Gravity flow systems tend to have extremely low water pressure which creates special curcumstances with drip emitter operation and a lack of watering uniformity. The first drip emitter on a tube will very likely put out a bit more water in 30 minutes than the last drip emitter will. Standard electric actuated irrigation valves will usually not work with these systems due to the low water pressure. To automate them you usually need a more expensive motor-operated valve. Fortunately most people interested using rain barrels aren't interested in anything fancy and just turn the drip system on and off manually.
A barrel set on the ground often works well when the barrel is full of water and then stops working as the water level drops. The solution to this problem is to elevate the barrel on a stand, however to create good water distribution uniformity it is often necessary for the water source (barrel) to be 10,5 meters (yes, that's 35 feet) above the emitters. Height creates water pressure, and the pressure is necessary for good uniformity. When using a rain collection system this kind of height is almost never achieved. We find that most of our customers that choose a rain collection system either do so out of necessity and/or are looking for a greener solution to water their plants and are willing to work within the constraints of the low and uneven pressure of a rain barrel.
We have developed gravity feed kits to help overcome some of these issues. In addition to our clean water gravity kits we offer a line of Drip Irrigation Kits for Dirty Water.
We recommend that you start out slow when setting up your rain collection system and test how well it works. You can then make modifications as needed to your design before investing too much money on materials you might not need. Remember the key to success if you have problems is almost always to raise the height of the barrel. A lot of people give up without trying that simple solution!
If you are new to rain collection or just looking for a new rain barrel check out our selection Rain Barrels.
Standard Gravity Feed Drip Irrigation Kit for Clean Water
Deluxe Gravity Feed Drip Irrigation Kit for Clean Water