Not sure which type of regulator to choose? Piston vs diaphragm regulators - Learn the key differences between these first stages and how they can affect your dive!
Scuba service technicians aren't the only divers who need to understand how regulators work! Every scuba diver should know the basics before purchasing one.
A regulator set comprises several essential elements:
A first stage - is attached to the tank valve, its only job is to reduce the high pressure gas from the tank to lower pressure before it reaches your second stage, and distributing this pressure to your regulator accessories
A second stage - this further reduces the gas pressure to a breathable level.
A low pressure hose - delivering gas to your second stages.
A high pressure hose - delivering gas to your SPG or transmitter.
As you inhale, the first stage opens, releasing gas from the tank to its chamber. The valves close when the demand ends (between inhalations).
Apeks MTX-RC 50th Anniversary Limited Edition Regulator.
Regulators have two primary methods to address fluctuations in supply pressure, demand, and depth instantly. Diaphragm-based regulators employ a flexible component to accommodate these changes, maintaining consistent outlet pressure and flow in relation to depth. On the other hand, piston-sensed regulators utilize a moving metallic piston to adjust to these fluctuations.
Some divers think that piston regulators are lighter, smaller, and more reliable, robust and sensitive to changes. Some believe they perform better at depth, accommodate greater gas flow, function more reliably in freezing conditions and are cheaper to maintain despite initially being more expensive. Those who prefer piston regulators claim they are a better value for their money than any diaphragm product.
Other divers swear by diaphragm regulators, finding them to be superior in terms of all the above-stated advantages!
Piston vs Diaphragm - Diaphragm Regulators
In a diaphragm first stage, a diaphragm (a flexible disk) covers the intermediate pressure chamber, a portion of the first stage. When the diver breathes in gas from the second stage, the pressure in the intermediate pressure chamber decreases, and ambient water pressure pushes the diaphragm inward. This inward push opens the high-pressure valve to release more gas into the intermediate chamber. When the diver stops inhaling, pressure in the low-pressure chambers rises, and the diaphragm returns to its resting position, which closes the high-pressure valve until the next breath is taken.
There are two types of diaphragm first stages: balanced and unbalanced. A balanced diaphragm regulator is designed to provide consistent airflow regardless of the depth or pressure in the tank. It achieves this by using a balanced design that ensures equal pressure on both sides of the diaphragm, resulting in reliable and consistent performance. An unbalanced diaphragm regulator relies on the pressure of the air in the scuba tank to push the diaphragm, which can result in decreased performance at deeper depths or lower tank pressures. Generally speaking, a balanced diaphragm regulator is more reliable and consistent than an unbalanced one.
Piston Regulators
A piston first stage uses a piston to control the flow of high-pressure gas from the cylinder. When the diver takes a breath, the piston moves downward, allowing gas to flow into the first stage regulator and, eventually, the diver's mouth. As the diver exhales, the piston returns to its original position against the seat, closing the valve and preventing water intrusion. This continuous cycle results in reduced breathing effort and increased efficiency, and piston-style regulators perform just as well on the surface as they do at deep depths.
How do they differ day-to-day diving?
Diaphragm first stages are particularly suited to cold water diving, working in saltwater and water containing a high degree of suspended particles, silt, or other contaminating materials. The only moving parts exposed to the water are the valve opening spring and the diaphragm, which are optimised for these conditions. All other components are sealed off from the environment. A diaphragm is less likely to freeze in the open position or cause a regulator free-flow because of the sealed ambient pressure chamber.
The piston-type regulator can flow more gas because the gas passages are larger than those in a diaphragm. Thus, more gas flow can create icing on the piston in extreme conditions, potentially freezing it in an open position.
Both piston and diaphragm first stages have freezing potential. However, the designs of each greatly reduce freezing potential, ensuring performance in cold water environments.
What this means for you.
It is important to note that there is no right or wrong choice when it comes to selecting a first stage. Some divers simply prefer the breathing experience with a piston first stage. Others value the additional security of a balanced diaphragm first stage in extreme conditions. Both types have their advantages and disadvantages, and the choice ultimately depends on the individual diver's preferences, diving style, and preferred conditions.
If you're interested in buying a regulator one of our experts will be able to help! We will walk you through which regulators are piston and which are diaphragm and how they differ in performance.