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A guide to regulator servicing in 8 steps

Posted by Pia Limpiyasrisakul on

In this tech article we will go over the steps we follow from the moment a customer brings in a regulator set in our shop until the regulator set is picked up or returned to the customer. As we describe this sequential procedure, we will give you plenty of tips & tricks to make your service work more efficient.

This step by step guide is aimed at novice pro-technician but also suitable for, and can be easily adapted by DIY service technicians at home. We’re sure even the seasoned pro might find a few tips worth considering.

Why work with a procedure? A well thought of procedure will guide the technician through the process in a logical sequence and prevent the technician from omitting crucial steps, therefore making the process streamlined and efficient and ‘watertight’.

Our step by step procedure has 8 major steps:

    1. Book in the customers’ equipment
    2. Pre-servicing test and inspection
    3. Disassembly of the equipment
    4. Cleaning procedure
    5. Inspection
    6. Re-assembly of the equipment
    7. Set- up and adjustment of the equipment
    8. Quality control and return the equipment to the custome

In this article we focus on the procedure for ‘air use’. If parts are to be oxygen cleaned, the same steps and procedures can be used but additional procedures and techniques will have to be added to step 4 to 8. The details of these procedures and techniques are outside the scope of this article.

Prior to any service work or attempts we strongly recommend getting professional training in regulator servicing of the particular brand you intend to work on or have the work done by a qualified and trained technician.

Step 1: Book in the customers’ equipment.

When a customer brings equipment into your shop, it’s good practice to give the customer a receipt that positively identifies the equipment he has delivered to your shop for service. At the same time, this receipt can be used to make the customer sign for receipt of the equipment to be returned once the service has been completed (step 8).

What should be included into the booking form?

  • Name and contact details of the customer
  • Date due
  • A job number
  • Description of the equipment handed over together with the serial numbers
  • Type of service required (air or oxygen service)
  • Your terms and conditions of the service to which the customers agrees by signing the form

Tips & tricks:

If any obvious and significant defects are spotted, note this down on the booking form to avoid discussions in the long run. Examples: regulator delivered in bits and pieces, a second stage case cover missing…

  • Ask your customer as well if there is anything wrong with the equipment or if the equipment is not functioning properly. Examples: second stage breathes wet, difficult to inhale, second stage free-flows, the set is leaking from the hose…
  • If a customer brings in a mismatched regulator set – aka the ‘Frankenstein’ regulator - (example: Scubapro first stage with Mares octopus), point this out to the customer and explain the possible dangers of this combo and why you won’t be able to assemble the set as presented. In the example mentioned, this doesn’t mean you cannot service the Mares octopus, it means you won’t be reconnecting it to the first stage again. This mismatching not only applies to different brands but also within the same brand: often only certain combinations are sanctioned. A good example of this would be the Poseidon brand. Non-matching brands or wrong combinations within a brand are simply a no-go as they could lead to potential dangerous situations, equipment failures or malfunctions and could cause bodily harm to the user (or worse).  As a pro technician, ignoring this could get you into hot mess if anything goes wrong (liability issues).
  • Try to make the ‘booking process’ a smooth process, nobody wants to spend 30 minutes in your shop just to get a piece of paper.

Once the customer has left the premise, we usually continue the booking process by 1/ completing the worksheet (*) and 2/ putting the worksheet together with the regulator in a suitable plastic container. The container, worksheet and regulator are now paired during all the following steps. The reasoning behind this is to keep a set together and avoiding the mix up of parts between different sets of the same customer or worse between several customers.

We also like to use 2 racks to segregate uncompleted and completed work. As long as the work is not completed, the work returns to the ‘work in progress rack’ after each step. Only when step 8 is completed, the work goes to the ‘completed rack’. This system should help you avoiding that uncompleted work accidentally gets returned to a customer.

(*) A worksheet or job sheet is a form that will assist the technician during the actual service. Apart from the same basic details on the booking form (customer details, serial number, job number…) it also allows the technician to collect and record service notes, test results, parts used, hose orientation…

Step 2: Pre-servicing test and inspection.

We like to start this stage of the service by recording on our worksheet the hose orientation of the set, so once the service is completed it can be assembled just as the customer gave it to you. With the abundance of smart phone use, a clear picture achieves the same result.

Next would be to put the equipment on a preliminary test to ascertain the ‘health state’ of the equipment.  We consider this a pretty important step as it will give you the ‘base vital signs’ of the equipment that will assist you to solve possible problems later on or allow you to pay special attention to certain aspect/components.  It’s a bit along the lines of preventions is better than the cure. Some examples:

  • A high intermediate pressure could be due to: a faulty setting or adjustment, a minor flaw in the soft/hard seat combo…
  • A free flow of the second stage could be due to: a faulty setting of the second stage lever height, intermediate pressure being too high, intermediate pressure creep, a flaw in the orifice/poppet combo…

The preliminary testing should be carried out with full supply pressure (i.e. a full cylinder or and adjustable air supply set at 200 bar / 3000 psi).

If you feel the urge, you can also perform these tests at low supply pressure (around 35 bar / 500 psi) to get a complete feel for the set and to see if the regulator follows the expected pattern for the specific type of regulator. Example: if you have an unbalance piston first stage, at low supply pressure, you should see the intermediate pressure drop and the cracking effort of the second stages increase. Testing at low pressure can be achieved by connecting the regulator set to a cylinder with low air pressure or using an adjustable bench air supply.

Hold on a minute, as you’re likely unfamiliar with the equipment, time for some personal safety measures (i.e. PPE time): safety glasses and your personal mouthpiece to measure the cracking effort are strongly recommended.

The parameters to be checked and recorded on your worksheet are:

  • Intermediate pressure(*): does the reading ‘lock-up’ or is there any drift (positive or negative) or creep?
  • Cracking effort (**) of the primary second stage.
  • Cracking effort of the secondary second stage (octopus).
  • Intermediate pressure under full purge – this gives indication of the possible flow restrictions (example: blocked filter, cylinder valve not fully open) -.

If you’re looking for some advice on test equipment, you might find this article a worthwhile read: ‘Instrumentation options? Choosing the instrumentation that is suitable for you.

Once you have recorded the parameters, you have to evaluate your findings; otherwise this exercise would be pretty futile. This means you have to compare the recorded values with the manufacturers recommended values and make some conclusions. These conclusions will help you focus on or target specific areas of the regulator during the next steps of the service. You got to get your mind-set into forward thinking and anticipating problems before they actually occur.

Example: you encounter a slight free-flow of the second stage and measure an intermediate pressure of 11.5 bar and the manufacturer’s recommendation is 8.5 bar. Obviously the intermediate pressure is too high. Start thinking ahead of the game: why is the intermediate pressure too high? Think of some causes, i.e. wrong setting, worn soft seat, weak spring, too much shims, damaged hard seat…  Furthermore, it would be entirely plausible that the slight-free flow could be induced by the excessive intermediate pressure… Other causes like i.e. lever set too high, a flaw in the orifice/poppet combo, weak spring… could also trigger the free-flow.

Tips & tricks:

  • If you encounter issues during your testing you can go about those as follows:
    • Small problem or issue: apply quick fix if possible and continue evaluating. Examples: HP hose leaking – disconnect the pressure gauge/console and block the port with a port plug -, leaking port plug – tighten the port plug-.
    • Large problem or issue: leave as is (don’t try to fix or adjust the problem) and move on to consecutive steps – you are likely not able to get a full set of readings -. Examples: major leaks, free flowing, uncontrollable intermediate pressure creep.
  • Complete your test in a logical sequence especially if you decide to test at both low and high pressure. Start for instance at low pressure: measure the IP and cracking effort of the primary seconds stage and octopus; then go to high pressure and measure the cracking effort of the octopus, the primary second stage and the intermediate pressure. A logical sequence avoids you to go back and forward and lose valuable time.
  • Check moving parts of the second stage regulator(s) under pressure especially if they have venturi or diver adjustable inhalation effort adjustment options. Sometimes they will be seized (not moving) or turned to maximum positions. If then you turn them to the minimum position, often the second stage free-flows.
  • For those having a calibrated supply pressure gauge in their setup, this is a good time as well to compare the reading of the customer’s pressure gauge with your calibrated gauge to see if the customer’s gauge is working properly. According to EN250, the accuracy should be within +/- 15 bar at 300 bar, +/- 10 bar at 200 bar, +/- 10 bar at 100 bar and +/- 5 bar at 50 bar. If the reading is outside the specifications, the gauge should be replaced.

(*) See our article: "Measuring intermediate pressure".

(**) See our article: “Measuring cracking effort”.

Step 3: Disassembly of the equipment.

Before taking the regulator apart, a couple of reminders:

  • Ensure the system is depressurized and disconnected from the air supply.
  • Have the most recent manufacturer’s exploded drawing in front of you.
  • Have the most recent manufacturer’s service manual available for reference and guidance.
  • Have appropriate standard and specialized tools available in order to minimize the risk of damage to the equipment and to facilitate the job.

We like to start this process with splitting the regulator set up in separate entities (stages) and disconnect all the hoses. As we disconnect the hoses, for efficiency sake, we would do a thorough inspection of all of the hoses and its threaded fittings. Damaged hoses or hoses with signs of wear and tear should be set aside and replaced. Also pay attention to what type of hoses are being used; ideally they should be original manufacturer’s hoses. The use of different brand or non-original hoses could affect the performance of the regulator. Example: a smaller bore hose could limit the maximum possible flow rate through the second stage. Also pay attention to non-original mouthpieces: as long as they do not obstruct the housing shank (air passage from mouthpiece to housing) and fit nicely around the shank (i.e. not loose), we consider it acceptable.

As the first stage, second stage, octopus and pressure gauge assemblies are separated we would place those in smaller boxes to keep the items separated and not to mix up parts – the latter can easily occur between primary and secondary second stages -.

If during the disassembly of the individual stages, you encounter issues due to seized parts, we recommend you to have a look at our article dealing with “Seized parts, damaged parts and broken tools” for some advice.

It often pays off to loosen parts before totally unscrewing them as larger assemblies are often easier to hold and it also avoids having to go back and forward. A good example of this would be a diaphragm first stage: with a vise handle in the regulator and the assembly secured in a vise, loosen the environmental cap, diaphragm ring and the yoke or din connector. Then remove the assembly from the vise, remove the vise handle and unscrew all those parts by hand on the bench.

Regardless of your experience, it is wise to have the drawing in front of you and lay the parts out on the bench just like in the drawing as you disassemble them. That way you can check and ensure all components are there and none of them are missing. It is not uncommon to have missing part(s) in an assembly.

Once the regulator is totally disassembled, we would set apart all the parts that would have to be replaced by the manufacturer’s recommendations – no need to clean parts which are to be discarded -. Some examples of those parts are: O-rings, filter, soft seats, star washers, diaphragms… Please note that this will strongly vary per manufacturer.

Tips & tricks:

  • If during your disassembly you come across any parts that are damaged, set them aside and order a spare one if required. On our worksheet we have a section where we can record all the parts and kits used during the service. Record this as you go, so you can charge your customer accordingly.
  • We generally check parts for defects as they are being disassembled. Generally speaking you inspect the parts thoroughly after cleaning; however, early detection of defects might put you in an advantageous position as you could order those parts earlier.
  • If during the disassembly you note any anomalies, defects… record this on your worksheet.
  • When inspecting the hoses, don’t forget to pull away the hose protectors to check underneath.
  • We like to keep delicate parts like orifices, hard seats and knife-edge pistons in separate containers (like the old film canisters) to prevent damaging them during handling.
  • Take note of setting positions as this can facilitate the set-up – get you back in the ball-park -. Examples: what’s the orifice depth of the second stage, what the relation of the second stage lever to the casing, what’s the height/depth of the adjustment screw in the diaphragm retainer of a diaphragm first stage, how many shims are installed…
  • When holding first stages with a vise handle (tommy bar), screw the tool into the high pressure port as this port is the strongest. Do not use low pressure ports on swivel caps.
  • We like to disassemble the stages on a neoprene service mat. It helps protecting the parts but more importantly it helps in ‘catching’ parts and prevents them from rolling of the workbench.
  • When removing circlips, we recommend using safety glasses as there’s a chance they ‘fly off into space’ due to springs that tension them up underneath.
  • As you disassemble the gear, keep a keen eye out for sign of tampering.
  • Said the above about tampering, bear in mind that it’s always possible that the wrong parts have been installed (this often happens with spring and diaphragms). This is extremely difficult to detect, either you know because you’re so familiar with the parts or you really struggle to adjust the regulator or you do a bunch of the same regulators and you spot an odd part out. How do you know for sure? You don’t unless you compare the suspect part with a known good original part. This is one of the reasons why we are so specific about keeping all the parts of a specific stage together in a box.

Step 4: Cleaning procedure.

There are many ways to get ALL the parts (including hose ends) cleaned but our favourite is still the use of an ultrasonic cleaner as it’s quick and highly efficient. The goal of the cleaning procedure is to remove corrosion, dirt, salt deposits and grease residues.

If parts are extremely soiled – example: a slimy inside of second stage housings - or greasy – example: spring of environmentally packed regulators -, give them a preliminary scrub with hot soapy water and a stiff brush.

We like to start off with giving the parts an ultrasonic soak in hot soapy water for about 5 to 10 minutes followed by a rinse with hot water. This first bath will take care of gross contaminants and greases. We then soak them another 5-10 minutes in a hot ultrasonic ‘acid’ bath, follow by a good rinse in hot water and a thorough drying regime.  For the drying process we prefer to ‘towel’ the parts first with a microfiber cloth followed by blasting them with clean air using and air gun.

Tips & tricks:

  • Recommended cleaning procedures and cleaning agents greatly vary from brand to brand and are described in the service manuals. We recommend following them!
  • As a general rule of thumb, only metal parts are given and ‘acid’ bath. We recommend adjusting the time in the ultrasonic cleaner according to the state of the regulator. Example: if the regulator metal parts look like brand new out of the box with no signs of corrosion, a few minutes as opposed to 5-10 minutes in the ultrasonic cleaner will do.
  • Small parts have tendency to fall through the mesh of the ultrasonic cleaner basket. We really enjoy the use of tea-eggs to keeps those tiny components together in the bath.
  • When rinsing tiny parts or draining liquids that contain tiny parts, it’s never a bad idea to do this over a strainer in the sink - good luck trying to recover a small part from a sink drain, it will be down the drain -.
  • Take care not to damage delicate parts like hard seats, orifices or knife edge pistons in the cleaning process. Again, tea-eggs will help you protect and separate those components from the other items.
  • A few do’s and don’ts for ultrasonic cleaners:
    • Never place items directly on the bottom of the cleaner, always use a basket.
    • The efficiency of cleaning will be reduced if the basket is overloaded.
    • Ultrasonic waves cannot travel through plastic containers. So if you wish to use containers with different solutions in an ultrasonic cleaner filled with water (carrier bath), use glass containers.
    • If you use a carrier bath, put a couple of drops of dishwashing soap in the water (carrier) to help break the surface tension.

Step 5: Inspection.

Inspection of ALL the parts is a critical step. Missed out defects will come back to haunt you later – most likely during the set-up and testing phase –. Even worse: those defects will leave your shop undetected if not all checks are performed. The basic rule: all parts that are damaged or defective are to be replaced; it’s as simple as that. Of course common sense plays a role as well: an external scratch in the chroming of a fist stage body doesn’t mean you have to replace the body.

Apart from the ‘naked eye’ and proper illumination, we recommend the use of magnification: a magnifying glass, jeweller’s eyepiece or stereo-microscope is suitable means for this purpose (x3 to x10 will do).

During the inspection of all parts, you will be looking for: 

  • In general: damages, deformities and wear and tear on all parts.
  • Damages to the sealing surfaces such as the first stage hard seat and second stage orifices. This also applies to the soft seats if they are to be re-used.
  • Scratches on O-ring glands and O-ring sealing surfaces (examples: edge of flow through piston, hard seats, orifices, balance chambers…).
  • Burrs on parts.
  • Flaking of the chrome layer on parts (especially important on internal parts and internal sealing surfaces as ‘loose flakes’ could become dislodged and interfere with the proper operation of the regulator).
  • Holed, torn, perished or deformed diaphragms. This for first stage diaphragms if they are to be re-used as for second stage inhale and exhaust diaphragms.
  • Cracked and deformed springs.
  • Damaged or cracked threads.
  • Cracking, fraying or perishing of O-rings if they are to be re-used.
  • Bent parts, especially levers.
  • Second stage balanced poppets should be straight and the feet that engage with the lever should not be damaged.
  • For exhaust diaphragms: pay particular attention to she skirt (edge) as this is the sealing edge, if should not be damaged. Furthermore, make sure the barb (lip that holds the exhaust diaphragm in place in the second stage housing) is intact.
  • Damage to the hoses if you haven’t done so in step 3.
  • Finally don’t forget to carefully inspect the mouthpieces as well especially for torn bite tabs and punctures.

Tips & tricks: 

  • Burrs and scratches on sealing surfaces (e.g. first stage hard seat, tip of a flow through piston, second stage orifice) are easily detected by running your fingernail over the surface or edge.
  • Flexible parts can easily be inspected for holes by gently stretching them out against a light source. If you see the light shine through, the part is holed. Minor holes and tears are often not spotted if the flexible part (i.e. diaphragm) is in a relaxed state.
  • Springs can be checked by having them stand upright on a flat surface and check them for square by using a ruler against their side and also across the top. It is now easy to visually see any misalignment or both in the horizontal as vertical plane. If springs are bent or deformed, they should be replaced. You can also roll them over a flat surface, they should roll straight.
  • Cracks in casings or housings are difficult to spot. Furthermore, once the tension is out of the housing, the cracks often tend to disappear and avoid detection. Therefore we always have a close look at the casing prior to removing the second stage hoses and the barrel of balanced second stages or the valve body of unbalanced second stages. Cracks in the housings are common and most often caused by over tightening parts and or hoses.
  • We like to ‘polish’ the seating surfaces of all hard seats – also non-removable hard seat in first stage bodies -, knife-edge pistons and orifices with an eraser (the ones on the back of a pencil are great for this purpose). After polishing them, do not forget to blow away the ‘eraser fluff’.
  • New parts that will be installed also should be inspected using the same criteria as described above.
  • Any defects found should be written down on your worksheet.

Step 6: Re-assembly.

Prior to reassembly, a couple of reminders:

  • Have the most recent manufacturer’s exploded drawing in front of you.
  • Have the most recent manufacturer’s service manual available for reference and guidance.
  • Have appropriate standard and specialized tools available in order to minimize the risk of damage to the equipment and to facilitate the job.
  • Have the manufacturer’s recommended greases available.
  • Only use original manufacturer’s parts for the so called ‘service kits’ and other replacement parts of required. The use of non-original parts could affect the regulator’s performance, not to mention potential liability issues in case something goes south later down the line.

Often service kits are suitable for several models within the same brand and might contain too many O-rings. Therefore, with the use of the provided O-ring identification chart, select the correct O-rings and quantities required. Put aside the ones you don’t need.

Not all brands include all the required parts in their service kits. Example: Mares first stage kits contain all the required O-rings and filter however lack the diaphragm and poppet as this has only to be replaced every other year. These have to be ordered separately.  For other brands, only dynamic O-rings are included and static O-rings are to be re-used if they pass the inspection, example Oceanic.

To make sure you will not forget to assemble anything, lay all the parts out on your workstation just like in the drawing.

O-rings are to be lubricated with the manufacturer’s recommended grease. A tiny dab of grease on the fingers is sufficient to lubricate all O-rings.  Work the grease all around the O-ring(s) and once completed they should be shiny but not dripping with grease (i.o.w.: no excess lube should be visible).

Use a torque wrench to tighten parts where a torque value is recommended by the manufacturer.

We like to rebuild all the stages first before starting to reassemble the set. It pays off to think a little ahead of time to avoid having to do the same job over again or having to disassemble components again. What we really refer to is how the stages have to be set up in the next step. Examples:

  • For a balanced diaphragm first stage with an environmental seal: don’t install the load transmitter, environmental seal and retainer cap yet, as these components would have to be removed again to adjust the intermediate pressure.
  • For many Aqualung second stages, the lever height is set under pressure with a special tool whilst the diaphragm is not installed. If you would install the diaphragm assembly at this stage, you will have to remove it once more.
  • Don’t install and cable tie mouthpieces yet as you still have to measure the cracking effort using a specialized mouthpiece.
  • Don’t install case pins on second stages yet, just in case there is a problem during setup and they have to be removed. This is for instance applicable for Mares, Scubapro.

There are 2 valuable tests you can perform during this step and we like to share with you as those have saved our butts many times over. Therefore we always perform them (if applicable) and really recommend you to do the same. There are perfectly suitable for the tips & tricks section but they deserve a little more attention.

Test 1: balance chamber test for balanced second stages. With a new O-ring and soft seat installed on the poppet, close of the air passage in the soft seat with a finger. Now without the spring, push the balance chamber over the poppet stem. If there are no leaks, the air inside is being compressed. If you now release the balance chamber, the compressed air should push the balance chamber backwards again. If this doesn’t happen try again – it’s always possible you didn’t seal the soft seat well -. If this test fails, it means there’s a leak in the poppet – balance chamber assembly and this should be rectified. Possible causes to name a few: scratches inside the balance chamber or on the O-ring gland of the poppet, defective O-ring, cracked balance chamber.

Test 2: watertight integrity component failure test for ALL second stages. Your primary goal with this test is to establish if the diaphragm and exhaust valve are properly seated. It will take a little practise to master this test. To perform the test: on a completely rebuild second stage, close the inlet fitting off with your finger – the location where the hose connects –and create a vacuum inside the second stage and hold the vacuum steady for a few seconds. To create the vacuum you make a firm inhalation (take a good breath in, but not too deep – if you really inhale too forceful, you can pull the exhaust valve through the exhaust spider -).  If the vacuum is steady, the second stage passes the test. If you lose the vacuum there is an issue.  So if this test fails, you can be sure that one of the following will be the case:

  • Diaphragm not properly seated.
  • Puncture in the diaphragm.
  • Exhaust valve not properly seated.
  • Puncture in the exhaust valve or exhaust valve worn out so the edges no longer seal properly (replace the exhaust valve with a new one and if the problem was caused by the exhaust valve, the problem will disappear).
  • Problem with the sealing surfaces of the exhaust spider in the housing.
  • Crack in the housing, very often near the inlet fitting.

Tips & tricks:

  • Once we have selected all the required O-rings, we like to lubricate them all in one go.
  • When reassembling balanced diaphragm first stages we like to start with the spring side first so that the soft seat (poppet) is pushed away from the hard seat once assembling the balance chamber side.
  • To facilitate the removal of threaded parts in the future we like to put a tiny smear on metal to metal threaded connections. Example: first stage diaphragm retainer, first stage spring retainer caps… However not all manufacturers do endorse this.
  • Once you have completely assembled a stage, check you workstation to see if you got any parts left.
  • It often helps speed up the entire reassembly by making smaller sub-assemblies first and then put them all together. Example: assemble poppet and balance chamber combo, assemble the adjustment knob components. Install the poppet / balance chamber assembly into the barrel. Once the complete barrel is assembled, install that into the second stage housing.
  • Keep all the components which are not installed because of the fact that they would have to be removed once more for setting up together in the same box as the stage.
  • Also hoses are to be fitted with new O-rings. The same applies to the ones on the spool inside the high-pressure hose that connects to the pressure gauge.
  • If during step 3 you took note of some settings (example: the relative position of the lever to the second stage casing), you can use this to your advantage to assemble the parts in the same way / same position and get the settings in the ‘ball-park’.
  • Just like in the disassembly phase we personally like to organize ourselves and avoid going back and forward in the process and take advantage that larger assemblies are easier to handle. An example to illustrate this principle: for a first stage we would install all the components and tighten them by hand on the workbench. Once all is installed we would install the vise handle in the HP port and move to the vise to torque or tighten all components like: yoke nut or DIN assembly, diaphragm retainer and the balance chamber.
  • Record what you did and which parts are replaced on your worksheet. Example: ‘First stage disassembled, cleaned, inspected and service kit installed. Spring was found bent -> replaced.’

Step 7: Set- up and adjustment of the equipment.

With the reassembly of the stages is completed it’s time to reassemble the set by using your schematic or picture taken in step 2 to make sure you connect the hoses identically to the configuration as received. Before connecting the hoses to the second stages, put an in- line adjustment tool in-between.

As the stages have been rebuilt, there’s always a change you might have made a mistake. Therefore, before pressurising any rebuild equipment, use the appropriate PPE: safety glasses. We also recommend having a safety valve connected to the intermediate pressure gauge.

For set-up and adjustment procedures, the manufacturer’s guidelines should be followed. An adjustment method suitable for one brand might give you faulty results if the same method is applied to a different brand.  This cannot be stressed enough: set-up procedures are brand and model specific.

Make sure that your final settings and test result are within the given specifications. There is no universal figure/value for intermediate pressure or cracking effort, each model is unique. Some general guidelines and principles on how to adjust downstream second stages can be found in the following article: ‘Adjusting downstream second stages’.

We believe the most important aspect of the set-up and adjustment procedure is cycling the regulator. You can compare this to the ‘running in period’ of a new car. What needs to happen is for the soft and hard seat to adjust to each other and form a ‘mating groove’.  Once this mating groove / impression is established, soft and hard seat will seal airtight and final adjustments can be made. We do not think that a couple of purges will take care of the problem, therefore we really believe in the use of automatic cycling machines available on the market. Many shops and DIY service techs will not have this option at their disposition so manually cycling the regulators will be the only option.

If cycling is your only option we suggest the following ‘generic procedure’:

  • STEP A: connect the regulator set to a low pressure air supply (500 psi / 35-50 bar) and gently open the cylinder valve. Keep an eye on the intermediate pressure gauge to make sure, the intermediate pressure doesn’t shoot through the roof. If this would be apparent, shut the air supply off and correct the problem. If the intermediate pressure is in the ball-park, all is good, if not, make a small adjustment. If the second stage free-flows, get rid of the free-flow with the in-line adjustment tool. If there’s no leak, find the leak position with the inline adjustment tool and then just get rid of the leak.
  • STEP B: gently give the second stages a little purge. Shut the air supply off and depressurize the regulator set. Turn the valve back on to pressurize the set, give a small purge on both second stages and repeat this cycle about 10 times.
  • STEP C: connect the regulator set to a high pressure air supply (3000 psi / 200 bar) and gently open the cylinder valve. Keep an eye on the intermediate pressure gauge to make sure, the intermediate pressure doesn’t shoot through the roof. If this would be apparent, shut the valve air supply of and correct the problem. If the intermediate pressure is in the ball-park, all is good, if not, make a small adjustment. If the second stage free-flows, get rid of the free-flow with the in-line adjustment tool. If there’s no leak, find the leak position with the inline adjustment tool and then just get rid of the leak.
  • STEP D: now gently give the second stages a little purge. Shut the air supply off and depressurize the regulator set. Turn the valve back on to pressurize the set, give a small purge on both second stages and repeat this cycle about 10 times.
  • STEP E: after this cycling period, adjust the regulator using the manufacturer’s recommended techniques to the recommended settings. Now you are ready for you final testing.

Failure to properly cycle a regulator set, is a common reason why regulators develop a slight free-flow after the first couple of dives and need to be ‘re-tuned’.

After the final tuning, with full supply pressure (200 bar / 3000 psi) the following final tests we consider essential: 

  • Verification of intermediate pressure.
  • Verification of cracking effort of primary second stage.
  • Verification of cracking effort of secondary second stage (octopus).
  • Verification of the intermediate pressure under full purge.
  • Leak test.

The following test we consider optional unless specified by the manufacturer and a flow bench is available: flow test.

Whenever you encounter problems and it’s time to troubleshoot, bear the following in mind:

  • Use the KISS principle and consider the most obvious/likely causes first. For those living in Thailand: what is the most likely cause of death? A traffic accident, getting bitten by a cobra snake or loose an epic battle with a polar bear on the street? The polar bear story is not only cool and possible, but highly unlikely, more like a one in a million chance. The chances of meeting your match in a traffic accident are just much higher.
  • Work in a logical order to eliminate the possible causes of the problems, starting with the most obvious ones first.

Once the stages are properly set-up and your findings are recorded, it’s time to depressurise the equipment and to disconnect the in-line adjustment tools. With this completed, connect the first stages to hoses and please don’t forget to use 2 spanners to tighten them up; sometimes a torque value is to be observed. Finally install the remaining components like mouthpieces, case pins…

You’re nearly there; there is one more important test to complete: the leak test. To perform this test, we like to connect the whole set to a small cylinder and submerge the whole assembly under pressure in a tub of water. Give it all a good shake to get rid of air in voids or clinging to hoses. Let the assembly sit for about one minute and then check for trails of air bubbles. If a trail of bubbles is visible, it means there’s a leak and this has to be corrected.

Tips & tricks: 

  • Your final test results should be recorded on your worksheet.
  • Basic principle: adjustments to the second stage will only be effective if the first stage intermediate pressure is stable and correctly adjusted. If you can’t control and adjust the intermediate pressure within the requirements do not move on to the second stages.
  • Generally speaking, some rule of thumbs are applicable – which of course means that there will be some exceptions to those rules -:
    • Diaphragm first stages are adjusted under pressure.
    • Piston first stages adjusted with the pressure turned off (regulator depressurized).
    • Second stage adjustment depends on manufacturer (different procedures), the use of gauges – lever height setting tools - might be required, however the goal is to set the regulator for:
      • Maximum lever height – flow related -
      • Minimum spring tension – cracking effort related -
    • Environmental seals are put on under pressure.
    • Cracking effort is normally set-up with the diver adjustable inhalation effort knob in the minimum position. This means that once the cracking effort is tuned, the diver only can increase the cracking effort to match the diving conditions.
    • When adjusting, make a small adjustment each time and cycle (gentle purge) the regulator a couple of times to see the effect of your adjustment.
  • We recommend performing your tests at both low and high pressure and try to adjust your settings so that at both low and high pressure all parameters fall into the acceptable and recommended range. This might take a little skill to achieve and a good understanding of how the intermediate pressure reacts to changing supply pressures and how the cracking effort will react to different intermediate pressures.
  • Relationship of the intermediate pressure to the supply pressure:
    • For unbalanced piston first stages, the intermediate pressure will drop as the supply pressure drops.
    • For unbalanced diaphragm first stages, the intermediate pressure will rise as the supply pressure drops.
    • For balanced first stages: the intermediate pressure is stable and doesn’t change regardless of the supply pressure.
    • However, for the over balanced types of balanced first stages (example: Scubapro MK25 EVO), the intermediate pressure will rise as the supply pressure drops. This increase is noticeable but not as pronounced as unbalanced piston first stages. This type of overbalancing is NOT to be confused with over balancing terminology used to describe a faster increase in intermediate pressure as the depth increases due to the use of environmental seals compared to a ‘classic balanced’ model.
  • There is an inverse relationship of the cracking effort to intermediate pressure: - for the same setting of a second stage - if the intermediate pressure drops, the cracking effort will rise and as the intermediate pressure rises, the cracking effort will drop.
  • Complete your test in a logical sequence especially if you decide to test at both low and high pressure. Start for instance at low pressure: measure the IP and cracking effort of the primary seconds stage and octopus; then go to high pressure and measure the cracking effort of the octopus, the primary second stage and the intermediate pressure. A logical sequence will prevent you going back and forward and lose valuable time.
  • It never hurts to take a couple breaths of air from the regulator set to get a feel on how the regulator breathes and if it feels normal.

Step 8: Quality control and return the equipment to the customer.

Before you consider the job entirely completed, we like to live by the ‘golden rule’: don’t return the regulator to the customer if you’re not willing to dive it yourself. We sincerely hope you will accept this rule as well.

Time to wrap it all up, but not before some final quality assurance checks are completed. We recommend you to make your own list and incorporate those checks as ‘tick-box’ items on your worksheet.  Some examples of your final checks / tick-boxes:

  • Are all parts installed? This should be easily verified as there should be no more parts left in the smaller boxes.
  • Did you tighten all port plugs and hoses?
  • Go over all components of each stage and the entire set and try to unscrew them by hand, if you can’t then most likely all is tight.
  • Did you bag all replaced parts for the customer?
  • Did you service all hoses?

Once you completely satisfied, complete your worksheet, make your invoice, and inform your customer that you have competed the job and it’s ready for collection. The box containing the regulator set can now be placed on the ‘completed jobs’ rack.

When the customer picks up the gear, you can explain what you did and possibly give him some recommendations. We always write the recommendation on the booking form – if the nature of the job mandates this -. We also like to give the customer a copy of the worksheet.

Have the customer also sign the booking for having collected the set. If a third party collects the gear, make sure they are authorised to do so and it would be wise to take some extra precautions just in case. This might sound paranoid, but one day someone will come and claim their equipment 3-years after it has been collected, and yes, this has happened to us.


Nothing contained in these notes or shall be construed to over-ride or replace the relevant standards or manufacturer’s recommendations, manuals, data or product specific training. The contents are believed to be correct to the best of our knowledge and are offered in good faith. No warranty is expressed or implied. The author, Scuba Clinic Co., Ltd. accept no liability for any loss, damage or injury however caused resulting from information contained in these notes. It is the responsibility of the reader to verify the correct information, practices and procedures prior to commencing work.





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