What do you look for in a rain barrel?

[Mark]

I'd like to cut my water bill, so I'm thinking about getting a rain barrel or building a cistern. I have never installed a rain barrel though, so I don't know where to start.

How do you pick the right size? What features are important?

[george]

Originally Posted by Mark

How do you pick the right size?

There's two different ways to look at it - do you want to figure out your roof's rain capacity, or do you want to look at how much water your lawn/garden needs? Either way is a good way to figure out cistern size. Or, you could figure out both numbers and then build a rain barrel system based on whichever number is smaller.

First off, the easy way:

Figure out how much water your garden needs, and build a water catchment system to match that need. Depending on your grass, you'll need 0.1 to 1 inch of water per week. Trees need more water than that - they need about half an inch to 1.5 inches per week. Veggies also need more water - they need 0.5-2 inches per week.

Those numbers aren't particularly useful, because they're not in gallons, right? So, here's a helpful conversion: 1 inch of water over 100 square feet = 62 gallons. If you have a 100 square foot veggie garden, you'll need about 62 gallons per week. That number includes any water that the garden gets from natural rainfall, so you should figure out your average rainfall and subtract it from how much water you expect to use.

Here in Dallas, we get about 34.7 inches of rainfall a year. That's 0.66 inches per week (34.7/52). That's enough for most types of grass, but trees and veggies will need some supplemental water.

Let's say you're growing a 100 square foot veggie garden full of watermelons that need ~1 inch of water per week. The sky provides about 41 gallons (0.66 inches x .62) so you need a rain barrel to make up the extra 21 gallons a week. It usually rains at least once every 3 weeks, so use the rule of 3 and get a rain barrel 3 times the size of your weekly needs (ie; a 60 gallon rain barrel).

Here's some more info about figuring out watering needs for trees (it explains how to measure caliper inches):
Caring for My Tree

Then, there's the complicated way:
(yes, there's an even more complicated way)

Here's how to figure out roof capacity:
http://www.ose.state.nm.us/water-inf...-Chapter-3.pdf

In case the link isn't working: start by figuring out the square footage of your roof (length x width). Multiply that number by 0.62 to find out how many gallons of water your roof will catch during 1 inch of rainfall.

So, a 10 ft x 10 ft building (like your garden shed) would generate ~62 gallons of water every time it collected 1 inch of rainfall.

Then, a couple rules of thumb come into play. Take the number you figured out, and multiply it by 80% of the average rainfall in your area (this throws out the outlying numbers). If you live in an area with steady rainfall throughout the year, divide that number by 3. If you live in an area with heavy rainfall in the spring and hot, dry summers, divide that number by 2.

Let's say that 10x10 building is located in Albuquerque, where they get an average rainfall of 8.66 inches per year:
8.66 x 80% = 6.93 inches
10 x 10 x 0.62 x 6.93 = 429.66 gallons. Divided by 3 = 143.22 gallons

That's three 50 gallon barrels, or two 80 gallon barrels. You can connect the barrels together to add capacity - when the first one fills up, it will overflow to the next one in the series.

[george]

Okay, I may have gotten a bit long winded there.

How about this - here in Dallas, we need a 60 gallon rain barrel for every 100 square feet of garden. Or, a 50 gallon rain barrel for every 3 trees.

[Mark]

Thank you. Now I need to find where I put my Ti-86 and do some measurements... I'm going to start by finding out how much it rains in my area, so I can estimate how much water my roof will produce.

Now that I know how to calculate rainfall and water needs, what are the must-have features in rain barrels?

[MasterComposter]

1. Some kind of mosquito proof screening where the water comes in. Most commercial barrels have this.

2. A safe top design that prevents a pet or child from sitting on top and falling in and drowning. Most commercial barrels have small holes on top that lets water in easily, but not large objects. This is why it is unsafe to use an open trashcan to collect rainwater.

3. Overflow system. Where water can flow away when the barrel fills up, to prevent flooding your foundation.

4. Spigot and/or drain. So that you can get the water out.

Those are my votes.

Check out the Rain Barrel Guide!

[starcandy]

The mosquito proof screening and a sealed cover to protect anyone (or anything) from falling in is a must for me. Since the water here would be stagnant, it's a prime breeding spot for such pests, and quite dangerous if you have any children at home.

[fleurdelys]

Well, if you're in a budget and have these items lying around the house, you can try making your own water barrel with the features you want.

Make a Rain Barrel to Save Water

I never thought it would be that easy.