Intermediate Pressure (IP) or Interstage Pressure: The Essential Bridge in Diving Regulators


Scuba diving, an exhilarating underwater activity, has captured the hearts of many adventurous souls. To facilitate the experience, divers use specialized equipment that includes diving regulators. Regulators ensure a continuous supply of breathing gas to the diver by reducing high-pressure air from the diving cylinder to a breathable pressure. The intermediate pressure, or interstage pressure (IP), is a crucial component in the functioning of these regulators. This article delves into the concept of IP, its importance, and its role in the diving regulator system.

The Basics of Diving Regulators

A diving regulator is a pressure-reducing device that allows a diver to breathe comfortably underwater. It consists of two primary stages: the first stage and the second stage. The first stage, attached directly to the diving cylinder, reduces the high-pressure air from the cylinder (typically around 200 to 300 bar) to an intermediate pressure (IP). The second stage, connected to the first stage via a hose, further reduces the IP air to ambient pressure, making it suitable for the diver to inhale.

Understanding Intermediate Pressure (IP)

Intermediate Pressure, also referred to as Interstage Pressure or Low Pressure (LP) in this context, is the reduced pressure between the first and second stages of a diving regulator. This pressure is typically in the range of 8 to 10 bar (116 to 145 psi) above the surrounding water pressure, ensuring a constant flow of air to the diver. The IP is essential in the regulator system, as it serves as a bridge between the high-pressure air from the diving cylinder and the breathable air at ambient pressure.

The Role of IP in First-Stage Regulators

First-stage regulators are designed to perform two primary functions: reduce high-pressure air from the diving cylinder and provide a stable IP for the second stage. They are available in two primary designs: piston and diaphragm. Both designs have their merits and drawbacks, but their primary goal remains the same – to supply a consistent IP to the second-stage regulator.

  1. Piston Regulators: These regulators use a simple, robust design with fewer moving parts, resulting in a reliable and easy-to-maintain system. A spring-loaded piston reduces the high-pressure air from the cylinder, while the spring tension maintains a stable IP. The simplicity of the piston design allows for higher airflow rates, making it a popular choice among technical divers.
  2. Diaphragm Regulators: These regulators employ a flexible diaphragm to separate the high-pressure air from the low-pressure chamber. The diaphragm’s movement drives a lever that controls the opening and closing of the valve, maintaining the IP. Diaphragm regulators are less susceptible to contaminants and external environmental factors, making them suitable for cold water and challenging diving conditions.

Importance of IP Adjustment and Monitoring

The proper functioning of a diving regulator depends on the precise adjustment and monitoring of the IP. Regulators should be serviced and checked regularly by a certified technician, ensuring optimal performance and diver safety. During maintenance, the IP is adjusted to the manufacturer’s recommended specifications. A stable and correct IP is crucial in preventing free-flow issues, ensuring that the diver receives the right amount of air at the correct pressure.

Several factors can affect IP, including changes in ambient temperature, diving depth, and the diving cylinder’s pressure. An accurate IP gauge is essential for monitoring the regulator’s performance, enabling the diver or technician to identify any irregularities in the system.


Intermediate Pressure, or Interstage Pressure, is a vital component in the diving regulator system. It serves as the bridge between the high-pressure air from the diving cylinder and the breathable air at ambient pressure, ensuring a continuous and comfortable supply of air to the

diver. The importance of maintaining a stable and correct IP cannot be overstated, as it directly impacts the diver’s safety and the regulator’s performance.

In summary, understanding the concept of intermediate pressure and its role in the diving regulator system is essential for divers and technicians alike. Regular maintenance and monitoring of IP levels can prevent potential issues and ensure that divers continue to explore the underwater world safely and comfortably. The complex interplay of high-pressure air, intermediate pressure, and ambient pressure within the diving regulator is a testament to the marvels of modern engineering, making scuba diving an accessible and enjoyable activity for people across the globe.