Over twenty years of field operation, research, development and engineering enhancements have combined to make the Tideflex TF-1 Check Valve a very reliable check valve. The bill is formed into a curve that returns to a closed position every time, achieving the tightest possible seal for backflow operations, particularly at low flow rates. The eccentric, flat-bottom design allows installation where the invert of the pipe is close to the floor. The engineered spine provides long-term performance while handling water weight.