ACME DRILL: Good quality brass, lead free and well finished. Installed last night. Well dressed, no leaks. (It would be nice if it was at the highest point in the house. At least above the water heater) This is a bleed valve (one-way valve) to equalize the siphon pressure in the system. It conforms to building codes in many cities. I couldn't verify if it was the code in my area but I pasted it along with the conservator just to cover my bases. Raven - Thank you. to transport such sanitary articles. Some brick and mortar stores only sell the ½ inch version. (All plumbing in and around my house is ¾" in diameter, so I could easily use ¾" female threads instead of buying a ¾ to ½ adapter for the ½" variety. I didn't have any 2. I didn't have to hunt down employees to find the obscure part 3. I didn't have to walk a mile from aisle to aisle to find this part as well 4. I just googled! that you'll need it.