Allows safe expulsion of unwanted air in piping system.

Unique self-guided poppet assures minimal emission of system liquid prior to sealing.

Poppet seals more reliably than ball design; does not deform under pressure like a hollow ball.

Closes at 0 PSI, as long as liquid is present. Valve closes as liquid rises, after virtually all unwanted air is forced out.

Seals bubble-tight at system pressures as low as 10 psi (EPDM seals).