Advantages:

When the valve is closed, the valve chamber above the disc (i.e. the outlet side cavity) is empty. Any residual liquid (such as seawater) remaining above the valve disc will naturally drain through the outlet pipe under the force of gravity.

This effectively prevents liquid accumulation, freezing (in cold waters), or corrosion within the valve chamber, whilst also avoiding sedimentation that could obstruct the valve. This is crucial for systems handling ballast water, seawater cooling, bilge water, and similar applications.

Drawing:

Data sheet: