Dual action low head isolation valve

A dual action low head isolation valve for venting gasses in a plumbing system, the valve comprising:

• a valve body with a ball valve seat located on an input side of the valve;
• a first ball positioned in said valve body, the first ball being engaged with said valve seat when there is no pressure differential between said input side and an output side of the valve, wherein the first ball is configured to maintain a seal at the valve seat when a pressure inside the plumbing system is less than or equal to an outside ambient pressure and the first ball is configured to lift from the valve seat to vent gas to the outside when the pressure inside the plumbing system is greater than the outside ambient pressure;
• and
• a second ball and a second ball valve seat positioned in a fresh air pipe which is arranged in parallel with the valve body, whereby said second ball permits fresh air to ingress into the plumbing system, wherein the second ball is configured to maintain a seal at the valve seat when the pressure inside the plumbing system is greater than or equal to the outside ambient pressure and the second ball is configured to lift from the valve seat to permit fresh air inside the plumbing system when the pressure inside the plumbing system is less than the outside ambient pressure,
• wherein the first ball is housed in a first cylindrical housing and the second ball is housed in a second cylindrical housing, each of the first and second cylindrical housings having a valve seat at a lower end thereof upon which the first and second balls, respectively, seat,
• the first cylindrical housing is connected at both ends to input pipes of lesser diameter than a diameter of the first cylindrical housing, and the second cylindrical housing is connected at both ends to input pipes of lesser diameter than a diameter of the second cylindrical housing,
• longitudinal axes of the first and second cylindrical housings are oriented parallel to one another and adjacent to one another, and the second cylindrical housing is connected, via connecting pipes, including at least a first connecting pipe and a second connecting pipe, to the input pipes of the first cylindrical housing, and
• an upper end of the second cylindrical housing is connected to the input pipe at the lower end of the first cylindrical housing by the first connecting pipe and the lower end of the second cylindrical housing is connected to the input pipe at the upper end of the first cylindrical housing via the second connecting pipe.