After two summer-time attempts at a gravity-fed waterer - and some surprise snow on the ground in October for extra impetus - I've finally designed a waterer that works! Both of the previous waterers were made from 3" diameter PVC pipe, and both resulted in groans from my wife (and secretly from me): it won't stay upright and it's too hard to fill. We located the waterers in the enclosed run because of the nice weather. Now that it's cold, I have to do what I always knew I would have to: move the waterer inside and keep the water liquid and not frozen. Let me just say this is a small city coop. It is raised off the ground, it is 30 square feet, and it is 4' tall inside. This is NOT a human-sized coop, otherwise there would be much different ways to solve the problems of gravity-fed, ice-free waterer design. The water reservoir is obviously located inside the coop for help in keeping it warm. My wife and I are working with precious little space inside the coop, and only have 6 hens who need water. Yesterday I came up with a plan, today I built most of it, and tomorrow I will install it. It's still made from PVC. The water reservoir will be inside the coop, with PVC "Y" fitting at the top - so one portion of the "Y" sticks outside of the coop (through a hole in the wall that will be insulated and caulked to get rid of drafts and unwanted airflow in general). Filling will be done easily from the outside WITHOUT overflow on the inside chicken-drinking opening. How? I put a valve at the bottom of the waterer! Just before the opening that the chickens drink from there is a shutoff valve. At the filling hole I have 3" diameter Oatey test plug, which provides the top-end seal for the gravity-fed design to work. How to fill water: 1. shut off valve at bottom-end (inside coop) 2. unscrew Oatey test plug on top-end (outside coop) 3. fill with water 4. tighten test plug on top-end (outside of coop) 5. open valve at bottom-end (inside coop) Notes: There may be another method of sealing the top other than the Oatey test plug. I haven't found anything that is so easily removed - this uses a wingnut. The bottom-end PVC valve I found has a huge built-in wingnut on the top that controls a ball valve. I wish it were smaller, and am going to continue to search for something a little less space-consuming and ridiculous-looking. We also plan on heating the waterer with heating tape. The heating tape plugs into a grounded extension cord, has a thermostat that rests on the PVC body of the waterer, and will be insulated by 1/2" foam insulation. This may provide some ambient heating to the coop through the heated water: if it's 10 degrees outside, naturally ~20 degrees inside (with the bird's body heat), and the water is ice-free (ie, above 32 degrees, hopefully even warmer), then the water should dissipate heat into the coop and raise the ambient temperature. How much will it raise the temperature? I don't know. I'm betting that we will end up using supplemental heat of some kind when it gets really cold this winter. The entire PVC watering device will be mounted to the inside of the coop using metal strapping, found in the HVAC section of hardware stores. It is a long coil of 3/4" wide flat metal trip that has holes in it. Cut it off at the right length, put a screw through a hole on one side, pull it tight around the waterer, and put a screw into a hole on the other side (screwing into the wall of our coop here). Make sure you pick the right length screw so it doesn't come out the other side. I will also be using a similar setup with our feeder - another PVC-constructed device with a "Y" at the top so it can be filled from the outside. With a feeder sealing isn't required, though some covering on the outside filling end will be required to prevent rain and snow from spoiling the feed. Pictures tomorrow. Thoughts?