I purchased threaded poultry nipples on ebay designed for gravity watering systems. The drip constantly even when installed properly. They're not leaking, they are dripping from the hole where the water is supposed to come out. Is this really as good as it gets? Should they be dripping like that? I assumed water would only be coming out when they were being used but it doesn't seem to stop. It may seem silly to complain about a drip (1-2 drops/second) but when you have 3 nipples in use, that makes quite a mess. HELP?