Other Safety and Maintenance Concerns

Water stored in any kind of container represents a risk for small children. Children can drown in as little just a few inches water. Additionally, animals both wild and domestic may become trapped and drown in your barrels if uncovered. Therefore, you should never use an open container for rainwater collection. Make sure you have some way to cover the barrel with a screen or a top. Standing water is also where mosquitoes breed best. As the West Nile virus and other diseases are important concerns these days, you’ll need to take appropriate measures to deter mosquitoes from breeding in your rain barrels. It only takes about ten days for mosquitoes to breed, so you should ideally empty the water in less than ten days. You should also use a fine screen over the top of the barrel so the mosquitoes can’t reach the water in the first place.

The type of barrel you use is also important. Make sure it’s a food-grade container that was made to hold liquid. You cannot cut corners and simply use a trashcan because a common trashcan will not withstand the pressure of the water for long. The location of your rain barrel is also important. Make sure you place it on level and stable ground. When your rain barrel is at maximum capacity, it will weigh quite a bit and tipping is risk on un-level ground.

Depending on what part of the country you live in, we recommend disconnecting your rain barrels in the winter if temperatures in your area regularly reach freezing or below. Constant freezing and thawing of the water in your rain barrel may weaken the material or cause cracks. Store your barrels upside down in the winter to keep them clean for future use.

A final bit of advice for all rainwater catchment systems is to always monitor the rain barrels for overflow. If, for example, you leave for vacation for a week and haven’t taken precautions to avoid the overflow of water, you may end up with damage to the foundation of your home or other related problems over time.

{ 19 comments… read them below or add one }

mary wilber May 11, 2010 at 3:52 pm

what can i put in my rain barrels to stop bacteria/mosquito larvae from forming without harming the value of the water?


lars May 11, 2010 at 5:48 pm

@mary W

You can use nontoxic mosquito dunks. These are suitable for fish ponds and horse troughs, so they won’t harm the value of the water.


Alternatively, you can put a goldfish in the barrel, as long as you are always going to keep enough water in the barrel to sustain the goldfish. This one is a higher maintenance kind of way to handle it, because you have the responsibility of keeping the fish healthy.

If you read the comment on the “Safe Rainwater Harvesting Catchments” page, you’ll see how a reader has described how she uses that method with a fish.


spruce September 28, 2010 at 2:44 pm

It gets very cold in the winter where I live. Do I need to empty my rain barrel for the winter or can I leave some water in there so I have some water in the spring? thanks


lars September 28, 2010 at 2:48 pm


I would recommend leaving the drain open when the temperature begins to dip below freezing. Although you might be okay, it’s possible that the water will expand enough when it freezes to crack your barrel, ruining it.


Margaret October 23, 2010 at 8:55 pm

Can you equip the rain barrel with a filtering system so you can drink the water?


steve October 25, 2010 at 1:42 pm

While I am not familiar with a specific filtration system that fits a rain barrel, yes, you can drink the water if it has been purified.


Julie April 4, 2011 at 5:20 pm

How do you purify the rain water?


steve April 5, 2011 at 12:48 pm

@Julie, I assume you me to purify to drink. While it is possible it’s not the best idea. Roofing material, animal droppings and other hazardous items are likely in the water. You would need to get a good filtration system to clean the water for drinking.


Karen May 22, 2011 at 10:29 pm

We live in Seattle and get moss growth on the roof. If we treat the roof with a zinc sulfate powder, for how long (or after how many rain events) should I wait to reconnect my rain barrel? I am of course assuming that the zinc run-off should not go into my rain barrel because the water might be toxic to my plants and veggies?
Thank you.


steve May 24, 2011 at 1:18 pm

@Karen, With the amount of rain you receive in the Seattle area the zinc sulfate powder would likely be washed off within a few weeks, however you may want to wait a month then reconnect your rain barrel and have the water tested to be sure. I doubt after a month the concentration would harm your plants but if it gives you peace of mind have the water tested. There are other treatments for moss you may want to consider. Such as running a few copper wires across your shingles, this is an alternative to chemicals. The wire should be run every 4 to 5 feet horizontally. Something to consider.


Sherry February 21, 2012 at 4:23 am

I just moved to a house that has three plastic barrels already on the location. The a full with what I assume is water – haven’t inspected them very closely. I plan to use two for rain barrels and one for composting. However, I do not know what these barrels were originally used for. Do you think they are still safe to use, and what can I use to clean them?


steve February 24, 2012 at 4:41 pm

@Sherry, It’s up to you, personally I would not risk it. They might be able to be cleaned but not knowing what was in them makes it hard to know what to clean them with.


Kathy Jackson May 6, 2012 at 6:02 pm

I have a rain barrell with water in in. I’m noticing green slime coming out of the water hose that is connected to the rain barrell. Will this hurt the plants? I only use the rain water for watering the yard.


steve May 7, 2012 at 6:16 pm

@Kathy Jackson, No it will likely not hurt you plants but it will eventually clog the hose, you should add some bleach. You can add roughly 1 to 2 teaspoons of bleach to 10 gallons of rain water and it will not hurt anything.


Brian Sweeney June 5, 2012 at 2:03 am

Last year my neighborhood had a rain barrel making workshop. We were provided with retired 55 gal. candy flavoring barrels. My neighbor set his up & claimed that it killed his tomatoes which are doing well this year. My barrel was set & plumbed to the down spout last year, but never plumbed to the garden. As a result it’s been full, but never properly emptied, just overflowed. The water’s murky and has algae around the water line. Of greater concern is a blackish dried residue in the fill screen and all over the top of the barrel. I live in a city neighborhood of flat roofed row houses & my house has a newish rubber roof. Could there be some residue from the roofing materiel that might be harmful to the plant life? Could there be something collecting on and washing from our roofs that we should be worried about? I’ve drained the barrel and would like to activate it this season. What should I do to clean & prep the barrel. Is it possible to have the collected water tested before I water my plants?


Barbara Peterson July 21, 2012 at 12:17 am

I have 2 rain barrels. Using water plants (water lettuce) has kept the water clear. I added Mosquito Dunk about 3 weeks ago..water was still clear. We had some rain on Wed. Wed PM the water was still clear, but by yesterday & noticed white foam on the top of the water. It was been HOT here into 10 90 & 100’s for several weeks. Any suggestions?


steve July 24, 2012 at 1:24 pm

@Barbara Peterson, Short of dropping in some ice cubes, try using the water as much as possible to keep it from going stagnant.


Kari July 31, 2012 at 11:02 pm

I am a math teacher at a middle school in Tampa, FL. I am trying to work with math/science concepts this year and incorporate rain barrels and will be attending a county workshop soon for it. In the meantime, wondering what can be tested cost effectively for the kids to track changes over time such as ph level etc? The will be measuring volume, surface area, geometry aspects of the barrel as well as keeping stats on the changes over time but I don’t want it to get too expensive. I am also unsure what to do with the water collected and plan to speak with admin about this issue but if you have input on that, that would be great as well. Thanks!


steve August 3, 2012 at 1:17 pm

@Kari, The Ph level can be measured with a Ph meter, they range from $10 to $30, and when you done with the water, pour it on the grass, water a tree or plant.


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