Abstract: An automatically operated valve to prevent freezing of water lines. The valve is elongated, having threads on one end to be received in a conventional plumbing tee or the like, or in a threaded opening in a faucet. The opposite end discharges water during dripping, and has a nipple to receive a hose to divert the waste water. A temperature sensitive device is in contact with the water, and includes a tip that projects at high temperatures and retracts at near-freezing temperatures. A plunger in the elongate valve is moved to close a valve when the tip is projected, and a spring within the drip valve urges the plunger to open the valve when the tip is retractable. The temperature sensitive device is carried by the drip valve by mating threads so the position of the temperature sensitive device can be varied through the threaded engagement.