Poseidon Xstream Black Scuba Regulator Review

Poseidon wasn’t messing around when they designed this regulator. Designed for challenging conditions and even more challenging dives, the Xstream is certified for deep water use up to 200 meters / 656 feet.

This reg is also the only one on the list endorsed by US Navy divers as suitable for Antarctic waters and conditions.

Every other regulator on this list features a downstream demand valve second stage which is the most common design. The Poseidon Xstream, however, has an upstream design.

What Does This Mean?

Regulators feature either a downstream or an upstream demand valve second stage. With a downstream valve, the valve opens with the direction of the gas flow and is closed with a small spring.

But in an upstream design, the valve must open against the gas flow, that is, in the opposite direction. The benefit of this system is that upstream valves are much more resistant to freeflow and unlikely to suffer from issues caused by wear and tear.

When a first stage fails and pushes too much gas pressure to a second stage, a downstream valve is forced into an open position. As you might remember from your initial training, this results in a free-flowing regulator and very rapid loss of air.

In an upstream reg, the same situation results in the valved being forced closed. This effectively stops the freeflow, but it also means that the build-up of pressure may lead to another failure. To counteract this, upstream regs must feature an OPV (over-pressure relief valve) in their designs. This then allows the user to continue breathing from the reg with a minimized gas loss.