Greenhouse: Greehouse Bizz, 1 by tropicalaria

tropicalaria wrote:
It doesn't look nearly so elegant in practice, but here is the diagram. The elevated tank is the water reservoir, the top pipe is the airline, and the bottom is the water topoff, which is completely submerged in the tank. When the level of the tank falls below the airline opening, then it allows air to get into the sealed topoff tank, releasing water through the bottom pipe. Both of these should be small pipes to prevent a rush of water--1/2" to 3/4". I use an angle-cut pipe fastened to the side of the tank for my airline so that the topoff starts and stops gradually. By closing the ball valves on the airline and topoff you can refill the system from the top, but make sure you close the refill valve before opening the bottom valve again, or the whole topoff tank will dump into the main tank.

The other two types of topoff I've used in the past were solenoid/pump, and siphon. The former system works great until the solenoid sticks, and then everything is flooded and the pump burns out. The latter always seems to collect minute bubbles in the siphon section which aggregate over time and eventually breaks the siphon. I actually had a pump attached to the siphon for a time to periodically flush the bubbles out.