Whether you are a seasoned or a newly certified diver, having a good knowledge of the different types and uses of scuba tank valves is essential. No matter if you are buying or renting your scuba equipment, knowing the details about different types of valves ensures will allow you to identify the right valve based on your dive location, environmental conditions, and type of diving.
In this post we will cover the full details about scuba tank valves, including what they are made of, how they work, different types of valves, single outlet vs. double outlet cylinder valves, manifolds and their use in diving cylinders. We will also see how a regulator is attached to the valve and how the valve connects to the cylinder.
This post is part of a series describing scuba tanks characteristics and features in more detail. If you want to improve your diving knowledge, check out my other post on scuba cylinder markings.
What is a Scuba Tank Valve?
First things first, scuba cylinders valves, or as some people call them, pillar valves are high pressure, manually operated valves connected to the neck of a scuba cylinder. They control the flow of air or breathing gas to and from the pressure vessel and connect to the scuba regulator.
No matter what material your scuba cylinder is made of, valves are usually made of solid brass casting or forging. They’re screwed into the cylinder neck thread and sealed by an o-ring or thread tape. The valve knob or handwheel is a cool knurled or ridged rubber, plastic, or metal fitting attached to the valve spindle. You can use it to rotate the spindle and open or close the valve.
Recent models of scuba tank valves usually use hard rubber or tough plastic. They often incorporate molded grips and a metal insert to engage the square or flatted part of the spindle, which they attach to using a slotted nut.
Scuba tank valves might seem like a small detail in scuba diving, but they’re actually super important to ensure a safe and enjoyable diving experience. So make sure to check your scuba cylinder valve before you hit the water!
How does a Scuba Tank Valve Work?
In its simplest form, a cylinder valve controls the air (or breathing gas) flow from the scuba cylinder and is connected to your regulator via a DIN or Yoke connector. The cylinder valve is operated manually via a handwheel which you should open fully before starting a dive.
Many scuba tank valves have a burst disk, which is a thin copper disk that will break letting gas escape if the tank pressure is too high.
What are the different types of valves on a scuba tank?
The most common types of scuba tank valves are chrome-plated single valves. They may either be K-Valves, J-Valves, or DIN Valves.
K-valves are found in most tanks, particularly in the United States. They are extremely simple and use Yoke attachments for the connection with Yoke compatible regulators. Assembling a regulator with a K-valve is super easy. You simply slip the regulator connector and Yoke regulator attachment on the K-valve and gently tighten the regulator screw against the rear of the valve.
J-valves are similar to K-valves, but they have an embedded reserve mechanism. The J-valve reserve mechanism consists of a spring that shuts down the airflow when your tank pressure drops below 500 psi. J-valves are rather obsolete as they have been substituted by highly reliable pressure gauges and dive computers with integrated alarms.
In case you are using a scuba tank with a J-valve, I strongly recommend deactivating the air reserve mechanism by pulling the rod that’s attached to the reserve lever. Most J-valves use Yoke attachments for the connection with Yoke compatible regulators.
K-Valves and J-Valves mostly use Yoke attachments, particularly in the US. However, some scuba tanks use DIN Valves. This is particularly the case in Europe, or even in the US for technical diving. DIN stands for “Deutsches Institut für Normung”, or “German institute for standardisation”.
DIN valves are commonly used for scuba tanks with service pressures over 3000 psi. Needless to say, most DIN valves use DIN attachments to connect to regulators. You can tell a DIN valve just by looking at it as its hole connection is wider and doesn’t have an O-ring on it. In the case of a DIN valve, the O-ring is located directly in your regulator’s first stage.
How to Convert Din to Yoke valve?
Converting a DIN valve to a yoke valve is a relatively simple process, and with a few tools and a little know-how, you’ll be ready to hit the water in no time.
First things first: make sure you have the right parts. You’ll need a DIN-to-yoke adapter, which is a small metal piece that screws into your DIN valve and provides the necessary threads for a yoke regulator. You’ll also need a wrench or pliers to tighten everything up.
Once you have your adapter, it’s time to get to work. First, remove any dust caps or protective covers from your DIN valve. Then, screw the adapter into the valve as tightly as possible. Use your wrench or pliers to make sure it’s snug – you don’t want any leaks!
Next, attach your yoke regulator to the adapter. This should be a straightforward process – simply slide the regulator onto the adapter and tighten the retaining screw. Also in this case, make sure everything is tight and secure before heading out to the water.
One thing to keep in mind is that converting a DIN valve to a yoke valve may affect the pressure rating of your tank. DIN valves are typically rated for higher pressures than yoke valves, so if you’re converting a high-pressure DIN valve, you may need to have your tank’s pressure rating checked by a professional.
Overall, converting your dive cylinder from a DIN valve to a yoke valve is a quick and easy process that can make all the difference in your scuba diving experience. With the right tools and a little bit of patience, you’ll be able to enjoy your dives with ease and confidence.
If you want to convert your dive cylinder from a Yoke valve cylinder to a DIN one, you will need to do the reverse process and either unscrew the adapter or buy a a clamp style adapter that screws on top of the cylinder valve.
Single Outlet vs. Dual Outlet Scuba Tank Valves
When it comes to scuba tank valves, there are two main types to choose from: single outlet and double outlet. Some divers call double outlet valves “H-Valve“.
A single outlet valve has one opening for a single regulator. This type of valve is commonly used for recreational diving, as it provides a simple setup and is generally more affordable than double outlet valves. However, single outlet valves may not be suitable for technical diving, which requires multiple independent air supply sources in case of an emergency.
Double outlet valves, on the other hand, have two openings that allow for two first stages to be attached. This type of valve is typically used for cold water diving and in some cases for technical diving, where divers need to have two independent air sources. In case one regulator malfunctions or freezes, the diver can switch to the other regulator for a safe ascent to the surface.
When deciding which valve outlet or type of valve to use, it’s important to consider your diving needs and preferences as well as local regulations. Single outlet valves are perfect for recreational diving, while double outlet valves are essential for cold water diving.
In some states in Europe (most of Germany, Austria, Switzerland) double outlet valves are compulsory even in warm months.
Ultimately, the decision of which valve to use should be made with the guidance of a professional or experienced diver.
Note that H-Valves are used on a single dive cylinder. If you are looking at cylinder valves to be used on double cylinders, then you should be looking at dive cylinder manifolds.
Scuba Tank Manifolds
If you’re an avid scuba diver, you’ve probably heard the term “scuba tank manifold” before. But what exactly are they, and why do you need them?
Simply put, a scuba tank manifold is a device that connects two scuba tanks together, allowing you to breathe from both tanks simultaneously. This means you’ll have twice the amount of air available to you, which can be a lifesaver in certain situations. For example, if one tank runs out of air, you can switch to the other tank without having to end your dive early.
Scuba tank manifolds come in various shapes and sizes, but they all serve the same basic purpose. Some manifolds are made for twin tanks, while others can connect more than two tanks together. Some manifolds come with isolation valves, which allow you to shut off one tank if necessary, without affecting the other tank. This is a common standard in technical diving.
When it comes to scuba tank manifolds, safety is always a top priority. It’s essential to ensure that all connections are secure and that the tanks are properly balanced. It’s also important to know how to use the manifold correctly and to practice switching between tanks before heading out on a dive.
Scuba tank manifolds are compulsory for all technical diving courses. They provide an extra level of safety and convenience, allowing you to stay underwater for longer periods of time.
Final thoughts on scuba tank valves
Scuba tank valves are one of the most overlooked elements in scuba diving, yet they are extremely important and allow air or breathing gas to be transferred smoothly from your diving cylinders to your regulator.
If you are diving in the US in warm waters, your tank will most likely have a K-valve with a Yoke connector. If you are diving in Europe or in some exotic locations such as the Maldives, your cylinder will most likely have a DIN Valve with a DIN connector.
If you are diving in cold water, cylinder valves with a double outlet are highly recommended. This allows you to scuba dive with two independent regulators connected to the same tank, and eventually shut down one regulator in case it starts freeflowing.
DIN valves and manifolds are highly recommended (see compulsory) in case you are doing technical diving.
If you want to expand your knowledge on scuba cylinder valves, keep reading the FAQs below.
Scuba tank valves FAQs
Let’s take a look at some of the most frequent questions I receive as a scuba instructor. Note that the answers are valid irrespective of whether you are diving with a steel cylinder or an aluminum one.
Can I reverse a tank and regulator?
One of the common questions I get, particularly from beginner divers, is whether scuba cylinders and regulators can be reversed. The short answer is no, you cannot.
The regulator is designed to be connected to the tank in a specific way, with the first stage of the regulator attached to the tank valve and the second stage attached to the first stage regulator.
Reversing this connection can lead to malfunctioning equipment and potentially dangerous situations underwater. It’s important to always follow the manufacturer’s instructions when assembling and using scuba diving equipment to ensure your safety and the safety of other divers around you.
Can Scuba Tank Valves Freeze?
Yes, scuba tank valves can freeze, especially when diving in cold water conditions. As the temperature drops, the moisture in the air can freeze on the valve, causing it to become stuck or difficult to turn. This can be a serious safety concern, as it can make it difficult or impossible to turn the valve to open or close the tank, which can affect the amount of air available for the diver.
To prevent scuba tank valves from freezing, it’s important to use a regulator with an environmental seal, store tanks in a warm location, and avoid leaving tanks outside in freezing temperatures.
Additionally, it’s important to regularly inspect your equipment and replace any damaged or worn parts to ensure proper functioning.
What is the most common thread form used in scuba cylinders?
The thread form used with most dive cylinders in the US is the 0.750-14 NPSM. It is often referred to as “3/4 NPS.” This thread form is seen on both steel and aluminium cylinders with service pressures of 2400+ (2640), 3000, 3180+ (3498), 3300 and 3442 psi.
What is an M26 valve?
In Europe, an M26 scuba cylinder valve is a type of valve that must be fitted to any new tank that is used with gast mixtures having an oxygen percentage greater than 22%. This is actually a legal requirement following a specific European directive entered into force in August 2008.
An M26 valve is generally compatible with any scuba regulator purchased in teh European Union, designed to be used with gas mixtures with an oxygen percentage greater than 22%.
If you are diving Nitrox in Europe, you will most likely be using a tank with an M26 valve.
