SPG (Submersible Pressure Gauge) — What It Is and Why It Matters
An SPG (submersible pressure gauge) is a mechanical gauge connected to a high-pressure port on the regulator's first stage that displays your remaining tank pressure in real time. It is the analog alternative to air integration — simple, reliable, and battery-free. SPGs use a Bourdon tube mechanism that has been proven over decades of diving.
SPGs are often mounted in a console alongside a depth gauge and compass, though minimalist configurations clip the SPG as a standalone instrument on a short hose. Many divers carry an SPG as a backup even when using air-integrated dive computers, as a mechanical gauge never loses wireless signal or runs out of battery.
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Frequently Asked Questions
Do I need an SPG if I have an air-integrated computer?
It is not required, but many experienced divers and instructors recommend carrying one as a backup. Wireless transmitters can lose signal, and batteries can die. An SPG provides independent confirmation of your remaining air supply.
How do I read an SPG?
The SPG displays remaining tank pressure, typically in bar (metric) or PSI (imperial). A full standard tank reads around 200 bar (3000 PSI). Plan to end your dive with at least 50 bar (700 PSI) reserve. Most SPGs have a red zone marking the reserve area.
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