Overbalanced First Stage

An Overbalanced First Stage (very desirable if you want to dive deep) increases line pressure as depth increases faster than ambient pressure giving greater performance.

As the diver gets deeper the air they breath is compressed and therefore more air is needed to fill the diver's lungs. This is a basic principal taught in the beginner's dive course. Your first stage must be able to sense this outside pressure in order to maintain a steady flow of air to the second stage.

A major difference in the performance of a regulator is its ability to maintain a constant flow at greater depths. All modern regulators sense outside pressure and compensate for the change, however most regulators still have a considerable drop in performance on deep dives as they cannot increase pressure sufficiently to compensate for the high demands at depth.

An innovation only found in the highest performing regulators is called over-balancing. The very same second diaphragm that provides an environmental seal is larger than the internal diaphragm. This means that as you get deeper more pressure is applied to the external diaphragm than would be applied to the smaller internal diaphragm due to the increased surface area. This actually boosts pressure at greater depths significantly improving performance.

Balanced First Stage

• Medium pressure remains constant at 135psi plus ambiant

Over-Balanced First Stage

• Medium pressure increases at a rate faster than ambient
• Increases by two atmospheres by 165 feet
• Helps compensate for denser air at depth