Prevent impure water from flowing back and contaminating the clean water supply with the Anti-Siphon Backflow Preventer. Required by most local health codes when using a potable, and sometimes non-potable water source for your drip system. The atmospheric vacuum breaker has a 3/4 in. FHT connection which threads onto the hose bibb or faucet; 3/4 in. MHT connection on the other side to attach a timer, pressure regulator, or adapter for supply tubing. Removable filter washer blocks particles that can clog emitters. Use the directional arrow on the device to position in the direction of water flow. The Anti-Siphon Backflow Preventer is made of ABS with UV inhibitors.