By Ben Stallings
Rain barrels have become popular water collection systems, but limitations in capacity and problems with overflow, leaks, debris, and settling have many gardeners struggling to find a more elegant solution.
One solution is to create a self-priming siphon system, which draws water from the bottom of a barrel through a hole at the top, . To do this:
Use a trap to catch any debris before it enters the barrels. A trap is the simplest form of first-flush diverter and has no moving parts.
Use a standpipe to make sure your source of water is higher than the siphon(s). When the standpipe is full, all water overflows from that point, without overfilling the barrels.
Place your siphons (one for each barrel) at differing heights so that they will trip (fill with water, expelling the air bubbles) one at a time, requiring a lower flow of water than would be needed to trip them all at once.
Fit the bungholes that are not occupied with siphons with snorkels that let air in and out above the level of the water in the standpipe. This prevents the barrels from overflowing.
Finally, provide an overflow pipe that is safely away from the house foundation.
For more information, read the full article with diagrams and demonstration video. There is also a simpler design that requires less plumbing, but where the siphons do not prime themselves.