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First stage regulators and their differences

Updated: Oct 22, 2022

No, we're not going to talk about first stage arguing with each other but we just want to take a look at how shall I say, the difference in character.

First stage

There are two types of first stage, the piston, and the diaphragm. In addition, there are also balanced and unbalanced first-stage regulators. Besides the differences in operation, there are also some external differences such as the connections DIN and INT. But also the number of low-pressure ports and high-pressure ports.

The piston first stage regulator

The piston first stage regulator is the simplest by design. There are only a few moving parts and therefore the piston first stage regulator is very efficient and performs very well due to the high flow rate.

P{piston first stage regulator
Piston regulator diagram

As a result, they can be found in the higher segment (extremely well-performing due to efficiency and

the high flow rate) and in the lower segment (fewer parts make it cheaper for the manufacturer to make them).

Due to the continuous developments in the field of materials and CNC machining, there are now models available in the higher segment that are suitable for colder waters. As a result, the piston first stage regulator is becoming increasingly popular in colder water. The Scubapro MK 25 is an example of a high segment piston first stage regulator.

The Diaphragm first stage regulator

The nature of a diaphragm first stage’s design means that it is environmentally sealed.

Diaphragm first stage regulator
Diaphragm regulator diagram

Diaphragm regulators tend to be complex with more parts than a piston regulator and have a

smaller diameter valve, meaning a lower overall volume of air to the second stage.

Because the inside of the first stage is not in direct contact with the outside water, the membrane first stages are less sensitive to cold and dirt. The Scubapro MK 17 is an example of a membrane first stage regulator.

DIN vs Yoke

The first decision when buying your scuba regulator is do I choose a DIN connection or do I prefer an INT (yoke) connection. Both connections have their advantages and disadvantages, let's see what the options are and whether this results in major differences in terms of advantages and disadvantages, but also with regard to safety.

Let's first name the design differences.

DIN (Deutsche Industry Norm):

The first-stage is screwed into the cylinder valve opening.

The O-ring is in the end of the DIN connection.

INT (yoke or A clamp):

The first-stage is placed around the cylinder valve by means of the bracket and clamped at the back by means of a screw to be tightened.

In the following list I would like to mention the differences which mainly relate to the safety of a DIN regulator and why they’re becoming the norm within modern scuba diving.

  • DIN can be used on cylinders with a filling pressure higher than 230Bar/3335Psi.

  • DIN has a more secure closure, so no leaking first stage connection during the dive.

  • DIN first stage are much less bulky than INT first stage and so the risk of bumping and snagging during your dive is much smaller.

DIN and INT cylinder valve
Cylinder valve

There are some locations around the world where yoke is the standard, if these are your daily locations then the choice for an INT first-stage is of course the obvious one. Although there is still a lot of diving with the insert-less INT cylinder valve in these areas, we see more and more cylinder valves where the INT insert can be unscrewed and you therefore have the option of using a DIN first-stage.

Balanced and unbalanced first-stage

Because we would like to go into more detail about this and do not want to make this post too long, we prefer to do this in a separate blog post.

Click here to read the balanced VS. unbalanced first-stage regulators.

Diving on Demand / Scuba Service Tools accepts no liability for the information given in this document.

Our documents are to provide a general understanding of SCUBA diving-related topics, and not to provide specific advice.

Most authorized dealers are able to perform warranty, repair, and service work on your equipment. Availability of sub-assemblies and components, repair parts, specialized tools, maintenance guides, and service manuals does not imply qualification to assemble and/or service scuba equipment. Improper service of dive equipment can lead to serious injury or death.

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