine clean is enough

A barrel that smells is not just unpleasant — stale water can harm plants. If the smell is strong, read rain barrel water smells for the cause before you start, so you fix the source as well as the symptom. A clean barrel also lasts longer: grit and algae wear seals and clog the spigot, as our rain barrel maintenance checklist explains.

Watch out: do not clean a barrel by tipping a full one over. A full 55-gallon barrel weighs about 460 pounds — drain it first through the spigot, then tip the last few inches out.

Step 1: Drain and Disconnect

Turn off the diverter or disconnect the downspout first, so no new roof water runs in while you work. Open the spigot and drain the barrel onto a lawn bed or a thirsty ornamental plant — that water is still useful, even if it smells a little. Use a watering can to catch the last of it if the spigot sits above the bottom.

Once the flow stops, tip the barrel gently to empty the last few inches, then move it to a spot where you can work around it. If your barrel is linked to a second one, disconnect the link pipe first — see how to connect two rain barrels for how the link comes apart.

Watch out: never drain a smelly barrel onto a vegetable bed or a pond. Ornamental beds and lawn only — the same non-potable rule as always.

Step 2: Scrub the Inside

Add a few inches of warm water and a squirt of plain dish soap. Scrub the walls and floor with a long-handled brush, working from the top down so dirt falls to the bottom. Pay attention to the water line — that dark ring is algae and biofilm, and it comes back fast if you leave it.

For the bottom corners, a smaller bottle brush or an old cloth on a stick reaches where the big brush cannot. Scrub the lid and the mesh screen too — a clogged screen is how leaves and mosquitoes get in. If your lid is the problem, how to keep mosquitoes out of a rain barrel covers mesh and lid fixes in detail.

Watch out: do not use a wire brush or steel wool on plastic. It scratches the surface, and scratches give algae more places to grip next time.

Step 3: Rinse Twice, Then Sun-Dry

Tip the soapy water out and rinse with clean water, swirling it around the walls. Rinse twice — soap left inside foams on the next fill and can upset soil. A garden hose makes this fast: spray the walls, tip, and repeat.

Then leave the barrel open in the sun for an hour or two. Sunlight dries the inside and kills most of the algae left behind. Do not refill a damp, soapy barrel — the soap smell returns within days.

If the spigot drips or runs slowly after cleaning, the washer may be worn. Our guide on how to fix a leaking rain barrel spigot covers resealing and replacing it.

Watch out: do not use a pressure washer on full power. It can crack thin plastic and force water into seams. A hose on a normal spray setting is enough.

What About Bleach or Vinegar?

You do not need bleach for garden water. Bleach kills soil microbes and can burn plant roots if any residue survives the rinse. Vinegar is gentler, but it is not needed either — soap, scrubbing, and sun do the job.

The one exception is a barrel that held something other than rainwater. If you do not know what a used drum held, do not clean it and use it — do not use it at all. Our best rain barrel for beginners guide explains why only food-grade drums are safe.

Watch out: never mix bleach and vinegar, and never pour either into a barrel you plan to refill the same day. If you ever do use a disinfectant, rinse three times and let it dry for a full day.

How Often Should You Clean It?

Situation	How often
Normal use, lid on, mesh clean	Once a season
Barrel in full sun	Twice a season — sun grows algae
Leaves falling into the barrel	Monthly in autumn
Smell, slime, or larvae appear	Immediately, then check the lid

Cleaning little and often beats one big annual scrub. Five minutes to clear the mesh each month stops most of the dirt that causes smells. For the full seasonal routine, see how to winterize a rain barrel before the cold season, and rain barrel setup if you are putting the barrel back in a new spot.

Watch out: a barrel that needs cleaning every few weeks has a bigger problem — usually a missing mesh, a cracked lid, or full sun with no shade. Fix that, or you will be scrubbing all summer.

Cleaning Mistakes to Leave for Later

Mistake	Why wait	Try instead
Bleach soak for garden water	Harms plants and soil life	Soap, brush, and sun-dry
Pressure washer on full power	Cracks thin plastic	Hose spray and a brush
Cleaning a full barrel	460 pounds — unsafe to tip	Drain first, then clean
Painting over algae stains	Paint peels off dirty plastic	Clean first, then paint

Get the basic clean right first. A barrel that is drained, scrubbed, rinsed, and sun-dried once a season gives clean-smelling water all summer. Once the routine is easy, the rest of the maintenance follows on its own.

Frequently Asked Questions

How often should I clean my rain barrel?

Once a season for normal use. Clean it straight away if the water smells, turns green, or grows slime — and check the lid and mesh, because that is usually the cause.

Can I use bleach to clean a rain barrel?

You do not need to, and it is best not to for garden water. Bleach residue can harm plants and soil life. Warm soapy water, a brush, two rinses, and sun-drying work fine.

How do I clean a rain barrel I cannot reach inside?

Use a long-handled brush through the lid opening, and tip the barrel on its side to reach the bottom. If the opening is too small, remove the lid or the top ring if your barrel allows it.

Why does my rain barrel smell again a week after cleaning?

The cause is still there — usually leaves or sunlight getting in, or water sitting too long. Clear the mesh, add shade, and use the water regularly so it does not sit for weeks.