No matter where you live, capturing rain to water landscaping or wash cars is a good way to use less potable water. However, depending on where you live, your rain water catchment system should be sized accordingly. Here are five questions to help you decide how big your rain barrel should be.
If you can collect rain water from 1000 square feet of roof and a typical rainfall is one inch then a 623 gallon barrel will capture most of the typical rainfall. (1000SF x 1/12 feet = 83.3 cubic feet or 623 gallons). Here are five questions you should ask before installing a rain barrel.
- How much of your roof will drain into the barrel?
The size of your rain barrel should reflect the square footage of your roof that feeds the downspout that fills your barrel. It is best to know the correct square footage of your roof by measuring it. If that isn't possible this calculator from Save the Rain will help you get a good idea of how much of your roof will go into the downspout. - How much rain can you use?
Untreated water will stagnate quickly and can become unpleasant. If you can only use 15 gallons a day, then it doesn't make much sense to install a 200 gallon barrel or tank. You can roughly estimate how much water you can use by timing your outdoor watering habits. Time how long it takes to fill up a one gallon jug. It takes about 20 seconds in our house, which means our water flows at three gallons per minute. If I spend 15 minutes watering the tomatoes then I've used 45 gallons of water. - What is the typical rainfall amount where you live?
This can be a bit tricky to determine. If you want to be very scientific about the calculation you can get the daily rainfall totals for where you live and use software like Microsoft Excel to determine what the typical rainfall is. Check the NCDC Online Climate Data site to find your local weather station. I recently calculated the typical rainfall amount for San Salvador, El Salvador. You can download a simple calculator I built here. A less rigorous way to determine the typical rainfall amount is to use a garden rain gauge. Keep an eye on it throughout the year to estimate what typical rainfall. - How frequently does it rain?
If you live in an area where rains are infrequent it might be worth it to risk a stagnant rainwater tank in order to have more water on hand between storms. If you live in an area where rain is frequent, your tank could be smaller because it will fill more often. If that is the case, you may consider draining the tank frequently in order to avoid stagnant water. - Do you need high water pressure?
Depending on the use you find for captured rainwater, you may want higher water pressure. If that is the case, the barrel should be elevated so gravity can make it run a little faster. If you elevate a tank, consider that water weighs about eight pounds. A 55 gallon barrel that is full of water will weigh about 440 pounds. The larger your tank, the heavier it could get and the more likely it will be that it should be on the ground instead of an elevated platform. If you really want some water pressure, consider installing a much smaller tank in a higher place.
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This is a great list. I would add the question, "Where will the overflow valve be dumping?" During heavy rains our barrel fills and the overflow valve dumps water right next to the foundation, which is not what we want.
I live near the beach in Southern California. It does not rain very often, but we get a lot of condensation from the marine layer. Does anyone think it would be worth it to use a rain barrel for the condensation that makes its way into our rain gutters each morning? Would it go stagnant before I could even collect enough to use for watering plants?
notavictorianlady - If there is a way for you to collect the condensation and you have a use for it I think it is worth it. One thing to consider is how clean your roof is and what volume of water you can collect. It is usually a good idea to dump the first flush of a rainfall outside of your barrel because it contains everything that has landed on your roof since the last rainfall. If you can only collect a small amount of water it probably isn't worth the expense of installing a barrel.
Dave, you raise a good point. Check to see that rain water collection is legal in your area.
We made the decision that smaller rain barrels, located in several different locations was the best choice for us. We have a Victorian home with a rather wildly peaked roofline and lots of odd angles--rather than taking in sheer square footage of the roof, we had to account for how much water could accumulate at each downspout.
We installed five rain barrels. When I water, I alternate between the four nearest the back of the house for our gardens, trying to empty them in a roughly even timeframe, and leave the fifth for the potted plants in the front yard. It's worked out extremely well for us. Last summer, despite an unprecedented heat wave, we ran out of water only once and it rained a day later, easily replenishing our stores.
Why would rain barrels be illegal? It seems odd to me that something that saves such a precious resources like water would be illegal.
@Jayzeeberry, I've read that in some municipalities, the water doesn't belong to you just because it falls on your property; instead, it belongs to the water company because after falling it would ultimately end up in their treatment system. I find it kind of crazy, personally. To my way of thinking, even if I first contain the water, it eventually ends up in the ground when I use it to water my plants, right?
Of course, I'd never abide a law that ridiculous, anyway; and since I highly doubt any of my neighbors would ever report me for collecting rainwater, I'm sure my illicit activities would go undetected. But, good thing it isn't illegal to use rain barrels in Illinois.
Wow, I'm impressed -- do people really have rain "barrels" over 55 gallons??? Who knew?
I kind of like the idea of adding rain barrels to my gutter downspouts, with underground pipes or hoses that dump the overflow in areas away from the house as I choose to release it. But to pass local inspection, the builders had to install some kind of traps taking the water into the ground, and I never did hear exactly why or where it is directed -- just know the traps are installed and not easy to tamper with.
Many municipalities it is illegal because of water rights. For some reason the water company owns you.