Why you should have a rain barrel (or two)

By Published On: January 24th, 20248.3 min readCategories: Garden, Projects

Rain barrels are a great investment. Here’s everything you need to know (and maybe some stuff you didn’t)

A rain barrel filled to overflowing

One of my 55 gallon rain barrels filled to overflowing during the last storm

Four years ago my wife gave me a couple of 55 gallon rain barrels for Christmas. Back then, I didn’t know too much about rainwater collection, but I did know water here in San Diego’s semi-desert climate is expensive, so any amount of free water was welcome.

In the time since, I’ve learned a lot about collecting and storing rainwater, expanded my storage capacity, and even found some additional uses for it. While the barrels don’t replace the water piped in from my local irrigation district, they do reduce some costs and inconveniences, especially for places on my property where I don’t have a piped-in water supply.

Looking back, it’s hard to believe I worked on the Acre for 25 years before I got my rain barrels. I really can’t imagine the garden without them now. If you’re considering your own rainwater collection system, I highly recommend it. But, before you run out and buy a rain barrel or two, here are the answers to a few questions you might have.

How much water can you collect and will it be enough for your needs?

This is probably the most common question for people considering whether it’s worth investing in a rain barrel. The amount of water you can collect depends on several factors:

  1. The size of your rain barrel(s). Barrels typically range in size anywhere from 20 to over 200 gallons. The 50 gallon range is most common, but you can daisy chain barrels together to increase storage capacity.
  2. Your average rainfall. Here in San Diego, we get around 20 inches (100 cm) of rainfall per year, but nearly all of that comes between December and April, so that’s when we stock up on water. If it rains more often where you are, you can top off your barrels more frequently.
  3. Your roof area. As a rule of thumb, an inch of rain falling on 100 square feet of roof (about 9 square meters) will yield about 60 gallons (227 liters) of water – i.e., 1 sq ft = .6 gallons of water. So, to calculate how much water you can capture, estimate the total square footage of your roof area and multiply it by .06.For example, my roof is about 1,900 square feet, so I should be able to capture 1,140 gallons of water.

Whether this is enough for your needs depends on how you use it. Most water in a household is used indoors for cooking and cleaning, which rainwater isn’t suitable for (except maybe in the toilet). Used in the garden for hand watering, or with drip or soaker irrigation, you can water 100 square feet with 10 – 15 gallons. If you’re using a standard hose, the amount is around 20 gallons.

For us here in the dry, rainless southwest, we’ll use around 60 gallons per month to keep the potted plants, flower beds and greenhouse watered. If you’re in a place that gets rain throughout the year, you’ll probably need less since nature will do some of that watering for you.

What types and sizes of rain barrels are there?

A full rain barrel in the garden

My rain barrels are 55 gallons with a removable top

You don’t need to buy and “official” rain barrel as you can DIY one out of a plastic trash can.

If you decide to go for a purpose-build one, there are all kinds of rain barrels ranging from industrial looking “drum” styles to decorative ones that look like pottery. Additionally, some are completely round, while others have a flat back that allows you to place them up against a wall or the side of your house.

As for materials, you can get them in metal, terra cotta and food-grade plastic. Plastic is the most common, cost-effective, and easy to work with. Prices for these types of barrels range from $50 to $200 depending on the features and construction. The barrels will either have a removable lid (usually with a fine screen to keep debris and mosquitoes out), or a sealed top with a drain inlet.

Most come equipped with hose bib outlets, though if you’re DIYing it with a plastic drum or trash can, you’ll need to cut one and make an outlet with PVC and a hose spigot.

The better rain barrels (in my opinion) also have additional outlets near the top that allow you to connect multiple barrels together to increase capacity, as well as drain off overfill if the barrel is full.

a removable top on a rain barrel

Rain barrels with a removable screened top and connectors on the back so you can daisy chain them together are my preferred kind

Are rain barrels hard to install and maintain?

No. Basic rain barrel setup is super easy. Just make sure the barrel is level (I learned that lesson the hard way) and on a platform like bricks or wood several inches above ground so you can use gravity to drain the water.

A rain barrel up against a house with a drain outlet over it

My upper rain barrel sits on concrete blocks up against the house

If you’re daisy chaining multiple barrels, you might want each barrel in the chain to be slightly lower than the first so the water is gravity fed from one barrel to the next. (I have my main collection barrel at the top of the hill by the house, and a series of three more barrels downhill, connected by hoses. It works great.)

If you live in an area where it’s flat, or you need to move water uphill, you can install a pump pretty easily. There are a number of inexpensive, solar powered ones these days that don’t require wiring and can pump several hundred gallons of water per hour.

As for maintenance, the biggest issue is keeping dirt and debris from the roof, as well as mosquitoes out. I find a fine mesh plastic window screen does a good job at both. To keep algae from forming, make sure the barrel is made from an opaque material and/or kept out of the sunlight. Also, use the water! Algae and bacteria are less likely to form that way.

Is rain barrel water safe to drink?

No. While rainwater is pure, it picks up dirt, debris and other contaminants from your roof and rain gutters on its way to the barrel. The water is perfectly safe for plants, but you don’t want to drink it.

If you’re interested in making harvested rainwater drinkable (potable), there are ways to purify it, but it tends to be complicated. You can learn more about filtering and purifying water from sites like this one.

How much money does a rain barrel save?

This really depends on how much water costs where you are, how much you’re collecting, and how you’re using it. I have a 200 gallon system which, in the grand scheme of things, isn’t a big part of our overall water consumption (we use about 1,500 gallons a month between the house and yard).

However, where I find the rain barrels really save is in the convenience of using it in places where I don’t have water piped in. For me, that’s the greenhouse, the garden shed, and the chicken coop. Being able to tap the barrel rather than dragging hoses or lugging water containers out to remote areas of the yard is a real time saver.

Does a rain barrel require a permit to install?

That really depends on where you live. I can tell you that here in San Diego County, they encourage the use of rain barrels and no permit is required. It may be different where you live, but in my opinion, water that falls on your house is yours, and shouldn’t require permission from your local government.

Other used for rain barrels

One of the best uses for a rain barrel that’s not strictly water collection is as a heating / cooling element for places like greenhouses and shade coverings.

I have a greenhouse where I installed a 30 gallon barrel (ok, it’s a trash can in reality).

A trash can used as a rain barrel in a greenhouse

I re-purposed a trash can as a rain barrel in my greenhouse where it both stores water and acts as a heater at night

It’s in a sunny portion of the greenhouse, so the barrel of water absorbs heat during the day and radiates it back at night. In winter, when the temperatures dip below freezing, the barrel of water radiates heat keeping the air around it 4 – 5 degrees warmer than other parts of the greenhouse. For some of my subtropicals and early seedlings, the heat from the barrel is a real difference maker. Better yet, it’s free!

Yes, you should have a rain barrel!

So there you have it. In my experience, rain barrels are well worth the investment. If you’ve been on the fence about installing your own, get off of it and do it! I guarantee that, like me, you’ll wonder why you waited so long.

Have a thought about this? Leave a comment below

When all your rain barrels are full

Check out the video below. This is the lowest rain barrel in the chain. The hose on the left feeds water from the barrels up the hill, the hose on the right sends it to the barrel in the greenhouse unless it’s full too. Then it empties into the native garden downslope.

A couple days ago the rain came down so fast the barrel overfilled and poured out the top as well as out the drain hoses.

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About the Author

author avatar
Sage Osterfeld
I’m just a guy with nearly an acre of dirt, a nice little mid-century ranch house and a near-perfect climate. But in my mind I’m a landscaper survivalist craftsman chef naturalist with a barbeque the size of a VW and my own cable TV show. I like to write about the stuff I build, grow and see here at Sage's Acre.

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