Intermediate 7 minutes
The evolution of regulators: from twin hoses to what you wear today
More than eighty years of refinement on an idea that never changed
The regulator in your mouth does exactly the same thing as the one from 1943. What changed over more than eighty years isn't the principle: it's five design decisions that seem obvious to you today and were argued over one by one at the time.
In this article you'll see how the industry moved from the twin hose to the single hose, how the alternate air source and the submersible pressure gauge appeared, what performance improvements accumulated along the way, and what's still under development.
Every one of those changes answers a specific safety or performance problem. Knowing them explains why your gear has the shape it has, and why certain configurations are considered unacceptable today.
The move to a single hose
The original design mounted the entire mechanism on the tank, behind the neck, and carried air to the mouth through a corrugated tube, returning the exhaled breath through another. It worked, but it had an interesting physical drawback.
Because the valve sat at back height rather than chest height, breathing effort varied with posture: swimming face-down put the valve above the lung and air tended to flow more easily; in other postures, the opposite happened. On top of that, there was the risk of water entering the tubes.
The solution was to split the mechanism into two stages: one on the tank, which reduces cylinder pressure to an intermediate pressure, and another at the mouth, which does the demand-valve work right where the lung is. That's the architecture explained in the article on how a regulator works.
That single-hose design was developed in the early 1950s (the work of Australian Ted Eldred is the usual reference point) and within a decade it completely displaced the earlier one.
And it brought an advantage that turned out to be decisive in the long run: because there was now an intermediate stage with several ports, more things could be connected to the same system. Everything that came afterward depends on that.
Keep reading with full access
This article is part of the full Encyclopedia. A donation from USD 10 unlocks every article, every species photo and the downloadable app, and helps sustain the Scuba Sign Paperless Diving Community project.