Scuba Equipment Guide: Choosing a Regulator (Part 2)


Welcome back to our Equipment Guide where we help you choose the best suited regulator for you and your type of diving. Here we continue to look at essential regulator features which can differ based on the model, brand, expense, and conditions the regulator will be used in. Once you understand these features and how they relate to the type of diving you are interested, you will hopefully be in a much more confident and happy place to make a decision as to which regulator you should buy. As always the Rowand’s Reef Dive Staff are ready on hand to help answer any specific questions you may have or show you in person some of the best selected regulators we have available in our store. For now we hope that this guide will give you the basic understanding into how regulators work and how to choose the best regulator for you.

(In case you missed it, Click Here to Read Choosing a Regulator: Part 1)

Unbalanced v Balanced v Overbalanced: It’s all about the balance


Both piston and diaphragm first stages can come in either unbalanced, balanced or over-balanced types. These terms refer to the parts used in the first stages and it’s mostly the effect on the springs which is different for each type. Whilst there is a lot of detailed technical background into how each balancing type work, we will focus on giving you a simplified explanation into the workings and then explaining how the effect will relate to you and what the outcome on performance will be in the water.

The Unbalanced First Stage

An unbalanced regulator uses less parts in its design. It essentially has a different pressure on each end of the high-pressure valve, seat and spring assembly and this causes a varying effort to move the spring as conditions change (i.e. change in tank pressure as cylinder becomes depleted or as depth increases). This fluctuating effort transfers through the hose to the second stage. This results in harder breathing effort when using the regulator at deeper depths or at lower tank pressures. This slight sacrifice in performance means that unbalanced regulators are mostly suited for basic diving, however they are often the most affordable and basic regulator models.

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The Balanced Fist Stage

A balanced first stage, whilst using more parts, is much more consistent in how it directs pressure to either side of the valve, seat and spring assembly. This results in a more even effort required to overcome the force of the spring, giving a more consistent (or balanced) delivery of air through the hose to the second stage. This means that the spring assembly is not affected by changes in external conditions (like unbalanced first stages) and will provide a much more consistent breathing effort at all pressures and depths. This improved performance is ideal for a greater range of diving although does come at a slightly increased cost.

The Overbalanced First Stage

An overbalanced first stage gives similar affects to a balanced type but includes a technology that allows the first stage to slowly increase its medium pressure output as ambient pressure increases. This means that it will provide an improving flow of air through to the second stage as you go deeper and the depth increases. This greater relative volume of air theoretically makes breathing easier as you go deeper. However, a slight negative to this overall regulator sensitivity, means that a diver needs to be more aware of potential freeflows, mostly at shallower depths. As such, an overbalanced regulator will often be set up with an inhalation adjuster (see section below) and the diver will start their dive with the second stage slightly detuned to prevent any freeflow, and then alter the adjuster as depth increases to lower the resistance and provide the best performance at the desired depth. The high performance output of overbalanced regulators are suited for specific types of diving, such as deep wreck dives, and are mostly found on the top model regulators available, meaning that they are often the most expensive.

Unbalanced v Balanced Second Stages

As with the first stage, second stages are available in either unbalanced or balanced types, with similar advantages and disadvantages to those for first stages. Much like a first stage a second stage has a valve and a spring, which during a divers inhalation, the effort will open a valve that is then closed by the tension of the spring. An unbalanced second stage will have varying pressure which means it won’t maintain the same performance as depth increases or during low tank pressures. A balanced second stage will provide consistent performance and flow rates at any depth as it routes air to the backside of the valve to help counteract the force of the spring. This results in less effort required to open the valve, making breathing easier under heavier demand (such as increased depth).


So what does all this mean?

Essentially the answer to which option is right for you is dependent on the money you wish to spend and the type of diving you intend to do. Whilst balanced or overbalanced regs will give a better performance overall, it doesn't mean to say that unbalanced regulators are bad, and there are many excellent unbalanced regulators available that excel at entry level recreational diving. The additional parts and precision engineering together with additional manufacturing complexities for balanced and overbalanced regulators will obviously result in a higher cost, yet will perform slightly better for certain types of diving, such as deeper recreation or technical diving. The best solution will be to find a balance(!) between cost and performance that you are happy with and will ensure you are comfortable and confident when using the regulator on dives.

Inhalation Adjuster (also known as Opening Effort Control Knob)


We mentioned the Inhalation Adjuster above in the section about overbalanced regulators. An inhalation Adjuster can be found on most balanced second stages. As seen previously, inside the second stage is a valve and spring assembly. When a diver inhales, the effort opens the valve which releases the air and the spring then closes it. An inhalation adjuster is a small switch which can be used to alter the effort required to open the valve. This is mostly useful for deeper dives where a comfortable inhalation resistance at depth may result in a freeflow at the surface. Adjusting the resistance means there will be less chance of a freeflow in the shallows, and you can still adjust as you descend deeper to maintain a comfortable breathing effort. Whilst not essential to have on a regulator, it is a very useful feature that give the diver a nice simple amount of control over the sensitivity of the regulator and some customization based on the type of diving you are doing.

Venturi Assist System: How to Control the Airflow

Regardless of whether a second stage is balanced or not, it will likely have a way of controlling the flow of air inside the second stage, by enabling or disabling what is known as the venturi effect. Regulator designers can take advantage of the venturi effect to assist with breathing effort and so the Venturi Assist System will allow a diver an easy method to alter the venturi effect and therefore control the ease of breathing in the second stage.


A Little Physics understanding goes a long way…

Simply put, the venturi effect is where the flow of air into the second stage is used to create a vacuum or area of low pressure behind the second stage diaphragm. This is due to fast-moving air particles being forced through the constricted valve area dragging along slow-moving air particles in the region around the airflow. The absence of the slow-moving air particles create the low pressure vacuum behind the diaphragm. When a diver inhales the diaphragm flexes towards him which opens the valve and initiates the airflow. The effect of the vacuum from the venturi effect will then add to the force required to hold the diaphragm towards the diver and allow an easier breathing effort that only requires the slightest inhalation to initiate the airflow. A Venturi-enhanced regulator is very enjoyable and easy to breathe from.

The main downside, however, of a regulator that uses the venturi effect to enhance breathing performance is that they are more susceptible and sensitive to free flow, especially when the regulator is out of the diver’s mouth at the surface. You may have experienced this in the water if you ever take your reg out of your mouth and leave it mouthpiece up. The venturi effect will act to continue the airflow until the diver turns the reg mouthpiece down to stop it. Hence the option for the diver of the Venturi Assist System to control when the Venturi is enabled or disabled on the second stage.

where do you find a Venturi Assist on the regulator?

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Most Venturi Assist Systems will be in the form of a small switch on the side of the second stage. This switch will be labelled with 2 options. Depending on the brand and model of reg these options will be: +/ - or Dive/Pre-dive or On/Off. This switch allows the diver to control the venturi effect by setting it to +, Dive or On to achieve maximum venturi assistance for easier breathing during the dive or setting it to -, Pre-Dive or Off to prevent the second stage from free-flowing during entry or while swimming on the surface. (Note that disabling the venturi-enhanced breaching does not stop the regulator from giving you air but it will increase the resistance and make it slightly harder to breathe from until you switch the venturi assist back on)

So Is It Worth it?

Ultimately when it comes to choosing a regulator, picking one with a venturi assist system will give you a nice amount of control over the airflow that will make your breathing effort much more comfortable and easy. Regulators with Venturi-enhanced performance are a pleasure to breathe from and is something that we would highly recommend. Most modern regulators will have some form of venturi assist system built in meaning that the technology is not just limited to high end expensive models. A lot of basic, entry-level regs will have this feature giving you a lot of options to pick from!

The Alternate Second Stage (no the other type of Octopus!)


All regulators need to have an alternate second stage, known as an octopus. This is obviously an important safety feature as it acts as a backup for you and your buddy should one of you need to breathe off the other person’s air supply. When it comes to buying an octopus, you have a choice of buying one that matches the model of your primary second stage (but still comes in the high visibility yellow color) or a different lower performing but often slightly cheaper model. Whilst it is nice to have a matching set, a different model octopus will work and perform its job just fine and as such is a good way to save some money when buying a regulator set. Also keep a look out for reversible octopus. These are second stages that can be used and breathed from both the right way up and also upside down. This potentially helps in an out-of-air situation where your buddy may be panicked and may forget which way to put the octopus mouthpiece in to breathe from. Certainly a useful feature to have in an alternate second stage octopus.

Regulator Servicing & Maintenance:
it’s your safety at the end of the day!

In general, regulators should be serviced every year by a trained technician. Considering your life depends on the regulator providing a steady supply of air to keep you alive underwater, missing maintenance and risking the possibility of regulator failure is something you seriously do not want to do. As such when it comes to purchasing a regulator, servicing and maintenance is something important to consider. There are 3 main considerations to make with regard to servicing:



Obviously there is a cost involved in servicing a regulator. Similar to having your car serviced there will be a cost for labour and a cost for the parts that may be required or need to be replaced. Whilst the labour cost should be pretty standard, the cost of parts can differ quite significantly based on model and brand of regulator. However, there are a few brands, most notably Aqua Lung and Apeks Regulators, that offer a scheme called ‘Free parts for Life’. This program essentially states that the cost of any standard service parts will be free and covered providing you service your regulator regularly (every year). As such, this type of program is a real benefit and big cost saver in the long term - something which is important to bear in mind and which we highly recommend when buying a new regulator.

Ease of service

As there are lots of regulator brands and models available, it is important to make sure that the regulator you pick is able to be serviced at a local dive shop. Some more specific models or brands may be more complex and technically difficult to service and as such you may have a harder time finding a technician trained to service your reg. When buying a reg, make sure that you can find someone near you who is trained and able to service the type of regulator you have.


Availability of parts worldwide

Similar to ease of service above, some regulator brands will have more presence in some countries worldwide than others. As such it may be difficult to obtain specific service parts for your regulator in certain parts of the world. This increased difficulty can sometimes lead to increased costs when it comes to servicing. Sticking to common and popular brands will ensure a higher chance of worldwide availability of parts. Otherwise try to make sure that the location you intend to dive and use the regulator has dive shops that are able to obtain parts from the brand you use.

Other final considerations: it’s all in the details



When it comes to hoses there are two main choices to consider when buying a regulator set. Firstly, that the length of the hoses are comfortable when using the regulator. You want to make sure the hose is not too short that it pulls you back when you turn your head. This is especially true of your octopus hoses which benefit from a longer length if you ever need to swim with your buddy breathing off your octo. Secondly, there are two main types of material used in hose construction: traditional rubber and newer braided. The traditional rubber works just fine and has been an industry standard for years. However the newer braided hoses are more lightweight and flexible than rubber hoses and tend to last longer and not wear out as quickly as rubber hoses can do. They are slightly more costly than rubber hoses but usually worth the extra cost. 

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Nitrox usage

If you want to use your regulator with enriched air nitrox, you need to make sure that the regulator is prepared and set up to safely use the specific percentage of nitrox you are diving with. Most regulators are manufactured and set up out of the box to be compatible with increased oxygen content up to 40% Enriched Air Nitrox. If you intend to use your regulator with a nitrox mix above this, some regulators are manufactured as nitrox versions which are compatible with 100% straight oxygen otherwise you will need to send your regulator off for oxygen cleaning.



Being comfortable in the water is very important and can have a big impact on your air consumption. The mouthpiece is what attaches the regulator to you and so having a good mouthpiece is a simple but really important thing on a long dive. There is nothing worse than having jaw fatigue or being sore from a mouthpiece that doesn’t fit properly. Most mouthpieces are made from silicone and come in different styles. The basic/standard mouthpiece has two plain ordinary tabs to bite down on and can sometimes be difficult to keep in place without biting quite hard. They are often found on rental equipment or basic entry level regs as they are very cheap and simple to replace and they fit almost everyone. Moldable mouthpieces can be heated in water and then fit inside your mouth where they will mould to fit your mouth and bite profile. They are very comfortable as they give a custom fit but tend to be slightly more expensive. Finally there is the comfo-mouthpiece. These designs help lock the mouthpiece in place which is especially good if you turn your head a lot. They will have bridges to connect the tabs together and winged sides ensure a comfortable grip and fit without having to bite significantly hard. They fit most everyone and it is very difficult to go back to a basic mouthpiece after diving a comfort mouthpiece - Well worth the extra few dollars!


Exhaust Tees

Have you ever had issues with bubbles in your face? When you exhale underwater the air is expelled out of the regulator second stage through 2 exhaust tees. The purpose of these tees are to try and direct the bubbles away from your face and field of vision. Some regulators are better than this than others however, and some regulator models have the option of switching out different shape exhaust tees which are designed for different uses. For example, a wider exhaust tee allows for minimal bubble interference (essential for underwater photography) whilst a narrow exhaust tee gives a smaller compact and travel-friendly regulator. Ultimately this feature may not be super important for you, but it is a nice addition if you like added customization for your regulator.

The Bottom Line


There you have it! If you made it through the guide then hopefully you now have a good knowledge and understanding of how regulators work and what features to look for when choosing or looking to purchase a regulator. Remember, take your time to choose and continue to do your research so that you are happy and confident when it comes to buying and using your new regulator on dives - after all it’s a very important piece of dive equipment! We hope we have provided some useful advice into what to look for when browsing the different regulator models and also how to decide what features are important for you and the type of diving you intend to use the regulator for. Whilst it is nice to try and save some money when buying a regulator, remember that this piece of equipment will likely be with you for at least a few years so don’t be afraid to buy something you know is of good quality and will keep up with you as you evolve and develop your diving ability in the future. 


As always, our dedicated Dive Staff here at Rowand’s Reef are ready and able to answer any regulator-related questions you may have. You can come visit us instore and view the regulators and features we have talked about in this guide up close or you can even rent some of our high quality rental regulators, the Apeks XL4, and take them out for a test dive to experience some of the features first hand. Thank you for taking the time to read our Choosing a Regulator Guide and we hope you enjoy shopping for and diving with your new regulator!