Introduction: Gravity-fed Rain Barrel Outlet
I have two rain barrels around my house. I can easily fill watering cans from them for my front ornamental gardens and my kitchen garden to the side of the house. It becomes more laborious to use rain water in my main vegetable garden which is more than 75 feet from the nearest rain barrel. So for years I ran a hundred foot hose from a water outlet behind the house to the garden, watering only every other day because of city water restrictions. Then last year the utility put in water meters to further encourage water conservation during the summer months.
The municipal water is chlorinated and I noticed my vegetables flourished more with rain water (when it rained). I decided to start using rain water for watering them. I first reused large water jugs, but filling and hauling them to the garden was a lot of work.
I could have set up a pump to take water from the rain barrels to vegetable garden, but the property slopes down from the house. I decided to have gravity do the work for me.
Step 1: Determining If You Can Do Gravity Feed
Water flows downhill. Gravity causes it to move. The movement is not hindered by the distance travelled (after all, water travels in streams down mountains to eventually reach the oceans). What facilitates the movement is the height distance between the start point and the end point. The water pressure of that flow (in PSI) can be calculated by multiplying that height (in feet) by 0.433. If you want to operate a conventional spray hose you need at least 30 PSI -- 70 feet in height. A drip irrigation system would require 25 PSI -- just under 60 feet in height.
You need a lot less gain to run water out of a hose spigot into a pail or water can. I'd guess I have about 10 feet height difference between my rain barrel outlet and a standing hose spigot.
A quick way to determine if you can do this: attach a hose of sufficient length to your rain barrel spigot to reach your garden. You can have partner wait to turn on the spigot when you get down to the garden or install a shut-off valve on the other end of your hose that you can open when you get down to the garden, opening the barrel spigot before you go.
In the garden, raise the hose end to the height of the garden spigot you hope to install. Open the valve. Does water readily flow from the hose at that end height? If it does, you can set up a rain barrel gravity feed to your garden.
Step 2: What You Need
- a set up rain barrel collecting rain water, with a spigot to which a hose can be attached
- a hose that can reach from the source barrel to your garden
- a free-standing spigot that is high enough from the ground that you can fit your water can or bucket under it; it should have a shut-off and be connectable to your hose. I used a manufactured one, but it can be simply made from common fittings and some means to position it above ground.
Step 3: What If I Have Two Barrels?
I use two hoses connected together for the barrel in front of the house. I have a shut-off attached to the first hose, so I can disconnect the second hose, attach it to the rain barrel that collects off the back roof, and run it out to the garden without letting out all of the water in the front barrel.
Step 4: Quickly Switch From Hose to Watering Can
Since I use the rain water in each barrel in two garden areas, one nearby and one distant, I need to disconnect and reconnect the hose fairly often. Rather than unscrewing and screwing on the hose each time, I installed a quick connection to the spigot. It has a stop which closes when the hose is disconnected. A spare male connector without a hose attached will open the stop so water will run into a watering can.
A small part like this can easily be lost in the greenery around the rain barrel, so I drilled a hole in it near its threads, secured a piece of aluminum wire (does not rust) to it and attached it to the spigot. It hangs out of the way when the hose is connected and is easily found when I want to set up flow to a watering can.
Step 5: A Better Watering Future...
I just last year decided to build something to store the rain water in the garden ... but that's another Instructable!