This project must be tailored to each application, but the concept is flexible and it will work if the basics that I will take you through here are followed.
Our house and yard are sloped in such a way that I was able to design and install a watering system that keeps a large willow tree and a bird bath supplied with water from mid Spring to mid Fall each year using condensation dripping from the cooling coils of our house air conditioning system. The water is free, installation is less than a day's work, and the costs are minimal. Click on the video to see a summary of how it works.
Step 1: Water Source
The water source for this watering system is the condensation produced by the cooling coils of the air conditioning system in the house. The pipe shown here comes from the collection pan under the air handler for the system and it drips pretty constantly from when we begin to use the system in mid Spring until the weather cools in mid Fall.
Using a 4" to 2" pvc coupling, a short piece of 2" pvc pipe, and a 2" 90 degree coupling, I connected several 8' sections of 2" pvc pipe to reach the willow tree. Of course this section of pipe will be determined by the site in which you are building this system. I buried the pipe and couplings until only about an inch of the 4" to 2" coupling is showing above ground directly under the drip of condensation. Winter time freezing is not a consideration, but small critters crawling down into the pipe is, so I placed a patch of hardware cloth in the coupling. This forms an open joint from the condensation pipe so that if something clogs the 2" pipe to the willow tree, it will not back up the condensation into the air handler under the house. I do not recommend connecting directly to the condensation pipe. This pvc pipe to the tree or shrub to be watered should have a slope of at least a 1/8" per foot.
Step 2: Willow Tree Distributer
On the lower end of the 2" pvc, I used a 90 degree pvc coupling and a short piece of 2" pvc to form a vertical pipe near the base of the plant. Before connecting the coupling, drill a hole the same size as the tubing you will use to continue on to the bird bath. I used 1/2" clear vinyl, but the choice is yours. I used a latex sealer around this tube in the coupling. Do not cover this assembly up because you will be drilling holes in the vertical pipe later.
Step 3: Bird Bath
I used an ordinary concrete bowl and stand kind of fixture, but any will work fine. The critical thing here is that the rim of the bowl of the bird bath must higher than the top of the 90 degree coupling at the willow tree.
Using a laser level or a string level to run from the desired water level in the bowl of the bird bath to the vertical part of the distributer at the tree. This level positioning is necessary because the water in the bird bath should never overflow the bowl. If the water does overflow the bird bath, the tree or shrub being watered will get none of the water. Drill several holes around the 2" pipe where you want the bowl water level to be. Make sure that the holes you drill in the Distributer are all above the outlet tube to the bird bath that you installed earlier in the coupling at the tree.
I have a problem with squirrels chewing anything, so I am in the process of replacing the plastic tube that is above ground with copper line up to the bird bath. The tube in the bowl of the bird bath should go to the bottom of the bowl and to the center to keep the water flowing as it is splashed out and evaporated from the bowl.
When you have the system complete, test it by running water into the top end under the condensation pipe until you see water coming out of the holes in the distributer and then take the tube out of the bath bowl and lay it down on the ground until the water is flowing from the distributer. Placing your finger over the end of the tube, put it over into the bowl. When you release the water, a siphon should start that will get the water over the edge of the bowl. Make sure that water fills the bowl but does not overflow the bird bath. Cover your 2" pvc and the bird bath tube and you are good to go! Enjoy your creation.