Design your own watering system - A system with one or two cups or a large system using up to 210 cups. Inexpensive pressure reducing valve can be used for small system of one or two cups or large systems. Purchase cups, brackets, tubing and fittings for your system. These cups have a spring loaded trigger stem for positive shut off of water. Water flows only when the birds beak is in the cup. No messy wet spots as with nipple drinkers. DESIGNING A SYSTEM - Drink cups require a source of water at a pressure below 5 lbs. PSI which is provided by a pressure reducing valve, or by gravity tanks (less than five feet above drinkers).