On this page
- What is a rain barrel?
- What are the advantages of a rain barrel?
- How much water can I save?
- How much water will my roof produce?
- Where can I buy a ready-made rain barrel?
- How can I make a rain barrel?
On other pages
- Rain Barrels: Small Investment, Big Benefits Video - describes all the benefits of a rain barrel
A rain barrel is a system that collects and stores rainwater from your roof that would otherwise be lost to runoff and diverted to storm drains and streams. Usually a rain barrel is composed of a 55 gallon drum, a vinyl hose, PVC couplings, a screen grate to keep debris and insects out, and other off-the-shelf items. A rain barrel is relatively simple and inexpensive to construct and can sit conveniently under any residential gutter down spout.
Lawn and garden watering make up nearly 40% of total household water use during the summer. A rain barrel collects water and stores it for when you need it most -- during periods of drought -- to water plants, wash your car, or to top a swimming pool. It provides an ample supply of free "soft water" to homeowners, containing no chlorine, lime or calcium making it ideal for gardens flower pots, and car and window washing.
A rain barrel will save most Mid-Atlantic homeowners about 1,300 gallons of water during the peak summer months. Saving water not only helps protect the environment, it saves you money and energy (decreased demand for treated tap water). Diverting water from storm drains also decreases the impact of runoff to streams. Therefore, a rain barrel is an easy way for you to have a consistent supply of clean, fresh water for outdoor use, FREE.
The amount of water saved with a rain barrel really depends on the storage volume of the rain barrel, how often it is drawn down and how often it is filled back up by rain fall. For example, if you received enough rain to fill a typical 55 gallon rain barrel each week (see information below) and you empty the rain barrel once a week from mid-April to mid-October you could save up to 1300 gallons over that time (55 gallons times 24 times = 1300 gallons).
Generally speaking each rainfall event that falls on a roof will likely produce far more volume than can be captured in a typical 55 gallon rain barrel i.e. even a small amount of rain falling on a small roof will quickly fill a typical rain barrel. Most manufacturers provide ways to connect individual barrels in series to increase storage capacity. In addition, larger rain storage tanks are available for sale and can be considered based on your needs. Below is an example calculation that shows a 1 inch rain falling on a roof with a 10 foot by 20 foot horizontal footprint would produce 125 gallons of water. (Well over 90% of 24-hour precipitation events in the Mid-Atlantic produce less than 2 inches of rain.)
Example Rainfall to Roof Runoff Calculation
(Feet of Rain) X (Roof Width in Feet) X (Roof Length in Feet) = Gallons of runoff (Gallons per cubic Foot) 0.08 X 20 X 10 = 125 7.4805Notes
- Divide inches of rain by 12 to convert to Feet of Rain
- Roof Width and/or Roof Length must be converted to horizontal distances
Rainfall to Roof Runoff Calculator
You can also download our Excel spreadsheet calculator that will allow you to figure out how much water your roof will produce for different rainfall amounts. This calculator can also be used to show you how much water runs off impervious surfaces around your home during a rainfall event. This information can help you design a rain garden or other area to “slow it down, spread it out and soak it in”.
- Rainfall to Roof Runoff Calculator (XLSX) (11.2K, Download Microsoft Excel Viewer)
- Rainfall to Roof Runoff Calculator Formulas (PDF) (1pp, 55.6K)
Daily precipitation observations and gage measurements for the Mid-Atlantic Region are available from the National Weather Service Middle Atlantic River Forecast Center Daily Precipitation or Ohio River Forecast Center web sites.
Ready-made rain barrels can be purchased from a number of companies, including hardware stores and garden supply stores. In addition, local governments sometimes offer them for a reduced price as part of their environmental education programs.
- How Can I Make a Rain Barrel? (1 pg, 435K)
- Build Your Own Rain Barrel (PDF) (2 pp, 188K)
- Step-by-Step Guide: How to Build a Rain Barrel, City of Lincoln, Nebraska
- Maryland Environmental Design Program - Build a Simple Rain Barrel
- or, see below:
- 1 - 55 gallon polyethylene plastic barrel (Plastic barrels or drums may be available for free or low cost from commercial car washes, bottling companies or other food businesses that use liquids.)
- 1 - 10 foot length of 2 inch PVC pipe
- 1 - 2 inch PVC elbow
- 1 - 2 inch female threaded by 2 inch PVC
- 1 - 2 inch male threaded by 2 inch pipe
- 1 - tube silicone sealer/cement
- 1 - 1/2 inch female threaded silcock (aka
outdoor faucet or hose bib)
- 1 - 1/2 inch threaded bushing
- 1 - 1/2 inch female threaded socket
- 1 - roll teflon tape
- 1 - 1 foot by 2 foot piece of old or new
- 1 - 1 gallon plastic bucket, tub or flowerpot
- 4 - cinder blocks
- Optional - paint to match your house color
- Jig Saw
- Power Drill with 3/4 inch Spade Bit
- Pipe Wrench and Pump Pliers
- Screw Driver
- Hack Saw
- Tape Measure
Step 1 - Inflow - Cut a hole in the top of barrel to allow rainwater to enter the barrel and to access the inside of the barrel. The hole should be just large enough to snugly fit the 1 gallon plastic bucket, tub or flowerpot. The bucket will be used to support a screen to keep mosquitoes and debris out. Cut a 3/4 inch hole in the bucket.
Step 2 - Spigot - Drill a 3/4 inch hole close to bottom of the 55 gallon barrel. (Don't drill the hole too far down inside the barrel where you can't reach it from the access hole on top or else you may need the help of a friend with very long arms!) Put teflon tape on the 1/2 inch bushing and thread it into the silcock or hose bib. Now carefully thread the other end of bushing into the 3/4 inch hole in bottom of barrel. It should fit snugly in the hole and cut threads in the plastic as you screw it in. Now unscrew it from the barrel, apply teflon tape to the threads of the bushing and apply silicone to the outside of the flange on the silcock. Screw it back into the hole and into a 1/2 inch socket on the inside of the barrel.
Step 3 - Down Spout Modification - Prepare the area under the down spout where you want to install the rain barrel. Remove the old down spout and splash block and level the area where the barrel will sit. Place the concrete blocks so they are sloped slightly downward away from the house. Set the barrel on the blocks. With a hacksaw cut the down spout so it is just long enough to fit into the bucket on top of the rain barrel.
Step 4 - Overflow - You should provide an overflow for water if the barrel fills to the top. With a jig saw, cut a hole in the side of the barrel large enough to fit the 2 inch male threaded by 2 inch pipe adapter. Place this fitting inside the barrel and thread it into the 2 inch female threaded by 2 inch PVC elbow on the outside of the barrel. Seal with silicone. Cut a length of 2 inch PVC pipe long enough to reach the ground. Attach a 2 inch PVC elbow to the bottom of this pipe and cut another length of 2 inch pipe to connect to a splash block.